Determine if the statement is true or False and why it is tr

Determine if the statement is true or False and why it is true/false

1. A pure line plant of genotype A/A . b/b is crossed to another pure line plant a/a . B/B. The F1 hybrid is testcrossed. If both genes are unlinked, the double homozygous recessive individuals in the progeny of the testcross will be about 25%

2. A pure line plant of genotype A/A . b/b is crossed to another pure line plant a/a . B/B. The F1 hybrid is

testcrossed. If both genes are closely linked with nearly no crossover, the double homozygous recessive

individuals in the offspring of the testcross will be about 25%.

3. In a diploid plant, genes A and B are closely linked. Single crossovers between these two genes occurs

only in 10% of meiosis. Multiple crossovers are never observed. If an individual is heterozygous for both

genes, then approximately 10% of its gametes are expected to be recombinant type.

Solution

Answer:

1). True

AAbb x aaBB--Parents

AaBb ---F1

AaBb x aabb---Test cross

ab

AB

AaBb 25%

Ab

Aabb 25%

aB

aaBb 25%

ab

Aabb 25%

2). False

AAbb x aaBB--Parents

AaBb ---F1

AaBb x aabb---Test cross

As there is no crossovers, double heterozygote produces only AB &ab gametes.

ab

AB

AaBb 50%

ab

Aabb 50%

3). True

% of crossover = % of recombinants

AaBb produces 90% parental combination of gametes (AB- 45% & ab-45%) and 10% recombinant type (Ab-5% & aB-5%)