ZOOL/BOT 3333

The answers to the practice exam are found here, but please work the practice exam first!

A. True/False and multiple choice questions (2 points each). Please fill in your answers on the scantron sheets provided. For true/false questions, please indicate whether a statement is true (1) or false (2), or, for multiple choice questions, circle the letter representing the single best choice. If a question seems ambiguous to you, please raise your hand and I will try to clarify the source of ambiguity.

Questions 1-5 pertain to the following Mendelian crosses. In garden peas, tall vine (D) is dominant over dwarf (d), green pod color (Y) is dominant over yellow (y) and round seed (W) is dominant over wrinkled seeds (w).

1. True or false. All plants that have dwarf vines and produce yellow and wrinkled seeds would be expected to breed true for these traits if allowed to self-fertilize.
2. A tall plant of uncertain parentage is crossed to a short plant. The cross produces offspring with the following phenotypes: 35 short, 38 tall.
   The genotype of the tall plant for this trait was:
   a) DD; b) Dd; c) dd; d) either DD or Dd; e) can not be determined from the information given.
3. A tall, yellow, round plant crossed to a dwarf, green, round one produces offspring in the following ratios: 3/8 tall, green, round; 3/8 dwarf, green round; 1/8 tall, green, wrinkled; 1/8 dwarf, green, wrinkled. The genotypes of the two parent plants are:
   a) DDYYWW and DDYyww; b) DdyyWw and ddYYWw; c) DdyyWW and ddYyww; d) DdYyWw and DdYyWw; e) DDYYWW and ddyyww.
4. A tall, green round plant crossed with a tall, green, round plant produces offspring with the following phenotypes: 28 tall, green, round; 9 tall, yellow, round; 10 dwarf, green, round, 8 tall, green, wrinkled; 4 dwarf, yellow round; 4 tall, yellow, wrinkled; 3 dwarf, green, wrinkled. The genotypes of the two parent plants are:
   a) DDYYWW and DdYyWw; b) DDYYWw and DDYYWw; c) DdYyWw and DdYyWw; d) DdYyWW and DdYyWw; e) none of the above.
5. True or false. If the cross described in question 4 were repeated 10 times, we would never expect to see any dwarf, yellow, wrinked plants among the progeny.

Questions 6-9 pertain to a cell about to undergo meiosis that has a diploid chromosome number of 10.

6. How many pairs of homologous chromosomes are present in the nucleus of this cell?
   a) 2; b) 4; c) 5; d) 10; e) 20.
7. Assume that both members of one homologous pair carry the allele B. How many copies of B would exist in the nucleus during prophase I?
   a) 2; b) 4; c) 5; d) 10; e) 20.
8. How many total chromatids would be present during prophase I?
   a) 2; b) 4; c) 5; d) 10; e) 20.
9. In this cell, solely on the basis of random alignment of chromosomes during meiosis, the number of different chromosomal combinations that can be generated in the gametes is:
   a) 10; b) 20; c) 32; d) 1024; e) 1,240,000.
10. True or false. In human females, the onset of puberty indicates the beginning of the meiotic process of egg production.

For questions 11-12, consider the cross:

AaBBCcDdEe x aaBbCCDdEe

where all genes exhibit complete dominance and independent assortment.

11. What fraction of the offspring of the above cross would have a genotype similar to the first parent (i.e. AaBBCcDdEe)?
    a) 9/64; b) 9/32; c) 27/64; d) 9/256; e) none of the above.
12. What fraction of the offspring of the above cross would have a phenotype similar to the first parent?
    a) 9/64; b) 9/32; c) 1/4; d) 27/64; e) none of the above.
13. Flower color in snapdragons is a trait showing incomplete dominance. It is governed by two alleles, CR and CW, for red- and white-pigment production, respectively. If a pink-flowered plant is crossed to a white-flowered plant, then the ratio of progeny are expected to be:
    a) all pink; b) 9 red:6 pink:1 white; c) 1 pink:1 white; d) 1 red:1 white; e) 1 red:2 pink:1 white.

Questions 14-15 pertain to the following. On a particular day, five babies are scheduled to be born in the delivery area of a hospital.

14. What is the probability that 3 will be female and 2 will be male?
    a) 1/16; b) 1/8; c) 1/4; d) 5/16; e) 9/16.
15. What is the probability that at least 1 will be a female?
    a) 1/5; b) 3/8; c) 4/5; d) 17/16; e) 31/32.
16. True or false. For typical somatic cells undergoing cyclic divisions, interphase is usually the shortest phase of the cell cycle.
17. True or false. The wild-type allele is defined as the allele that is always dominant over a non-wild-type allele.
    
18. Manx cats have a tail-less phenotype. When Manx cats are mated with one another, the ratio of tail-less progeny to normal-tailed progeny is 2:1. These results suggest that the trait determining the tail-less condition:
    a) is recessive; b) is lethal in homozygotes; c) must be modified by the presence of other gene loci; d) all of the above; e) two of the above are correct.

Questions 19-20 pertain to the following pedigree, where two different genetic diseases are observed. In this pedigree, a cross represents the occurence of an extra finger and a black square represents the occurrence of an eye disease.

19. In the above pedigree, what is the most likely pattern of inheritance for the occurrence of an extra finger?
    a) autosomal dominant; b) autosomal recessive; c) X-linked dominant; d) X- linked recessive; e) Y-linked inheritance.
20. In the above pedigree, what is the most likely pattern of inheritance for the occurrence of eye disease?
    a) autosomal dominant; b) autosomal recessive; c) X-linked dominant; d) X- linked recessive; e) Y-linked inheritance.

B. Match and Identify (2 points each). Please match the following terms in part I with the appropriate definitions or specific examples given in part II. For each term, provide the single best answer; no term in part II should be used more than once. Please note that two circles must be filled for each answer.

part I.

• 41-2. X-linked recessive transmission
• 43-4. norm of reaction
• 45-6. consanguinity
• 47-8. heterogametic sex
• 49-50. Sutton/Boveri hypothesis
• 51-2. epigenesis
• 53-4. tetrad
• 55-6. holandric inheritance pattern
• 57-8. XXY karyotype
• 59-60. autosome

part II.

• aa) August Weismann
• bb) bivalent
• cc) inbreeding
• dd) transmission of the TDF gene in humans
• ee) chromosomal theory of inheritance
• ab) classical hemophilia
• ac) produces identical gametes relative to sex chromosomes
• ad) non-sex chromosome
• ae) phenotypic fluctuation of genotype relative to environment
• ba) consequence of nondisjunction
• bc) centromere
• bd) pangenesis
• be) replaced preformation theory
• ca) female birds or male fruit flys

C. Short Problems (15 points). Please answer the following problems. Be sure to show all work (eg. calculations); partial credit can only be assigned on the basis of work shown.

1. Infantile amaurotic idiocy is a serious mental defect occurring in individuals homozygous for a recessive gene, a. Two normal parents have a daughter with symptoms of this disease, and a normal son, Brad. Brad marries Janet, a normal woman, whose brother was also affected by this same disorder.

   Draw the pedigree.

   What is the probability that Brad is a carrier of the recessive gene?

   What is the probability that the first child born to Brad and Janet would be affected with the disorder?

2. (7 points) Suppose that within a particular geographic region, a population of screech owls were sampled and classified for sex and plumage color as follows: red males 35, red females, 70, gray males 50, gray females 45. Use the chi-square method to answer ONE of the following (either a or b):

   a) Does the sex ratio deviate significantly from 50:50? (7 points)

   b) Is color independent of sex in this sample? (7 points + 4 extra credit points)