Chromosomes, Mapping, and Meiosis-Inheritance Connection

Which conclusion is a result of Thomas Hunt Morgan’s research with fruit flies?

• Chromosome assortment during meiosis is not random.

• Linked genes are located on the same chromosome.

• The physical distance between genes can be determined.

• Genes recombine independently during mitosis.

Which observation of Morgan’s is evidence that crossing over occurs?

• Linked genes are sometimes inherited separately.

• Some dominant traits are always inherited together.

• Inheritance of gene combinations is not random.

• Fruit flies have only two groups of linked traits.

Two genes on a given chromosome that are most likely to be inherited together are

• 6.8 map units apart.

• 10 map units apart.

• 2 map units apart.

• 18.5 map units apart

Suppose that the distance between two genes on a linkage map is 7 units. The cross-over frequency between the two genes is

• 0.7%

• 7%

• 70%

• 700%

Suppose the cross-over percentages for three gene pairs are: A to B = 9.5%, B to C = 14.5%, and A to C = 5%. Which of the following sequences could represent the order of these genes on a chromosome?

• CAB

• ABC

• CBA

• ACB