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Chapter: 8 -Problem: 17 >> Examine the network motifs in Figure Q8–5. Decide which ones are negative feedback loops and which are positive. Explain your reasoning. Figure Q8-5 Transcribed Image Text: (A) ACTIVATING (B) ACTIVATING INPUT INPUT GENE X GENE X GENE Y GENE Y GENE Z GENE Z (C) ACTIVATING (D) ACTIVATING INPUT INPUT G
Answer Preview: In the network A B and C are positive feedback loops and D is a negative feed…

, Chapter: 6 -Problem: 12 >> Both hsp60-like and hsp70 molecular chaperones share an affinity for exposed hydrophobic patches on proteins, using them as indicators of incomplete folding. Why do you suppose hydrophobic patches serve as critical signals for the folding status of a protein?
Answer Preview: The cytosolic has a large amount of water that makes it a hydrophilic environment …

, Chapter: 4 -Problem: 13 >> Look at the two yeast colonies in Figure Q4–3. Each of these colonies contains about 100,000 cells descended from a single yeast cell, originally somewhere in the middle of the clump. A white colony arises when the Ade2 gene is expressed from its normal chromosomal location. When the Ade2 gene is moved to a location near a telomere, it is packed into heterochromatin and inactivated in most cells,
Answer Preview: Result Ade2 Gene Description Ade2 gene encodes P ribosyl aminoimidazole carboxylases in the de n…

, Chapter: 6 -Problem: 11 >> Prokaryotes and eukaryotes both protect against the dangers of translating broken mRNAs. What dangers do partial mRNAs pose for the cell?
Answer Preview: Partial mRNAs quite simply aren t translated because that …

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, Chapter: 2 -Problem: 17 >> In the absence of oxygen, cells consume glucose at a high, steady rate. When oxygen is added, glucose consumption drops precipitously and is then maintained at the lower rate. Why is glucose consumed at a high rate in the absence of oxygen and at a low rate in its presence?
Answer Preview: In this process there are only 2 ATP process So th…

, Chapter: 4 -Problem: 7 >> A segment of DNA from the interior of a single strand is shown in Figure Q4–1. What is the polarity of this DNA from top to bottom? Figure Q4-1 Transcribed Image Text: A CH20. 0-p-O CH20 O-P=O CH20.
Answer Preview: Polarity of this strand from top to bottom …

, Chapter: 3 -Problem: 18 >> Synthesis of the purine nucleotides AMP and GMP proceeds by a branched pathway starting with ribose 5-phosphate (R5P), as shown schematically in Figure Q3–4. Using the principles of feedback inhibition, propose a regulatory strategy for this pathway that ensures an adequate supply of both AMP and GMP and minimizes the buildup of the intermediates (A–I) when supplies of AMP and GMP are adequate. Fi
Answer Preview: In this adequate the cell response to lots of products which slow down the produc…

, Chapter: 3 -Problem: 14 >> The protein SmpB binds to a special species of tRNA, tmRNA, to eliminate the incomplete proteins made from truncated mRNAs in bacteria. If the binding of SmpB to tmRNA is plotted as fraction tmRNA bound versus SmpB concentration, one obtains a symmetrical S-shaped curve as shown in Figure Q3–3. This curve is a visual display of a very useful relationship between Kd and concentration, which has bro
Answer Preview: Using the relationship between the concentration of SmpB protein SmpB dissociation constant K d and …

, Chapter: 3 -Problem: 16 >> The enzyme hexokinase adds a phosphate to D-glucose but ignores its mirror image, L-glucose. Suppose that you were able to synthesize hexokinase entirely from D amino acids, which are the mirror image of the normal L-amino acids.A. Assuming that the “D” enzyme would fold to a stable conformation, what relationship would you expect it to bear to the normal “L” enzyme?B. Do you suppose the “D” enzym
Answer Preview: D glucose are naturally occurring sugars and the body can me…

, Chapter: 3 -Problem: 1 >> Each strand in a ? sheet is a helix with two amino acids per turn. Is the statement true? Explain why or why not.
Answer Preview: Each strand in a beta sheet is a helix …

, Chapter: 6 -Problem: 10 >> Which of the following mutational changes would you predict to be the most deleterious to gene function? Explain your answers.1. Insertion of a single nucleotide near the end of the coding sequence.2. Removal of a single nucleotide near the beginning of the coding sequence.3. Deletion of three consecutive nucleotides in the middle of the coding sequence.4. Substitution of one nucleotide for anothe
Answer Preview: The mutations given will have the following effects on the protein amino acid sequence Insertion of …

, Chapter: 8 -Problem: 3 >> If each cycle of PCR doubles the amount of DNA synthesized in the previous cycle, then 10 cycles will give a 103-fold amplification, 20 cycles will give a 106-fold amplification, and 30 cycles will give a 109-fold amplification. Is the statement true? Explain why or why not.
Answer Preview: This statement is true and false True the multiple of …

, Chapter: 5 -Problem: 2 >> In E. coli, where the replication fork travels at 500 nucleotide pairs per second, the DNA ahead of the fork— in the absence of topoisomerase would have to rotate at nearly 3000 revolutions per minute. Is the statement true? Explain why or why not.
Answer Preview: The given statement is true The parental double …

, Chapter: 6 -Problem: 3 >> Wobble pairing occurs between the first position in the codon and the third position in the anticodon. Is the statement true? Explain why or why not.
Answer Preview: The statement is False Wobble pairing is one of the types of …

, Chapter: 3 -Problem: 6 >> Enzymes that undergo cooperative allosteric transitions invariably consist of symmetric assemblies of multiple subunits. Is the statement true? Explain why or why not.
Answer Preview: Yes the statement is true The cooperative allosteric transition consists of bi…

, Chapter: 8 -Problem: 4 >> To judge the biological importance of an interaction between protein A and protein B, we need to know quantitative details about their concentrations, affinities, and kinetic behaviors. Is the statement true? Explain why or why not.
Answer Preview: True The magnitude of the apparent dissociation constant may b…

, Chapter: 4 -Problem: 10 >> Assuming that the 30-nm chromatin fiber contains about 20 nucleosomes (200 bp/nucleosome) per 50 nm of length, calculate the degree of compaction of DNA associated with this level of chromatin structure. What fraction of the 10,000-fold condensation that occurs at mitosis does this level of DNA packing represent?
Answer Preview: In above question we have to find condensation For that first we have to calculate distance of …

, Chapter: 8 -Problem: 16 >> You have just gotten back the results from an RNAseq analysis of mRNAs from liver. You had anticipated counting the number of reads of each mRNA to determine the relative abundance of different mRNAs. But you are puzzled because many of the mRNAs have given you results like those shown in Figure Q8–4. How is it that different parts of an mRNA can be represented at different levels? Figure Q8-4
Answer Preview: Different parts of the same mRNA can have different abundance …

, Chapter: 7 -Problem: 7 >> What are the two fundamental components of a genetic switch?
Answer Preview: Answer The two fundamental components of Genetic swi…

, Chapter: 3 -Problem: 15 >> Many enzymes obey simple Michaelis–Menten kinetics, which are summarized by the equation rate = Vmax [S]/([S] + Km)where Vmax = maximum velocity, [S] = concentration of substrate, and Km = the Michaelis constant.It is instructive to plug a few values of [S] into the equation to see how rate is affected. What are the rates for [S] equal to zero, equal to Km, and equal to infinite concentration?
Answer Preview: The enzymes obeying the simple Michaelis Menten equation show that the velocity of enzyme catalyzed reaction is proportional to the concentration of s…

, Chapter: 5 -Problem: 3 >> In a replication bubble, the same parental DNA strand serves as the template strand for leading-strand synthesis in one replication fork and as the template for lagging-strand synthesis in the other fork. Is the statement true? Explain why or why not.
Answer Preview: Dear students The statement is true The two complementary strands of DNA separate at the site of r…

, Chapter: 5 -Problem: 8 >> Discuss the following statement: “Primase is a sloppy enzyme that makes many mistakes. Eventually, the RNA primers it makes are replaced with DNA made by a polymerase with higher fidelity. This is wasteful. It would be more energy-efficient if a DNA polymerase made an accurate copy in the first place.”
Answer Preview: RNA primers are short fragments of RNA consisting of abo…

, Chapter: 5 -Problem: 10 >> The laboratory you joined is studying the life cycle of an animal virus that uses circular, double-strand DNA as its genome. Your project is to define the location of the origin(s) of replication and to determine whether replication proceeds in one or both directions away from an origin (unidirectional or bidirectional replication). To accomplish your goal, you broke open cells infected with the v
Answer Preview: 1 There are MULTIPLE ORIGIN OF REPLICATION in the viral DNA This could be …

, Chapter: 8 -Problem: 12 >> You want to amplify the DNA between the two stretches of sequence shown in Figure Q8–3. Of the listed primers, choose the pair that will allow you to amplify the DNA by PCR. Figure Q8-3 Transcribed Image Text: DNA to be amplified 5'-GACCTGTGGAAGC- -?????GGGA?TGA-3' 3'-CTGGACACCTTCG- GTATGCCCT????-5'
Answer Preview: DNA to be amplified 5 1 GACCTNTGGAAGC CATACGGGATTGA 3 1 3 1 CTGGACACCTTCG GTATGCCCTAACT …

, Chapter: 7 -Problem: 2 >> Once cells have differentiated to their final specialized forms, they never again alter expression of their genes. Is the statement true? Explain why or why not.
Answer Preview: The given statement is wrong as it cannot apply in all the living cells som…

, Chapter: 6 -Problem: 15 >> If an RNA molecule could form a hairpin with a symmetric internal loop, as shown in Figure Q6–5, could the complement of this RNA form a similar structure? If so, would there be any regions of the two structures that are identical? Which ones? Figure Q6-5 Transcribed Image Text: C-U 5'-G-C-A C-C-G.
Answer Preview: a Yes the complement of this R…

, Chapter: 6 -Problem: 7 >> You have attached an RNA polymerase molecule to a glass slide and have allowed it to initiate transcription on a template DNA that is tethered to a magnetic bead as shown in Figure Q6–2. If the DNA with its attached magnetic bead moves relative to the RNA polymerase as indicated in the figure, in which direction will the bead rotate? Figure Q6–2
Answer Preview: The bead must rotate in anti clockwise direction The reason beind …

, Chapter: 5 -Problem: 13 >> With age, somatic cells are thought to accumulate genomic “scars” as a result of the inaccurate repair of double- strand breaks by nonhomologous end joining (NHEJ).Estimates based on the frequency of breaks in primary human fibroblasts suggest that by age 70, each human somatic cell may carry some 2000 NHEJ-induced mutations due to inaccurate repair. If these mutations were distributed randomly ar
Answer Preview: Nonhomologous end joining is a quick but no so efficient solution for repairing double strand breaks …

, Chapter: 19 -Problem: 8 >> It is not an easy matter to assign particular functions to specific components of the basal lamina, since the overall structure is a complicated composite material with both mechanical and signaling properties. Nidogen, for example, cross-links two central components of the basal lamina by binding to the laminin ?-1 chain and to type IV collagen. Given such a key role, it was surprising that mice
Answer Preview: Common problem facing any business entity is the debt versus equity d…

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, Chapter: 17 -Problem: 11 >> How many kinetochores are there in a human cell at mitosis?
Answer Preview: Correct answer: 92 kinetochores For every chrom…

, Chapter: 3 -Problem: 13 >> An antibody binds to another protein with an equilibrium constant, K, of 5 × 109 M–1. When it binds to a second, related protein, it forms three fewer hydrogen bonds, reducing its binding affinity by 11.9 kJ/mole. What is the K for its binding to the second protein? (Free-energy change is related to the equilibrium constant by the equation ?G° = –2.3 RT log K, where R is 8.3 × 10–3 kJ/(mole K) and
Answer Preview: Answer Equilibrium constant K for its binding to second protein 4 6 10 …

, Chapter: 17 -Problem: 3 >> While other proteins come and go during the cell cycle, the proteins of the origin recognition complex remain bound to the DNA throughout. Which statements are true? Explain why or why not.
Answer Preview: ORC(Origin Recognition Complex) is a central component for …

, Chapter: 3 -Problem: 2 >> Intrinsically disordered regions of proteins can be identified using bioinformatic methods to search genes for encoded amino acid sequences that possess high hydrophobicity and low net charge. Is the statement true? Explain why or why not.
Answer Preview: The given statement is false because intrinsically disordered regions IDRs possess low hydrophobicit…

, Chapter: 19 -Problem: 13 >> Your boss is coming to dinner! All you have for a salad is some wilted, day-old lettuce. You vaguely recall that there is a trick to rejuvenating wilted lettuce, but you cannot remember what it is. Should you soak the lettuce in salt water, soak it in tap water, or soak it in sugar water, or maybe just shine a bright light on it and hope that photosynthesis will perk it up?
Answer Preview: A day older lettuce can be rejuvenate by dip…

, Chapter: 8 -Problem: 2 >> Given the inexorable march of technology, it seems inevitable that the sensitivity of detection of molecules will ultimately be pushed beyond the yoctomole level (10–24 mole).     Is the statement true? Explain why or why not.
Answer Preview: It is false The sensitivity of detection of molecules will u…

, Chapter: 19 -Problem: 14 >> A plant must be able to respond to changes in the water status of its surroundings. It does so by the flow of water molecules through water channels called aquaporins. The hydraulic conductivity of a single aquaporin is 4.4 × 10–22 m3 per second per MPa (megapascal) of pressure. What does this correspond to in terms of water molecules per second at atmospheric pressure? [Atmospheric pressure is 0.
Answer Preview: Hydraulic conductivity of aquaporin = 4 4 10 -23 m 3 /sec/Mpa Means at 1 MPa hydraulic co…

, Chapter: 5 -Problem: 15 >> In addition to correcting DNA mismatches, the mismatch repair system functions to prevent homologous recombination from taking place between similar but not identical sequences. Why would recombination between similar, but nonidentical sequences pose a problem for human cells?
Answer Preview: The inactivation of mutations manifests a greater i…

, Chapter: 23 -Problem: 14 >> Avian influenza viruses readily infect birds, but are transmitted to humans very rarely. Similarly, human influenza viruses spread readily to other humans, but have never been detected in birds. The key to this specificity lies in the viral capsid protein, hemagglutinin, which binds to sialic acid residues on cell-surface glycoproteins, triggering virus entry into the cell (Movie 23.8). Hemaggluti
Answer Preview: As pigs make carbohydrate chains with both linkages of …

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, Chapter: 19 -Problem: 7 >> The food-poisoning bacterium Clostridium perfringens makes a toxin that binds to members of the claudin family of proteins, which are the main constituents of tight junctions. When the C-terminus of the toxin is bound to a claudin, the N-terminus can insert into the adjacent cell membrane, forming holes that kill the cell. The portion of the toxin that binds to the claudins has proven to be a valu
Answer Preview: A. Toxin does not affect claudin-1. Even if claudin- 4 has disappeared, claudin- 1 …

, Chapter: 6 -Problem: 13 >> Most proteins require molecular chaperones to assist in their correct folding. How do you suppose the chaperones themselves manage to fold correctly?
Answer Preview: Chaperons proteins plays an important role in stabilizing the tertiary and quaternary or 4 structure of protein The proteins formed up of amino acid a…

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, Chapter: 18 -Problem: 5 >> Imagine that you could microinject cytochrome c into the cytosol of wild-type mammalian cells and of cells that were doubly defective for Bax and Bak. Would you expect one, both, or neither type of cell to undergo apoptosis? Explain your reasoning.
Answer Preview: Dear students, Apoptosis means ' programmed cell death '. In the intrinsic pathway of apoptosis wh…

, Chapter: 3 -Problem: 7 >> Continual addition and removal of phosphates by protein kinases and protein phosphatases is wasteful of energy—since their combined action consumes ATP— but it is a necessary consequence of effective regulation by phosphorylation. Is the statement true? Explain why or why not.
Answer Preview: Nothing is put to waste because the constant cycling makes the regulated pr…

, Chapter: 21 -Problem: 3 >> As development progresses, individual cells become more and more restricted in the range of cell types they can give rise to. Which statements are true? Explain why or why not.
Answer Preview: As development progresses, the cells become confined to a range in which they produce similar types …

, Chapter: 6 -Problem: 14 >> What is so special about RNA that it is hypothesized to be an evolutionary precursor to DNA and protein? What is it about DNA that makes it a better material than RNA for storage of genetic information?
Answer Preview: RNA is thought to be the precursor genetic molecule primarily due to the following factors 1 Its str…

, Chapter: 18 -Problem: 3 >> One important role of Fas and Fas ligand is to mediate the elimination of tumor cells by killer lymphocytes. In a study of 35 primary lung and colon tumors, half the tumors were found to have amplified and overexpressed a gene for a secreted protein that binds to Fas ligand. How do you suppose that overexpression of this protein might contribute to the survival of these tumor cells? Explain your r
Answer Preview: Fas ligand and its receptor belong to the tumor necrosis factor (TNF) family of proteins and play an …

, Chapter: 5 -Problem: 12 >> If you compare the frequency of the sixteen possible dinucleotide sequences in the E. coli and human genomes, there are no striking differences except for one dinucleotide, 5?-CG-3?. The frequency of CG dinucleotides in the human genome is significantly lower than in E. coli and significantly lower than expected by chance. Why do you suppose that CG dinucleotides are underrepresented in the human
Answer Preview: In the human genome CG dinucleotides are the least persistent and these …

, Chapter: 20 -Problem: 3 >> Cancer therapies directed solely at killing the rapidly dividing cells that make up the bulk of a tumor are unlikely to eliminate the cancer from many patients. Which statements are true? Explain why or why not.
Answer Preview: The statement; Cancer therapies directed solely at killing the rapidly dividing cells that make up the bulk of a tumor are unlikely to eliminate the c…

, Chapter: 3 -Problem: 5 >> Higher concentrations of enzyme give rise to a higher turnover number. Is the statement true? Explain why or why not.
Answer Preview: It is false The turn over number does not depend on t…

, Chapter: 23 -Problem: 2 >> The microbiomes from healthy humans are all very similar. Which statements are true? Explain why or why not.
Answer Preview: This statement is wrong. Because even healthy humans may have a difference …

, Chapter: 8 -Problem: 6 >> After a sudden increase in transcription, a protein with a slow rate of degradation will reach a new steady state level more quickly than a protein with a rapid rate of degradation. Is the statement true? Explain why or why not.
Answer Preview: False Because the rate of degradation is not the only factor that …

, Chapter: 20 -Problem: 8 >> Virtually all cancer treatments are designed to kill cancer cells, usually by inducing apoptosis. However, one particular cancer—acute promyelocytic leukemia (APL)— has been successfully treated with all trans-retinoic acid, which causes the promyelocytes to differentiate into neutrophils. How might a change in the state of differentiation of APL cancer cells help the patient?
Answer Preview: Promyelocytes are premature granulocytes, which upon maturation form neut…

, Chapter: 2 -Problem: 13 >> Polymerization of tubulin subunits into microtubules occurs with an increase in the orderliness of the subunits. Yet tubulin polymerization occurs with an increase in entropy (decrease in order). How can that be?
Answer Preview: tubulin subunits are slughtly hydrophobic they order the wa…

, Chapter: 21 -Problem: 2 >> Because of the many later developmental transformations that produce the elaborately structured organs, the body plan set up during gastrulation bears little resemblance to the body plan in the adult. Which statements are true? Explain why or why not.
Answer Preview: It is false because during the embryonic period that is approxima…

, Chapter: 4 -Problem: 14 >> Mobile pieces of DNA—transposable elements— that insert themselves into chromosomes and accumulate during evolution make up more than 40% of the human genome. Transposable elements of four types—long interspersed nuclear elements (LINEs), short interspersed nuclear elements (SINEs), long terminal repeat (LTR) retrotransposons, and DNA transposons—are inserted more-or-less randomly throughout the h
Answer Preview: Transposons are rare in hox clusters to prevent disturbances in the tightly regulated Spatio tempora…

, Chapter: 22 -Problem: 7 >> The origin of new ? cells of the pancreas—from stem cells or from preexisting ? cells—was not resolved until a decade ago, when the technique of lineage tracing was used to decide the issue. Using transgenic mice that expressed a tamoxifen-activated form of Cre recombinase under the control of the insulin promoter, which is active only in ? cells, investigators could remove an inhibitory segment o
Answer Preview: A cell expressing HPAP 100 80 60 40 HHHH 20 O 0506 0 4 6 9 12 TXI Insolent Promot…

, Chapter: 7 -Problem: 1 >> In terms of the way it interacts with DNA, the helix–loop–helix motif is more closely related to the leucine zipper motif than it is to the helix turn–helix motif. Is the statement true? Explain why or why not.
Answer Preview: The statement is True Explanation We know that the leucine zipper m…

, Chapter: 23 -Problem: 12 >> Influenza epidemics account for 250,000 to 500,000 deaths globally each year. These epidemics are markedly seasonal, occurring in temperate climates in the northern and southern hemispheres during their respective winters. By contrast, in the tropics, there is significant influenza activity year round, with a peak in the rainy season (Figure Q23–3). Can you suggest some possible explanations for t
Answer Preview: TROPICS Tropics are defined as the geographical area lying between 26 5 degrees N an…

, Chapter: 5 -Problem: 9 >> If DNA polymerase requires a perfectly paired primer in order to add the next nucleotide, how is it that any mismatched nucleotides “escape” this requirement and become substrates for mismatch repair enzymes?
Answer Preview: When a mismatched occurred the proofreading which was carried out by DNA polymerase would often unde…

, Chapter: 5 -Problem: 7 >> DNA repair enzymes preferentially repair mismatched bases on the newly synthesized DNA strand, using the old DNA strand as a template. If mismatches were instead repaired without regard for which strand served as template, would mismatch repair reduce replication errors? Would such a mismatch repair system result in fewer mutations, more mutations, or the same number of mutations as there would ha
Answer Preview: The mismatch repair enzymes mutS and mutL in prokaryotes like E coli identify the mismatch bases in …

, Chapter: 8 -Problem: 19 >> Detailed analysis of the regulatory region of the Lac operon has revealed surprising complexity. Instead of a single binding site for the Lac repressor, as might be expected, there are three sites termed operators: O1, O2, and O3, arrayed along the DNA as shown in Figure Q8–7. To probe the functions of these three sites, you make a series of constructs in which various combinations of operator sit
Answer Preview: 1 The single most important operator site here is the O 1 As presence of O 1 significan…

, Chapter: 5 -Problem: 11 >> You are investigating DNA synthesis in tissue-culture cells, using 3H-thymidine to radioactively label the replication forks. By breaking open the cells in a way that allows some of the DNA strands to be stretched out, very long DNA strands can be isolated intact and examined. You overlay the DNA with a photographic emulsion, and expose it for 3 to 6 months, a procedure known as autoradiography.Be
Answer Preview: A In case of dense region there is more concentration of 3H thymidine which show…

, Chapter: 17 -Problem: 7 >> Many cell-cycle genes from human cells function perfectly well when expressed in yeast cells. Why do you suppose that is considered remarkable? After all, many human genes encoding enzymes for metabolic reactions also function in yeast, and no one thinks that is remarkable.
Answer Preview: The enzymatic competence does not rely on critical …

, Chapter: 3 -Problem: 10 >> The so-called kelch motif consists of a fourstranded ? sheet, which forms what is known as a ? propeller. It is usually found to be repeated four to seven times, forming a kelch repeat domain in a multidomain protein.One such kelch repeat domain is shown in Figure Q3–1. Would you classify this domain as an “in-line” or “plug-in” type domain?
Answer Preview: Various Proteins comprised of different types of protein domains which the characteristics of the te…

, Chapter: 21 -Problem: 6 >> The cell cycle is the ticking clock that sets the tempo of developmental processes, with maturational changes in gene expression being dependent on cell-cycle progression. Which statements are true? Explain why or why not.
Answer Preview: The above statement is false because this is n…

, Chapter: 3 -Problem: 17 >> How do you suppose that a molecule of hemoglobin is able to bind oxygen efficiently in the lungs, and yet release it efficiently in the tissues?
Answer Preview: Haemoglobin Hb is a complex protien of quarternary structure with subunits which are noncovalently l…

, Chapter: 22 -Problem: 10 >> Generation of induced pluripotent stem (iPS) cells was first accomplished using retroviral vectors to carry the OSKM (Oct4, Sox2, Klf4, and Myc) set of transcription regulators into cells. The efficiency of fibroblast reprogramming was typically low (0.01%), in part because large numbers of retroviruses must integrate to bring about reprogramming and each integration event carries with it the risk
Answer Preview: Reprogramming is the method of re-converting mature and established cells into induced pluripotent s…

, Chapter: 8 -Problem: 9 >> Hybridoma technology allows one to generate monoclonal antibodies to virtually any protein. Why is it, then, that genetically tagging proteins with epitopes is such a commonly used technique, especially since an epitope tag has the potential to interfere with the function of the protein?
Answer Preview: Hybridism Technology is a method for producing a large number of identica…

, Chapter: 19 -Problem: 1 >> Given the numerous processes inside cells that are regulated by changes in Ca2+ concentration, it seems likely that Ca2+-dependent cell–cell adhesions are also regulated by changes in Ca2+ concentration. Which statements are true? Explain why or why not.
Answer Preview: Cell to cell adhesions is affected by Calcium so…

, Chapter: 4 -Problem: 5 >> Gene duplication and divergence is thought to have played a critical role in the evolution of increased biological complexity. Is the statement true? Explain why or why not.
Answer Preview: Yes the statement is true because the duplicated genes can have different …

, Chapter: 24 -Problem: 2 >> To guarantee that the antigen-presenting cells in the thymus will display a complete repertoire of self peptides to allow elimination of self-reactive T cells, the thymus recruits dendritic cells from all over the body. Which statements are true? Explain why or why not.
Answer Preview: This is a false statement. The thymic e…

, Chapter: 4 -Problem: 6 >> DNA isolated from the bacterial virus M13 contains 25% A, 33% T, 22% C, and 20% G. Do these results strike you as peculiar? Why or why not? How might you explain these values?
Answer Preview: Yes it strick me peculiar but the result is correct Viruses have RNA as it s the genetic …

, Chapter: 23 -Problem: 17 >> When the Oxford team of Ernst Chain and Norman Heatley had laboriously collected their first two grams of penicillin (probably no more than 2% pure!), Chain injected two normal mice with 1 g each of this preparation, and waited to see what would happen. The mice survived with no apparent ill effects. Their boss, Howard Florey, was furious at what he saw as a waste of good antibiotic. Why was this
Answer Preview: Alexander flaming whiz working on staphylococci bacteri…

, Chapter: 3 -Problem: 4 >> An enzyme reaches a maximum rate at high substrate concentration because it has a fixed number of active sites where substrate binds. Is the statement true? Explain why or why not.
Answer Preview: The rate of reaction increases with the increased substrate concentration An opt…

, Chapter: 21 -Problem: 17 >> The highly branched structures of neurons would seem to make it almost inevitable that they should make unproductive synapses with themselves, yet they manage to avoid this outcome very effectively. How is this accomplished in vertebrates?
Answer Preview: Vertebrates are a complex form of being which is formed together by different systems or cells th…

, Chapter: 3 -Problem: 11 >> Titin, which has a molecular weight of about 3 × 106, is the largest polypeptide yet described. Titin molecules extend from muscle thick filaments to the Z disc; they are thought to act as springs to keep the thick filaments centered in the sarcomere. Titin is composed of a large number of repeated immunoglobulin (Ig) sequences of 89 amino acids, each of which is folded into a domain about 4 nm in
Answer Preview: Titin spring like behaviour of sequential unfolding of IG do…

, Chapter: 19 -Problem: 4 >> Integrins can convert mechanical signals into intracellular molecular signals. Which statements are true? Explain why or why not.
Answer Preview: The answer is true. Tension cause to an integrin that can cause it to tighten its gr…

, Chapter: 4 -Problem: 3 >> Nucleosomes bind DNA so tightly that they cannot move from the positions where they are first assembled. Is the statement true? Explain why or why not.
Answer Preview: False It is a well known fact that nucleosomes and DNA d…

, Chapter: 20 -Problem: 11 >> The Tasmanian devil, a carnivorous Australian marsupial, is threatened with extinction by the spread of a fatal disease in which a malignant oral–facial tumor interferes with the animal’s ability to feed. You have been called in to analyze the source of this unusual cancer. It seems clear to you that the cancer is somehow spread from devil to devil, very likely by their frequent fighting, which is
Answer Preview: It is transferred from devil to devil and it can be a infec…

, Chapter: 6 -Problem: 2 >> Since introns are largely genetic “junk,” they do not have to be removed precisely from the primary transcript during RNA splicing. Is the statement true? Explain why or why not.
Answer Preview: This statement is False Explanation The splicing of RNA is very complicated and crucial Du…

, Chapter: 23 -Problem: 10 >> The intracellular bacterial pathogen Salmonella typhimurium, which causes gastroenteritis, injects effector proteins to promote its invasion into nonphagocytic host cells by the trigger mechanism. S. typhimurium first stimulates membrane ruffling to promote invasion, and then suppresses membrane ruffling once invasion is complete. This behavior is mediated in part by injection of two effector prot
Answer Preview: (a) Samonellas invasion of host cell depends on S almonella p athogenicity i sland 1 (SPI1) region i…

, Chapter: 8 -Problem: 8 >> Tropomyosin, at 93 kd, sediments at 2.6S, whereas the 65-kd protein, hemoglobin, sediments at 4.3S. (The sedimentation coefficient S is a linear measure of the rate of sedimentation.) These two proteins are drawn to scale in Figure Q8–1. How is it that the bigger protein sediments more slowly than the smaller one? Can you think of an analogy from everyday experience that might help you with this p
Answer Preview: Bigger the particle or protein size more gravitational or centrifugal force it is acted …

, Chapter: 22 -Problem: 5 >> In the 1950s, scientists fed 3H-thymidine to rats to label cells that were synthesizing DNA, and then followed the fates of labeled cells for periods of up to a year. They found three patterns of cell labeling in different tissues. Cells in some tissues such as neurons in the central nervous system and the retina did not get labeled. Muscle, kidney, and liver, by contrast, each showed a small numb
Answer Preview: As we know that 3 H-thymidine is used for determining r…

, Chapter: 4 -Problem: 2 >> The four core histones are relatively small proteins with a very high proportion of positively charged amino acids; the positive charge helps the histones bind tightly to DNA, regardless of its nucleotide sequence. Which statements are true? Explain why or why not.
Answer Preview: The statement in the question is true The explanation below proove that the positive charge in histo…

, Chapter: 24 -Problem: 10 >> At first glance, it would seem a dangerous strategy for the thymus to actively promote the survival, maturation, and emigration of developing T cells that bind weakly to self peptides bound to self MHC molecules. Would it not be safer to get rid of these T cells, along with those that bind strongly to such self-peptide–MHC complexes, as this would seem a more secure way to avoid autoimmune reactio
Answer Preview: - During the fetal stage of development, our body produces clones that …

, Chapter: 6 -Problem: 4 >> During protein synthesis, the thermodynamics of base-pairing between tRNAs and mRNAs sets the upper limit for the accuracy with which protein molecules are made. Is the statement true? Explain why or why not.
Answer Preview: During protein synthesis the thermodynamics of base pai…

, Chapter: 22 -Problem: 6 >> At any given time, intestinal crypts of mice comprise about 15 stem cells and 10 Paneth cells. After cell division, which occurs about once a day, the daughter cells remain stem cells only if they maintain contact with a Paneth cell. This constant competition for Paneth-cell contact raises the possibility that crypts might become monoclonal over time; that is, the crypt cells at one point in time
Answer Preview: Crypt cell consist of stem cells and paneth cells. Stem cel…

, Chapter: 7 -Problem: 11 >> Imagine the two situations shown in Figure Q7–2. In cell 1, a transient signal induces the synthesis of protein A, which is a transcription activator that turns on many genes including its own. In cell 2, a transient signal induces the synthesis of protein R, which is a transcription repressor that turns off many genes including its own. In which, if either, of these situations will the descendant
Answer Preview: In cell I the gene is being activated leading to the synthesis …

, Chapter: 19 -Problem: 2 >> Tight junctions perform two distinct functions: they seal the space between cells to restrict paracellular flow and they fence off plasma membrane domains to prevent the mixing of apical and basolateral membrane proteins. Which statements are true? Explain why or why not.
Answer Preview: Tight junction performs two distinct functions;they seal the space between cells to restrict paracel…

, Chapter: 7 -Problem: 3 >> CG islands are thought to have arisen during evolution because they were associated with portions of the genome that remained unmethylated in the germ line. Is the statement true? Explain why or why not.
Answer Preview: The given statement about CG is correct CpG dinucleotides are found unevenly distri…

, Chapter: 17 -Problem: 10 >> High doses of caffeine interfere with the DNA damage response in mammalian cells. Why then do you suppose the Surgeon General has not yet issued an appropriate warning to heavy coffee and cola drinkers? A typical cup of coffee (150 mL) contains 100 mg of caffeine (196 g/ mole). How many cups of coffee would you have to drink to reach the dose (10 mM) required to interfere with the DNA damage respo
Answer Preview: Total water - 40 litre 40 10 = 400 mM 400 millimole of caffeine is needed t…

, Chapter: 3 -Problem: 8 >> Consider the following statement. “To produce one molecule of each possible kind of polypeptide chain, 300 amino acids in length, would require more atoms than exist in the universe.” Given the size of the universe, do you suppose this statement could possibly be correct? Since counting atoms is a tricky business, consider the problem from the standpoint of mass. The mass of the observable univers
Answer Preview: Answer We know a polypeptide Chain formed from amino acids Now given numbers of amino acids in po…

, Chapter: 21 -Problem: 1 >> In the early cleavage stages, when the embryo cannot yet feed, the developmental program is driven and controlled entirely by the material deposited in the egg by the mother. Which statements are true? Explain why or why not.
Answer Preview: Cleavage formation takes place rapid cell multiplication by mitosis . It is a early division which o…

, Chapter: 8 -Problem: 11 >> You have isolated the proteins from two adjacent spots after two-dimensional polyacrylamide-gel electrophoresis and digested them with trypsin. When the masses of the peptides were measured by MALDI-TOF mass spectrometry, the peptides from the two proteins were found to be identical except for one (Figure Q8–2). For this peptide, the mass-to-charge (m/z) values differed by 80, a value that does no
Answer Preview: MALDI TOF mass spectrometers are now commonplace and their relative ease of use …

, Chapter: 22 -Problem: 4 >> Disturbance of the balance in the activities of osteoblasts and osteoclasts in favor of osteoclasts can give rise to the condition known as osteoporosis, the brittle- bone syndrome of the elderly. Which statements are true? Explain why or why not.
Answer Preview: Dear students, In bones there are mainly 3 types of cells are present. 1 Osteo…

, Chapter: 7 -Problem: 13 >> If you insert a ?-galactosidase gene lacking its own transcription control region into a cluster of piRNA genes in Drosophila, you find that ?-galactosidase expression from a normal copy elsewhere in the genome is strongly inhibited in the fly’s germ cells. If the inactive ?-galactosidase gene is inserted outside the piRNA gene cluster, the normal gene is properly expressed. What do you suppose is
Answer Preview: Alternative selectable Markos have been developed which differentiate recombinants on …

, Chapter: 20 -Problem: 1 >> The chemical carcinogen dimethylbenz[a]anthracene (DMBA) must be an extraordinarily specific mutagen since 90% of the skin tumors it causes have an A-to-T alteration at exactly the same site in the mutant Ras gene. Which statements are true? Explain why or why not.
Answer Preview: The answer is false. The Ras gene when converted b…

, Chapter: 4 -Problem: 9 >> Chromosome 3 in orangutans differs from chromosome 3 in humans by two inversion events that occurred in the human lineage (Figure Q4–2). Draw the intermediate chromosome that resulted from the first inversion and explicitly indicate the segments included in each inversion. Transcribed Image Text: tw
Answer Preview: 1 Two overlapping inversions in the chromosome 3 homo…

, Chapter: 1 -Problem: 3 >> Most of the DNA sequences in a bacterial genome code for proteins, whereas most of the DNA sequences in the human genome do not. Which statements are true? Explain why or why not.
Answer Preview: True Bacterial genomes seem to be paired down to the essentials most of the DNA sequences enco…

, Chapter: 23 -Problem: 9 >> The Gram-negative bacterium Yersinia pestis, the causative agent of the plague, is extremely virulent. Upon infection, Y. pestis injects a set of effector proteins into macrophages that suppresses their phagocytic behavior and also interferes with their innate immune responses. One of the effector proteins, YopJ, acetylates serines and threonines on various MAP kinases, including the MAP kinase ki
Answer Preview: YopJ is immunosuppressive and proapoptotic. YopJ functions as a serine/threonine acetyl-transferase …

, Chapter: 2 -Problem: 16 >> Does a Snickers™ candy bar (65 g, 1360 kJ) provide enough energy to climb from Zermatt (elevation 1660 m) to the top of the Matterhorn (4478 m, Figure Q2–3), or might you need to stop at HÖrnli Hut (3260 m) to eat another one? Imagine that you and your gear have a mass of 75 kg, and that all of your work is done against gravity (that is, you are just climbing straight up). Remember from your intro
Answer Preview: The ideally man should stop at Hornli hut to eat extra 5 snicker because at id…

, Chapter: 2 -Problem: 5 >> Linking the energetically unfavorable reaction A ? B to a second, favorable reaction B ? C will shift the equilibrium constant for the first reaction. Is the statement true? Explain why or why not.
Answer Preview: The given statement is False This is because the equilibrium constan…

, Chapter: 19 -Problem: 3 >> The elasticity of elastin derives from its high content of ? helices, which act as molecular springs. Which statements are true? Explain why or why not.
Answer Preview: It's false It's false, because the force that deforms elas…

, Chapter: 5 -Problem: 14 >> Draw the structure of the double Holliday junction that would result from strand invasion by both ends of the broken duplex into the intact homologous duplex shown in Figure Q5–3. Label the left end of each strand in the Holliday junction 5? or 3? so that the relationship to the parental and recombinant duplexes is clear. Indicate how DNA synthesis would be used to fill in any single-strand gaps i
Answer Preview: 3 5 A a Resection stage 1st Double Strand break stage Ind DSBR 3 …

, Chapter: 23 -Problem: 6 >> In order to survive and multiply, a successful pathogen must accomplish five tasks. Name them.
Answer Preview: Pathogens are the agents which cause diseases to our body. Mainly viruses, bacteria, fungi and pa…

, Chapter: 8 -Problem: 14 >> Explain the difference between a gain-of-function mutation and a dominant-negative mutation. Why are both these types of mutation usually dominant?
Answer Preview: Gain of function mutation When dominant mutations increase the activity of given gene gene produ…

, Chapter: 18 -Problem: 7 >> When human cancer cells are exposed to ultraviolet (UV) light at 90 mJ/cm2, most of the cells undergo apoptosis within 24 hours. Release of cytochrome c from mitochondria can be detected as early as 6 hours after exposure of a population of cells to UV light, and it continues to increase for more than 10 hours thereafter. Does this mean that individual cells slowly release their cytochrome c over
Answer Preview: Mechanism of cytochrome C release from mitochondria - Cytochrome C (1) Cytochrome c is a cheap regul…

, Chapter: 8 -Problem: 7 >> A common step in the isolation of cells from a sample of animal tissue is to treat the tissue with trypsin, collagenase, and EDTA. Why is such a treatment necessary, and what does each component accomplish? And why does this treatment not kill the cells?
Answer Preview: Proteins are important messengers and anchors of information on the cell surface Proteins are majorl…

, Chapter: 23 -Problem: 16 >> In the early days of penicillin research, it was discovered that bacteria in the air could destroy the penicillin, a big problem for large-scale production of the drug. How do you suppose this occurs?
Answer Preview: Bacteria that are airborne could destroy penicillin due to their enzymes called bet…

, Chapter: 5 -Problem: 6 >> To determine the reproducibility of mutation frequency measurements, you do the following experiment. You inoculate each of 10 cultures with a single E. coli bacterium, allow the cultures to grow until each contains 106 cells, and then measure the number of cells in each culture that carry a mutation in your gene of interest. You were so surprised by the initial results that you repeated the exper
Answer Preview: 1 Mutation rates differ between species and even between different regio…

, Chapter: 22 -Problem: 1 >> In the small intestine, stem cells in the crypts divide asymmetrically to maintain the population of cells that make up the villi; after each division, one daughter remains a stem cell and the other begins to divide rapidly to produce differentiated progeny. Which statements are true? Explain why or why not.
Answer Preview: Both statements are true; as a division in the small intestine is to produc…

, Chapter: 8 -Problem: 5 >> The rate of change in the concentration of any molecular species X is given by the balance between its rate of appearance and its rate of disappearance. Is the statement true? Explain why or why not.
Answer Preview: The concentration of a substance X will remain constant …

, Chapter: 20 -Problem: 10 >> PolyADP-ribose polymerase (PARP) plays a key role in the repair of DNA single-strand breaks. In the presence of the PARP inhibitor olaparib, single-strand breaks accumulate. When a replication fork encounters a single- strand break, it converts it to a double-strand break, which in normal cells is then repaired by homologous recombination. In cells defective for homologous recombination, however,
Answer Preview: Cancer cells have a higher rate of cell division than normal cells. So in cancer cells, replication …

, Chapter: 4 -Problem: 1 >> Human females have 23 different chromosomes, whereas human males have 24. Is the statement true? Explain why or why not.
Answer Preview: It s a false statement Human male and female have the same number of c…

, Chapter: 1 -Problem: 1 >> Each member of the human hemoglobin gene family, which consists of seven genes arranged in two clusters on different chromosomes, is an ortholog to all of the other members. Which statements are true? Explain why or why not.
Answer Preview: The statement is false By definition an ortholog means that it is any of …

, Chapter: 19 -Problem: 6 >> Cell adhesion molecules were originally identified using antibodies raised against cell-surface components to block cell aggregation. In the adhesion-blocking assays, the researchers found it necessary to use antibody fragments, each with a single binding site (so-called Fab fragments), rather than intact IgG antibodies, which are Y shaped molecules with two identical binding sites. The Fab fragme
Answer Preview: The other segment of the antibody is called the Fc segment and it usually is iden…

, Chapter: 6 -Problem: 6 >> In which direction along the template must the RNA polymerase in Figure Q6–1 be moving to have generated the supercoiled structures that are shown? Would you expect supercoils to be generated if the RNA polymerase were free to rotate about the axis of the DNA as it progressed along the template? Figure Q6–1
Answer Preview: The twin supercoiled domain model describes how transcription can drive DNA s…

, Chapter: 2 -Problem: 12 >> “Diffusion” sounds slow—and over everyday distances it is—but on the scale of a cell it is very fast. The average instantaneous velocity of a particle in solution—that is, the velocity between the very frequent collisions—isv = (kT/m)½where k = 1.38 × 10–16 g cm2/K sec2, T = temperature in K (37°C is 310 K), and m = mass in g/molecule.Calculate the instantaneous velocity of a water molecule (molec
Answer Preview: 1 dalton 1g mole and 1 mole 6 022 x 10 23 molecules therefore 1 dalton 1g 6 022 x 10 23 molecules 1 …

, Chapter: 24 -Problem: 8 >> Working out the rules by which T cells interact with their target cells was complicated. Some of the key observations came from studying the way cytotoxic T cells killed cells infected with choriomeningitis virus (LCMV). Cytotoxic T cells derived from mice expressing “k-type” class I MHC proteins lysed LCMV-infected cells expressing the same k-type MHC protein, but they did not lyse infected cells
Answer Preview: Helper T cells are distinguished from cytotoxic T' cells due to presence of T- …

, Chapter: 4 -Problem: 12 >> Why is a chromosome with two centromeres (a dicentric chromosome) unstable? Would a backup centromere not be a good thing for a chromosome, giving it two chances to form a kinetochore and attach to microtubules during mitosis? Would that not help to ensure that the chromosome did not get left behind at mitosis?
Answer Preview: As we know the centromere is a unique structure that is found in the chromosome and it links a pair …

, Chapter: 1 -Problem: 4 >> Since it was deciphered four decades ago, some have claimed that the genetic code must be a frozen accident, while others have argued that it was shaped by natural selection. A striking feature of the genetic code is its inherent resistance to the effects of mutation. For example, a change in the third position of a codon often specifies the same amino acid or one with similar chemical properties.
Answer Preview: Genetic code is a frozen accident given by Crick explain the inherent power of genetic c…

, Chapter: 20 -Problem: 2 >> In the cellular regulatory pathways that control cell growth and proliferation, the products of oncogenes are stimulatory components and the products of tumor suppressor genes are inhibitory components. Which statements are true? Explain why or why not.
Answer Preview: Cancer is the uncontrolled division of cells. It may lead to formation of solid tumors or may lead t…

, Chapter: 5 -Problem: 4 >> When bidirectional replication forks from adjacent origins meet, a leading strand always runs into a lagging strand. Is the statement true? Explain why or why not.
Answer Preview: Yes the above statement is true that the replication forks proceed b…

, Chapter: 18 -Problem: 1 >> In normal adult tissues, cell death usually balances cell division. Which statements are true? Explain why or why not.
Answer Preview: The statement 'In normal adult tissues, cell death usually balances cell di…

, Chapter: 2 -Problem: 15 >> Assuming that there are 5 × 1013 cells in the human body and that ATP is turning over at a rate of 109 ATP molecules per minute in each cell, how many watts is the human body consuming? (A watt is a joule per second.) Assume that hydrolysis of ATP yields 50 kJ/mole.
Answer Preview: We know from the question that the number of cells in the human body is 5 x 10 1…

, Chapter: 21 -Problem: 10 >> Morphogens play a key role in development, creating concentration gradients that inform cells of where they are and how to behave. Examine the simple patterns represented by the flags in Figure Q21–1. Which do you suppose could be created by a gradient of a single morphogen? Which would require gradients of two morphogens? Assuming that such patterns were present in a sheet of cells, explain how t
Answer Preview: In the French flag model the French flag is used to represent the effect of a m…

, Chapter: 6 -Problem: 5 >> Protein enzymes are thought to greatly outnumber ribozymes in modern cells because they can catalyze a much greater variety of reactions and all of them have faster rates than any ribozyme. Is the statement true? Explain why or why not.
Answer Preview: The statement is False Explanation Ribosomes are kn…

, Chapter: 22 -Problem: 8 >> One of the earliest assays for hematopoietic stem cells made use of their ability to form colonies in the spleens of heavily irradiated mice. By varying the amounts of transplanted bone marrow cells, investigators showed that the number of spleen colonies varied linearly with dose and that the curve passed through the origin, suggesting that single cells were capable of forming individual colonies
Answer Preview: Bone marrow consists of 2 parts. among these is the hematopoietic cel…

, Chapter: 4 -Problem: 11 >> In contrast to histone acetylation, which always correlates with gene activation, histone methylation can lead to either transcriptional activation or repression. How do you suppose that the same modification methylation— can mediate different biological outcomes?
Answer Preview: Histone acetylation alters chromatin structure Acetylation refers to the transfer of acetyl groups f…

, Chapter: 24 -Problem: 5 >> It would be disastrous if a complement attack were not confined to the surface of the pathogen that is the target of the attack. Yet, the proteolytic cascade involved in the attack liberates biologically active molecules at several steps: one that diffuses away and one that remains bound to the target surface. How does the complement reaction remain localized when active products leave the surface
Answer Preview: Complementary DNA clones are most protein of major amplification and effector of immune host def…

, Chapter: 3 -Problem: 3 >> Loops of polypeptide that protrude from the surface of a protein often form the binding sites for other molecules. Is the statement true? Explain why or why not.
Answer Preview: The answer of your stateme…

, Chapter: 18 -Problem: 6 >> In contrast to their similar brain abnormalities, newborn mice deficient in Apaf1 or caspase-9 have distinctive abnormalities in their paws. Apaf1-deficient mice fail to eliminate the webs between their developing digits, whereas caspase-9-deficient mice have normally formed digits (Figure Q18–1). If Apaf1 and caspase-9 function in the same apoptotic pathway, how is it possible for these deficient
Answer Preview: The Case 9 -/- mutants show normal web-cell apoptosis as compared to the Apaf-1 -/- mutants because …

, Chapter: 4 -Problem: 4 >> In a comparison between the DNAs of related organisms such as humans and mice, identifying the conserved DNA sequences facilitates the search for functionally important regions. Is the statement true? Explain why or why not.
Answer Preview: True This is the concept of comparative genomics It is a field of biol…

, Chapter: 19 -Problem: 12 >> At body temperature, L-aspartate in proteins racemizes to D-aspartate at an appreciable rate. Most proteins in the body have a very low level of D-aspartate, if it can be detected at all. Elastin, however, has a fairly high level of D-aspartate. Moreover, the amount of D-aspartate increases in direct proportion to the age of the person from whom the sample was taken. Why do you suppose that most p
Answer Preview: The racemization of L-Asp to D-Asp is a really slow process, but the D-form to L-fo…

, Chapter: 20 -Problem: 6 >> Mortality due to lung cancer was followed in groups of males in the United Kingdom for 50 years. Figure Q20–1 shows the cumulative risk of dying from lung cancer as a function of age and smoking habits for four groups of males: those who never smoked, those who stopped at age 30, those who stopped at age 50, and those who continued to smoke. These data show clearly that individuals can substantial
Answer Preview: Lung cancer is the most common cancer-causing the death of a large number of men and women. And the common age group of lung cancer is six to seven de…

, Chapter: 23 -Problem: 7 >> Clostridium difficile infection is the leading cause of hospital-associated gastrointestinal illness. It is typically treated with a course of antibiotics, but the infection recurs in about 20% of cases. C. difficile infections are difficult to eradicate because the bacteria exist in two forms: a replicating, toxin-producing form and a spore form that is resistant to antibiotics. Fecal microbiota
Answer Preview: Fecal microbiota transplantation believed to be more ef…

, Chapter: 17 -Problem: 4 >> Chromosomes are positioned on the metaphase plate by equal and opposite forces that pull them toward the two poles of the spindle. Which statements are true? Explain why or why not.
Answer Preview: The statement is true that chromosomes are positioned on the metaphase plate by equal and opposite forces that pull them towards poles and pushes towards the equator. Mitosis is the process that parti…

, Chapter: 19 -Problem: 11 >> The glycosaminoglycan polysaccharide chains that are linked to specific core proteins to form the proteoglycan components of the extracellular space are highly negatively charged. How do you suppose these negatively charged polysaccharide chains help to establish a hydrated gel-like environment around the cell? How would the properties of these molecules differ if the polysaccharide chains were un
Answer Preview: The negatively charged carboxylate and sulfate groups on the proteoglycan bind positively charged i…

, Chapter: 21 -Problem: 16 >> The extracellular protein factor Decapentaplegic (Dpp) is critical for proper wing development in Drosophila (Figure Q21–3A). It is normally expressed in a narrow stripe in the middle of the wing, along the anterior–posterior boundary. Flies that are defective for Dpp form stunted “wings” (Figure Q21–3B). If an additional copy of the gene is placed under control of a promoter that is active in the
Answer Preview: DPP (Decapentaplegic) Is a morphogen that involved the development of Drosophila. DPP plays a ve…

, Chapter: 21 -Problem: 13 >> The mouse HoxA3 and HoxD3 genes are paralogs that occupy equivalent positions in their respective Hox gene clusters and share roughly 50% identity in their protein coding sequences. Mice with defects in HoxA3 have deficiencies in pharyngeal tissues, whereas mice with defects in HoxD3 have deficiencies in the axial skeleton, suggesting quite different functions for the paralogs. Thus, it came as a
Answer Preview: Genes having specificity, genes must be kept on the origina…