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AGR 3303 (3 credits) University of Florida - Fort Lauderdale  |
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| Below is exam #1 for 1994, Mendelian genetics |
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AGR 3303 - Genetics 26 Sep 1994 University of Florida - Fort Lauderdale Exam #1: PARTICULATE GENETICS Multiple choice. (60 pts.) Please 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 and turn in this exam. Make sure your circle is unambiguous. Take time to relax. (Suggestion: put the problem into gene symbols, if that helps you to visualize the problem and its solution.) 1. The alleles determining human ABO blood types are an example of: a. dominance/recessiveness b. codominance c. multiple alleles d. all of the above e. none of the above 2. What single information would most help in predicting genotypic frequencies of the progeny resulting from a cross? a. the allelic relationship, i.e. dominance, incomplete dominance, codominance b. the frequency of the various possible parental phenotypes c. the frequency of the various possible gametes d. the number of chromosomes e. whether sex linkage was involved 3. Duchenne muscular dystrophy in humans is a rare, sex-linked, recessive trait. A man has two biological sons, #1 and #2. The sons have different mothers. Son #1 has Duchenne muscular dystrophy. Which value most closely estimates the chance that son #2 has the same condition? a. 100% b. 50% c. 25% d. 0% e. cannot be determined unless the father's phenotype is known 4. In the following metabolic pathway for anthocyanin (purple coloration) the enzymes C and D are coded for by the dominant alleles at the gene loci C and D, respectively. The C and D loci are not linked, but assort independently. What would be the frequency of green (purple deficient) progeny from the cross ccDd X CCdd ? enzyme C enzyme D anthocyanin precursor (green) > anthocyanin intermediate (green) > anthocyanin (purple) a. 100% b. 50% c. 25% d. 12.5% e. 0% 5. A chi-square value was calculated from a genetics experiment, based on a comparison of observed phenotypes with their expected distribution based on Mendelian genetics. The tabular probability level for chi-square was P = 0.90, thus we: a. reject the null hypothesis b. accept the null hypothesis c. cannot conclude anything because we do not know the null hypothesis d. cannot conclude anything because we do not know the chi-square value e. cannot conclude anything because we do not know alternative hypotheses(is) 6. Polyploidy a. is common among animal species, such as humans. b. involves the lack of a nucleus. c. is important in horticultural plants. d. is noted in humans with the XYY chromosome configuration. e. was discovered by Mendel. 7. Color of chickens is determined by interacting loci: AA or Aa give white, aaBB or aaBb give colored, and aabb produces white. What are the phenotypic frequencies of the offspring from a cross between two fully heterozygous plants a. 15 white : 1 colored b. 13 white : 3 colored c. 12 white : 4 colored d. 9 white : 7 colored e. none of the above 8. Which relationship is correct? a. the gamete is haploid, the zygote is diploid b. the gamete is diploid, the zygote is haploid c. the gamete and the zygote are diploid d. the gamete and the zygote are haploid e. none of the above 9. A maternity case involves an infant with type A blood. Who could or could not be the genetic mother? a. a woman with type A blood could not be the mother b. a woman with type AB blood could not be the mother c. a woman with type O blood could not be the mother d. a woman with type B blood could not be the mother e. all of the above could be the mother 10. Which statement is false? a. Heritability is the ratio of genotypic variance divided by phenotypic variance. b. Plant breeders would prefer that heritability be high. c. Identical twins provide a measure of environmental variance. d. The variance of identical twins is zero. e. Heritability is determined from the chi-square table. 11. Alternative forms of a single gene are: a. chromosomes b. alleles c. loci d. polygenes e. all of the above 12. In Drosophila, all members of a strain of flies express a jagged wing margin due to a sex-linked mutation. What evidence determines if the mutation is recessive or dominant? (Suggestion: this is more difficult than it sounds, thus you should carefully write down the parental genotypes for the two possible crosses, using appropriate gene symbols to indicate dominance or recessiveness, as the case may be. Look at the consequences.) a. cross a mutant female to a normal male; if the sexes differ in the trait, then the mutation must be recessive b. cross a mutant female to a normal male; if the sexes are the same in the trait, then the mutation must be recessive c. cross a mutant male to a normal female; if the sexes differ in the trait, then the mutation must be dominant d. all of the above e. none of the above 13. A chi-square was calculated from a genetics experiment, based on a comparison of observed fruit fly phenotypes with their expected distribution based on a Mendelian model. The tabular probability level for chi-square was P < 0.00001, thus we conclude that: a. the null hypothesis is accepted b. the genetic model does not adequately explain the results c. the experiment was a success d. all of the above e. none of the above 14. If an organism has 2n=8, then a. during mitosis there will be 4 chromosomes going to each pole b. during meiosis there will be 8 chromosomes going to each pole c. the individual is an octoploid d. during meiosis, there will be 8 pairs of chromosomes e. during meiosis, there will be 4 pairs of chromosomes 15. A man died from Huntington's disease, which is caused by a dominant, autosomal allele. What is the probability that his grandson will have the disease? a. 0% b. 25% c. 50% d. 75% e. 100% 16. What is true of sex-linked traits in humans? a The man always receives his X chromosome from his father. b. The man can receive his X chromosome from his father's mother. c. The man can receive his X chromosome from his mother's father. d. Males can be unaffected carriers of the trait. e. The traits are expressed only when they are determined by recessive alleles. 17. Coat color of horses can be cremello (almost white), palomino (golden coat with lighter mane and tail), or chestnut (brown). Among these phenotypes, palomino never breed true. Cremello and chestnut always breed true when they are mated with other horses of the same coat color. What is the simplest explanation for these relationships? a. multiple alleles b. epistasis c. incomplete dominance d. inactivation of the X-chromosome e. none of the above could explain the observations 18. Genetic crossing over is important in genetics because: a. it is a means by which new gene combinations are created b. it provides an estimate linkage distances c. it is consistent with the idea that genes are carried on chromosomes d. all of the above. e. none of the above. 19. Consider three genes, each with two alleles. In a diploid organism, how many possible genotypes are there? a. 6 b. 8 c. 9 d. 16 e. 27 20. Assume that each of three genes determines a different trait, and each gene has two alleles, one of which is dominant, and the other recessive. In a diploid organism, how many possible phenotypes are there? a. 6 b. 8 c. 9 d. 16 e. 27
Matching (21 pts.) In each of the following twenty-one blank spaces, insert the correct word or phrase from the list at the bottom of the page. 21. A stage of meiosis when the paired chromosomes are lined up and are ready to disjoin __________________________________. 22. Homologous ("similar") chromosomes do this, only in meiosis.
__________________________________. 23. A form of a gene; new forms arise through mutation.
__________________________________. 24. The particle which determines a character in Mendelian genetics.
__________________________________.
25. In human blood types the alleles coding for the A antigen and the B antigen are related by
__________________________________. 26. All the genes of an organism; also, the allelic condition for a particular gene or genes.
__________________________________. 27. A chromosome variation involving three complete sets of chromosomes; often results in sterility.
__________________________________. 28. The diploid cell from the union of two haploid gametes.
__________________________________. 29. An organelle of eukaryotes which is involved with respiration
__________________________________. 30. A condition giving rise to progeny ratios which would not be predicted on the Mendelian principle of independent assortment of genes during meiosis.
__________________________________.
31. Organisms which lack a nucleus
__________________________________. 32. Alleles which are expressed only when they occur in the homozygous condition __________________________________. 33. One of Mendel's four postulates of inheritance.
__________________________________ 34. A good measure of central tendency
__________________________________. 35. There is one of these for each chromosome
__________________________________. 36. A genetic interaction or nonreciprocal masking. For example, the Bombay allele in humans (hh) always leads to type O blood, regardless of the presence of an A or a B allele.
__________________________________.
37. A type of cell division which leads, ultimately, to new genetic combinations
__________________________________. 38. An individual having three or more complete sets of chromosomes is
__________________________________. 39. A continuous range of phenotypic expression may derive from this type of inheritance
__________________________________. 40. Down syndrome in humans is caused by
__________________________________. 41. A good measure of dispersion
__________________________________.
Short answer 42. What are four characteristics of the genetic material? (4 pts.)
43. What concept was lacking in the theory of natural selection, at (4 pts.) the time Darwin proposed it? Explain briefly why it is critical to the theory.
44. A homozygous dominant plant (genotype AABB) is crossed with a (4 pts.) homozygous recessive plant (genotype aabb). Their F1 hybrid is backcrossed to the homozygous recessive plant. What is the expected frequency (%) of the four possible progeny genotypes, under the following conditions:
45. A plant with the genotype AaBb is self-pollinated. Genes A and B are epistatic, that is, only A_B_ plants are green, while other combinations are variegated. There is no linkage. Using Punnett's square, show what is the ratio of green to variegated in the progeny. Make sure to show your work in detail. (7 pts)
The expected ratio is __________ green : __________ variegated |
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