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AGR 3303 (3 credits) University of Florida - Fort Lauderdale  |
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| Below is exam #3 for 1993, Advanced genetics |
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AGR 3303 - Genetics 29 Nov 1993 University of Florida - Fort Lauderdale Exam #3: ADVANCED GENETICS Name ________________________________________
Multiple choice (30 pts) Read these carefully. One and only one response (a, b, c, d, or e) completely and correctly answers the question, or completes the statement. Circle the appropriate response; please make sure your circle is unambiguous. 1. A nucleotide substitution may have no effect on a structural gene because: a. there is no lower dosage for mutations b. the presence of base analogs c. the code is degenerate d. it would cause a frameshift e. it is masked by epistatic effects 2. Mutations are important in evolution because: a. they can lead to rapid replacement of normal alleles b. they provide the raw material for natural selection c. they are directional, that is, they occur as a result of natural selection d. all of the above e. none of the above 3. Heritability provides a measure of: a. environmental change b. the concordance of twins c. the number of genes determining a quantitative trait d. the genetic portion of the phenotypic expression of a trait e. all of the above 4. Pleiotropy is exemplified by: a. people with dark hair often have brown eyes; people with blond hair often have blue eyes b. the gene for hair color and the gene for eye color are linked on the same chromosome c. two genes interact epistatically to effect the same trait d. the DNA molecule cannot be opened without completely unravelling it e. some genes have partial penetrance 5. The physical appearance of an individual plant or animal is due to: a. its parents b. its environment c. its genotype d. its experience e. all of the above 6. Wheat is normally self-pollinated, thus most cultivars are "pure-lines" (a population of homozygous individuals). Below are the F2 results of the cross between a tall (80-cm) wheat cultivar and a short (40-cm) wheat cultivar. How many genes control height? Assume that each gene contributes equally to height.
a. 1 gene determines wheat height b. 2 genes determine wheat height c. 3 genes determine wheat height d. 4 genes determine wheat height e. 5 genes determine wheat height 7. For the example in problem #6, the distribution of heights of F1 plants would have been: a. similar to the F2 b. much narrower than the F2 c. much broader than the F2 d. two peaks, one similar to each parent e. cannot be determined 8. Which is an example of genotype X environment interaction? a. Native-born children in the United States are often taller than their immigrant parents. b. Alleles for coat color in mammals are expressed only at certain temperatures (e.g., rabbit with dark nose); depending on the presence or absence of an allele, and the presence or absence of a threshold temperature, there may or may not be pigment. c. The presence of rare recessives in the general population. d. Polygenic inheritance leads to continuous distributions. e. None of the above. 9. Inbreeding results in: a. increased heterozygosity b. expression of recessive alleles c. natural selection d. all of the above e. none of the above 10. What is a trait which is affected by one pair of alleles so that the phenotypes can be easily placed into discrete categories? a. quantitative b. continuous c. additive d. polygenic e. qualitative
Matching (20 pts.) In each of the following ten blank spaces, insert the correct word or phrase from the following list: DNA amplification mutation natural selection primer probe recombinant DNA restriction endonuclease reverse transcriptase sequencing variance 11. An enzyme that cleaves DNA at or near specific nucleotide sequences
________________________________________. 12. A radioactively labelled fragment of DNA used to detect a complementary sequence in a diagnostic sample.
________________________________________.
13. The result of the polymerase chain reaction:
_________________________________________. 14. An enzyme that makes DNA from an RNA template:
________________________________________. 15. Something which determines the nucleotide order in DNA:
________________________________________.
16. A short length of DNA or RNA needed to get DNA polymerase started:
________________________________________. 17. Something which can switch proto-oncogenes to a condition of uncontrolled growth (e.g., certain kinds of cancer):
________________________________________. 18. Differential reproduction due to differences (in fitness) among genotypes:
________________________________________. 19. DNA joined from different organisms:
________________________________________. 20. A predictable measure of dispersion:
________________________________________.
Short answer (20 pts.) 21. Name four assumptions underlying Hardy-Weinberg equilibrium. For each, explain in ten words or less how a violation of any one of these assumptions can lead to a shift in allelic frequencies.
22. Four people are shipwrecked on a deserted island, two men with blood genotype AA, a woman with the genotype AO, and a woman with the genotype OO. Assume that these people intermate and produce children, and that their children intermate and produce an F2 generation (grandchildren). What is the expected frequency of alleles, genotypes, and phenotypes among the F2's? Assume no selection, mutation, migration, or genetic drift. If the formula 1=p2 +2pq +q2 helps, use it. You may report fractions. List of alleles: Their respective frequencies:
List of genotypes: Their respective frequencies:
List of phenotypes: Their respective frequencies:
23. As a plant breeder you have described and released a new Aglaonema cultivar, 'Zebra Mist'. It is variegated (leaves are striped green and white) due to a dominant allele. While 'Zebra Mist' is heterozygous, the normal all-green cultivars are homozygous recessive. 'Zebra Mist' is propagated vegetatively through stem divisions, thus all commercial cuttings are supposed to be part of the same identical genetic clone as your original selection, hence always variegated. Unfortunately, buyers have complained that they have bought plants labelled as 'Zebra Mist' from your company, but they are all green. Explain in 75 words or less whether: a. the all-green plants are probably natural mutations, or b. the all-green plants are probably a contaminant cultivar which was introduced due to mislabelling, admixture, or other handling problems. For purposes of this exercise, you can present any kind of pretend evidence you want, provided it must come only from the plants themselves and your knowledge of genetics. (You cannot ask the packaging department if they fouled up the order). Make sure to mention the evidence that leads to your explanation (10 pts.) |
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