Question

1)Suppose that in Mendel’s pea plants, you are studying two genes, C and D, located close together on the same chromosome. You cross together a CCDD plant with a ccdd plant. The F1 plants have the genotype CcDd. This plant will make four gamete types, but most of them will be CD and cd types. Why will it not make similar numbers of the four gamete types? What is the mechanism that produces cD and Cd gametes?

Answer 1

It will not make similar numbers of four gametes because genes that are very close to one another on the same chromosome can be linked,ie they tend to remain together.This is a case of exception from mendels law of independent assortment.Here each parent plant can produce only one type of gamete.

The mechanism that produces cD and Cd gametes is a DIHYBRID CROSS which follows LAW OF INDEPENDENT ASSORTMENT.Here the parent plant in the second F2 generation can produce four types of gametes in equal proportions.This law implies that alleles for different traits are sorted into gametes independently of one another.