Solutions For An Introduction to Genetic Analysis Chapter 17 Problem 70P

The above table can also be written as:

The species G. hirsutum has twice the number of chromosomes of the other species. Since these species form bivalent pairs in the hybrids, the karyotype of G. hirsutum must consist of chromosomes of two species. Hence, this species G. hirsutum must have one large and one small set of chromosomes.

In the first hybrid, the genome of G. hirsutum consists of one small set of chromosomes.

In the second hybrid, the genome of G. hirsutum consists of one large set of chromosomes.

In the third hybrid, we see the confirmation of the conclusion of the first two hybrids.

Hence, the original parents must have had the following constitution:

• G. hirsutum 26 large and 26 small

• G. thurberi 26 small

• G. herbaceum 26 large

The phylogenetic relationship can be shown in the following diagram:

The species G. hirsutum is a polyploid derivative of a cross between the two Old World species. This can be easily checked out by looking at the chromosomes.