Question

5. What gametes are produced by the following organisms: a. Genotype YyRr, if Y and R are on different chromosomes b. Genotype YyRr, if dominant Y and R are on the same chromosome, no crossing over c. Genotype YyRr, if dominant Y and recessive r are on the same chromosome, no crossing over d. Genotype YyRr, if dominant Y and R are on the same chromosome, 50% crossing over

Answer 1

Answer:

a) YR, Yr, yR, yr

b) YR, yr

c) Yr, yR

d) YR, yr, Yr, yR

Explanation:  

Before gametes are formed, during anaphase sister chromatids separate and migrate to the poles. Following the low of segregation and independent assortment, alleles from the same trait and from different traits separate independently from each other. During this separation, there might be different gene combinations according to their position in the chromosome, the occurrence of crossing over, and the destiny of each chromatid.

a. Genotype YyRr, if Y and R are on different chromosomes

Genes are located in two different chromosomes, which means that there might be four possible gametes.

1. YR,
2. Yr,
3. yR,
4. yr

b. Genotype YyRr, if dominant Y and R are on the same chromosome, no crossing over

Genes are located in the same chromosome, which means that there might be two possible gametes.

1. YR
2. yr

c. Genotype YyRr, if dominant Y and recessive r are on the same chromosome, no crossing over

Genes are located in the same chromosome, which means that there might be two possible gametes.

1. Yr
2. yR

d. Genotype YyRr, if dominant Y and R are on the same chromosome, 50% crossing over

The fact that there is 50% crossing over means that these genes are not linked. There are four possible gametes

1. YR (parental)
2. yr (parental)
3. Yr (recombinant)  
4. yR (recombinant)