NAME: _____________________________________ STUDENT ID #: ______________________________ Page 1 of 8. Very short answer questions (one-sentence answers, please) – 3 points each. 4. Both the lac operon in E. coli and the GAL genes in budding yeast require that glucose be absent from the medium to achieve full activity. What is the biological rationale behind a phenomenon in which glucose regulates expression of a set of genes for the metabolism of some other sugar? 5. Leslie Orgel showed that the “constitutive synthesis” phenotype of certain lacI- strains can be diminished via the use of amber suppressors. What did that prove? 6. Yasuji Oshima used a yeast strain carrying a ts – temperature-sensitive – allele of GAL4 to show that Gal4p is synthesized constitutively. For purposes of this experiment, was exactly is sensitive to temperature in his gal4-ts strain? (please note that “Gal4” is an insufficiently eloquent answer) 7. Vernon Ingram did tryptic digests on normal and sickle hemoglobin and compared the patterns. The result was instrumental in the development of the “central dogma of molecular biology.” Why? 8. The large amount of repetitive DNA in the human genome is thought to be a consequence of one particular aspect of human biology. What is that aspect?NAME: _____________________________________ STUDENT ID #: ______________________________ Page 2 of 8. 9. Steve Jacobsen showed that clark kent and superman are alleles of the same gene, and that kryptonite controls the transition between clark kent and superman. The product of the kryptonite gene is related in a very interesting way to the fruit fly and human Su(var)3-9 gene. What is that relationship? 10. The INK4A locus in the human genome produces two small proteins that control function by Rb and p53. What phenomenon disables INK4A in human cancer without altering the primary DNA sequence of that locus? 11. In population genetics, changes in allele frequency are thought to underlie the phenomenon of biological evolution. Early on, one particular process was erroneously thought to be sufficient to evoke such changes. This was quickly disproven (by a mathematician and not a biologist), and two other major processes are now known to change alelle frequency. List all three processes, please. 12. M.C. King and colleagues showed that women who carry germline mutations in BRCA1 or BRCA2 have an ~80% lifetime chance of developing breast cancer. This predisposition, however, is markedly lowered in women who were not obese as adolescents, and who were also physically active at that time. This is an example of what geneticists call “norm of reaction.” Reaction of what to what? 13. In class, we discussed a Seattle family that thinks they carry “an enterpreneurial gene.” They are under this impression because members of multiple generations in this family have started their own businesses. Assuming “the tendency to start your own business” is a quantitative trait that is controlled by multiple loci, explain to these people, why Mendel’s second law makes it quite unlikely that “enterpreneurship” will be passed from a grandparent to a grandchild. Please limit your answer to two sentences – thank you!NAME: _____________________________________ STUDENT ID #: ______________________________ Page 3 of 8. Very short essay questions Question 13 (30 points). The diagram to the right shows data from the famous “PaJaMo” experiment. In fact, this is only half the data. Arthur Pardee did yet another cross, and data from that experiment yielded the famous Jacob-Monod model of lac regulation. What was that other cross? Please use formal genetic notation. _______________________________________ As you know, the success of this experiment was unequivocally predicated on the fact that no cytoplasm is transferred from donor to recipient during bacterial conjugation. How would the result of the experiment shown on the right be different if cytoplasm was in fact transferred during mating? Please draw those “data” in the box below (you don’t have to use French in your drawing if you do not want to). A key tenet of the model proposed by Jacob and Monod is action by a soluble repressor. Name the genetic test they used to prove the existence of such a repressor: ___________________________________NAME: _____________________________________ STUDENT ID #: ______________________________ Page 4 of 8. Question 14 (15 points) The diagram to the right shows a schematic of a screen performed by Berkeley’s own Jasper Rine in his efforts to identify loci involved in the silencing of budding yeast mating type loci. One critical aspect of the experimental setup here ensured its success, i.e., Prof. Rine’s isolation of mutants in the silencing process per se, rather than some other biological process relevant to yeast mating. What is that aspect? _________________________________ _________________________________ Shortly after Prof. Rine’s experiments identified the SIR genes, Michael Grunstein’s lab showed that yeast carrying a point mutation in the histone H4 tail fail to silence their mating type loci, and, furthermore, that a particular allele of SIR3 can suppress the silencing defect of these strains. What conclusion was drawn from that experiment? ______________________________________________________________________________ As we discussed in class, the silencing of yeast mating type loci, and the silencing of genes translocated into fly heterochromatin by position effect variegation are analogous (i.e., they use different molecular components, but the overall mechanisms are related). There are several analogous steps in the two processes. List one: ______________________________________________________________________________ mate to a cellsmate to a cellsNAME: _____________________________________ STUDENT ID #: ______________________________ Page 5 of 8. Question 15 (15 points) As you know, “positional cloning” of human disease genes involves, essentially, three steps. The first is “mapping by linkage” in a pedigree such as one shown to the right. Linkage of what to what? _____________________________________ _____________________________________ Once that is complete, scientists start “jumping and walking.” From where to where? ________________________________________ Finally, scientists need to prove that the gene
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