Question

Patrick was hired by Dr. Ryan to work on a maize genome project. His research assignment was to map three linked genes which can cause brown midrib (bm), virescent seedling (v) and purple aleurone (pr) phenotypes respectively in maize. All the above mentioned alleles are recessive ones compared with the dominant wild type phenotype (designated with +).

Dr. Ryan gave Patrick a triple heterozygote strain which has both the recessive mutant and dominant wild type alleles. Patrick was asked to testcross the strain and collect the data from the progeny. Here is the data Patrick obtained after one year’s hard work in the field. Based on the phenotype, they are categorized into eight groups in the following talble (1-8 below). Please answer the Multiple Answer Questions below.

Phenotypes Number of Progeny Percentage

(1) brown midrib 710

(2) virescent seedling, purple aleurone 698

(3) Wild type 170

(4) brown midrib, virescent seedling purple aleurone 150

(5) virescent seedling 42

(6) brown midrib, purple aleurone 38

(7) purple aleurone 5

(8) brown midrib, virescent seedling 3

Question #7: Which progeny phenotype in the above table results from the double-crossover gametes?

a.

1

b.

2

c.

3

d.

4

e.

5

f.

6

g.

7

h.

8

Answer 1

Phenotypes Number of Progeny Percentage brown midrib 710 Parental Highest (2) virescent seedling, purple aleurone 698 -- Parental number Wild type 170 Single crossover (4) brown midrib, virescent seedling purple aleurone 150 -> Single crossover Single crossover Single crossover >Double crossover >Double crossover virescent seedling 42 (6) brown midrib, purple aleurone 38 purple aleurone number (8) brown midrib, virescent seeding Question #6: Which progeny phenotype in the above table results from the single-crossover gametes? b. d.