Gene Linkage

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

If the distance between A/B is 0.12 mu and gene C is on the opposite side of A with respect to B at a distance of 0.23 mu, Which is the central gene in this map

• B

• A

• C

• Data insufficient

If the distance between A/B is 0.12 mu and gene C is on the opposite side of A with respect to B at a distance of 0.23 mu, What is the order of the gene linkage map

• both A - B - C and C - B - A are possible

• A - B – C

• C - A – B

• The linkage map cannot be detemined as the ratio is not 1:1

This is the reason why Mendel did not recognize linkage phenomenon in his experiments

• He studied only pure characters

• He did not have a powerful microscope

• The characters he studied were present on different chromosomes

• The characters he studied did show linkage but he missed it

1 map unit is equal to:

• 1 mutation

• 1 chromosome

• 1 nm

• 1% recombination

Causes genes to not segregate independently. Causes genes to be more likely to be inherited together. Represents an exception to Mendel's Law of Independent assortment.

• Epistasis

• Gene linkage

• Codominance

• Polygenic traits