HMB265H1 Chapter Notes - Chapter 1: Pleiotropy, Wild Type

In need of assistance. Please help answer the following.

1) Pure-breeding yellow guinea pigs crossedwith pure-breeding white guinea pigs produce only cream-coloredoffspring. This pattern indicates incomplete dominance. Rough hairis found to be dominant to smooth hair. Give the F1 and F2genotypic and phenotypic ratios of a cross of a smooth white guineapig with a homozygous rough yellow guinea pig.

2) A breeder of cattle has a herd of white cowsand a roan bull. Hair color in this breed is controlled by anincomplete dominant gene. The two homozygous forms are either redor white, and the heterozygous is roan. Answer the followingquestions please

What color calves are expected and in whatproportion?

Outline a procedure to develop an all-redherd.

3) In horses, black coat color is influenced bythe dominant allele (B), and chestnut coat color is influenced bythe recessive allele (b). Trotting gait is due to a dominant gene(T), pacing gait to the recessive allele (t). If a homozygous blacktrotter is crossed with a chestnut pacer:

What will be the appearance of the F1 and F2generations?

Which phenotype will be the most common?

Which genotype will be the most common?

Which of the potential offspring will be certain tobreed true?

4) In garden peas, one pair of alleles controlsthe height of the plant and a second pair of alleles controlsflower color. The allele for tall (D) is dominant to the allele fordwarf (d), and the allele for purple (P) is dominant for the allelefor white (p). A tall purple crossed with a tall purple produces ¾tall purple and ¼ tall white. What is the genotype of the parents?

5) Three alleles control the ABO blood types.I^A and I^B are codominant genes, so thecombination of I^AI^B produces the AB bloodtype. The third allele I^ois recessive to the other twoalleles. Indicate which of these parents could produce the givenchild and submit your response to the instructor.

A X AB produce B child.

A X O produce A child.

A X B produce O child.

A X AB produce O child.

A X AB produce B child.

B X B produce O child.

AB X AB produce A child.

11. You suspect that two genes interact with one another to determine the product of a pathway you are studying. You cross two pure breeding plants—one with white flowers and one with pink—to make F1 individuals that have blue flowers. You cross the F1 generation and observe the following numbers of individuals with different phenotypes: Number of individuals Phenotype 91 Blue 30 Pink 39 White Which pathway best explains these results? (Note that arrows indicate enzymatic reactions carried out by products of genes 1 and 2. Assume that buildup of metabolites will determine flower color.)

Question 12 and 13: Consider the biochemical pathway presented below. This pathway determines pigment production in pea flowers. (Note: gene products are required for each reaction to proceed.)

12. Do you expect that genes A and B will interact with one another?

A. Yes B. No C. Insufficient information to determine

13. What phenotype ratio would you expect in offspring produced by crossing AaBb parents?

A. 9:3:3:1 (blue : green : yellow : white) B. 9:3:4 (blue : green : white) C. 9:7 (blue : white) D. 15:1 (blue : white)

14. How can haplosufficiency explain dominance of an allele that codes for a functional protein over a null (loss of function) allele?

A) a single functional copy of the gene produces sufficient gene product for normal biological function B) a single functional copy of the gene produces insufficient gene product for normal biological function C) the null allele produces a product that interferes with proper function of the normal allele D) the null allele produces a product that does not interfere with proper function of the normal allele E) the null allele rapidly mutates to reacquire normal functionality

15. In a plant species with genes A and B, you have isolated recessive mutant alleles at each locus, which you call a and b. You would like to know whether these two genes are linked. To test this hypothesis, you obtain an individual that is heterozygous at both genes (AB/ab) and perform a test cross. Which results would be most consistent with these loci being tightly linked? (Results are counts of the numbers of offspring from the testcross.)

A. Ab/ab 390 aB/ab 410 AB/ab 350 ab/ab 420

B. Ab/ab 80 aB/ab 73 AB/ab 760 ab/ab 754

C. Ab/ab 700 aB/ab 695 AB/ab 56 ab/ab 59

D. Ab/ab 400 aB/ab 65 AB/ab 50 ab/ab 659