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12 Cards in this Set
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- Back
- 3rd side (hint)
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The observation that the sickle-cell gene exists in a larger percentage of the population than one would expect given the virulence of the disease can best be explained by the fact that:
a. homozygous recessives have the most fitness b. homozygous dominants have the most fitness c.heterozygotes have greater fitness than homozygous dominants d.all homozygous recessives fail to reach reproductive maturity |
The disease is lethal before adulthood, so there would be a strong selection pressure against homozygotes. Over time, this would tend to reduce the allele frequency in the population. For the allele to be carried by 40% of the population there must be a selection pressure in favor of the sickle-cell allele in the heterozygote. C is correct
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Aldosterone's mechanism of action on its target cell is most similar to that of which of the following hormones?
a. Testosterone b. Glucagon c. Insulin d.ACTH |
Two classes of hormones exist are steroid hormones and peptides. Included in steroid hormones are aldosterone and testosterone, which diffuse through the plasma membrane to bind to a receptor. Peptide hormones, including glucagon, insulin, and ACTH, cannot diffuse into the cell. Therefore, b, c and d are wrong.
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Aldosterone acts on proximal and distal tubules and collecting ducts of the nephron. Specifically, it binds to an intracellular receptor and promotes the transcription of the Na+/K+ ATPase gene, which reabsorbs Na+ and secretes K+, leading to more H2O reabsorption and higher blood pressure.
Activated aldosterone most directly regulates activity of which of the following enzymes? a. DNA polymerase b. RNA polymerase II c. Na+/K+ ATPase d. Renin |
b., because although it indirectly affects ATPase and Renin, it only directly affects mRNA production
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A diels-alder reaction formed two products: a cyclohexene with Ac0 and CN bound beta to double bond and a cyclobutane with an ethene that has AcO and CN alpha (20%). A scientist proposed a [4 +2} cycloaddition mechanism (A) and a two-step diradical process (B). The scientist observed the same products formed regardless of temperature or solvent and concluded Mechanism was B.
Was the scientist right? a. Yes, because the formation of two products implies a common transition state b. Yes because the rate of reaction is independent of a catalyst c. No because either reaction could for two products d.No, because the formation of two carbon radicals in a single molecule is impossible |
b, because either mechanism could make a cyclobutane
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Fluoroquinolones are a new class of antibiotics that are extremely effective against a wide range of bacteria. It has been determined that fluoroquinolones enter cells along with water via a passive transport mechanism. After exposing both bacterial and human cells to high concentrations of fluoroquinolones, a researcher discovered that, in the bacterial cells only, the DNA was nicked and supercoiling had been disrupted. Of the following, the most likely explanation ofor this is that floroquinolones:
a are unable to diffues into human cells b interfere with DNA polymerase, which is not in human cells c interfere with DNA gyrase, which is not in human cells d interfere with DNA helicase, which is not in human cells |
c, because they can enter all cells (they diffuse with water), a is wrong. Both euk and prok have DNA polymerase and helicase, but only prokaryotes use DNA gyrase to supercoil
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A tall plant with curly leaves (TT/CC) was crossed with a dwarf plant with straight leaves (tt/cc). Two fo the resulting F1s were crossed with each other and produced F2s as follows:
34 tall with curly 4 dwarf with straight 11 tall with straight 12 dwarf with curly Based on these results, are the genes for plant height and leaf shape linked? a. No, since recombination occurred b. No since the phenotype ratio is close to the expected ratio for this cross c.yes since recombination frequency is less than 50% d. Yes since there are considerably fewer recombinant plants than expected |
b, because the expected cross between unlinked genes in heterozygous is 9:3:3:1
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M6P receptors are good markers for a pathway that delibers lysozomal enzymes to lysosomal precursors known as endolysomes. Enzymes destined for the lumen of a lysosome are modified with M6P.
The M6P/M6P Receptor complex directs transport from golgi to an endolysosome, in manyt lysosomal storage diseases, one or more enzymes are not routed to the lysosomes. In inclusion cell disease (I-cell disease), a defect in the phosphorylation of mannose results in the secretion from the cell of all enzymes intended for the lysosome. A healthy celll, however, will only secrete 10% intended for lysosome. It has been discovered that kidney cells from a patient with I-cell disease can survive if placed in a medium with normal kidney cells. With is most likely to explain this recue of a lethally diseased cell? a Enzymes in the medium catalyze extracellular reaction s that usaully occur intracellularly b Genes for the normal enzyme are incorporated into the I-cell genome cM6P from the healthy cell gets converted to M6P receptor in the I-cell dM6P receptors on the I-cell surface can direct enzymes in the medium to the lysosomes |
d, because although the diseased cells will secrete enzymes into the media, the subrates will still be present within the cell in the lysosomes, so the defect will not be corrected this way. B is unlikely. There is no known mech. this way. C is not possible. D is best answer because there is only something wrong with the ability to tag proteins with M6P. There is no reason to believe that they lack the receptor for M6P ro the ability to transport proteins to the lysosome.
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PKU is an autosomal recessive disorder caused by a mutation in the enzyme that converts phenylalanine to tyrosine, preventing this reaction from occurring. The resulting excess phenyl-alanine is converted to phenylpyruvate, a phenylketone. Left untreated, PKU can lead to mental retardation. PKU is rare, occurring in 1 in 10,000 births. What is the approximate percentage of parents who are hetero zygous for the abnormal gene?
a 0.25% b 0.5% c 1% d 2% |
d. Remember the equation for genotype frequency: p^2 to 2pq + q^2 = 1. If disease is caused by recessive (q) and 1/10,000 is affected then q^2 = 1/10,000. so q = 1/100. Then p = 99/100. 2pq is number heterozygotes
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Structural isomers have the same molecular formula, but different connectivities. Choices A, B and C can be eliminated since they all imply identical atom connectivity
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Since an alkene is formed the conversion is an elimination
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The 1H NMR Spectrum of Pyruvate would contain one resonance composed of a
a singlet b doublet c triplet d quadruplet |
proton-proton splitting occurs when nonequivalent H's are bonded to neighboring atoms. Since this molecule has only one kind of equivalent H, it will not experience any splitting. So A is the answer.
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pyruvate's only H's are in a methyl group
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