Mendelian genetics II

Question 1

How many genes is phenotype determined by?

Answer 1

Interaction of many genes.
The more genes that interact, the more complex the inheritance.

Question 2

What are the two effects of genes?

Answer 2

Additive or epistatic.

Question 3

What is pleiotropy?

Answer 3

One gene controls multiple phenotypes so they do not segregate indepedently.

Question 4

What is linkage?

Answer 4

Tendency of genes that are located near to each other on a chromosome to be inherited together during meiosis.

Question 5

If two genes are close together, then how strong will the link be between their alleles?

Answer 5

Strongly linked so tend to be inherited together.

Question 6

If two genes are a long way apart, then their allelles will be ________ and show random __:__ inheritance(mendelian independent assortment)

Answer 6

unlinked
50:50

Question 7

What is the recombination fraction?

Answer 7

Proportion of offspring whcih are recombinant

100%x no. of recombinants divided by no. of offspring.

**max of 50%.

Question 8

What is genetic distance measured in?

Answer 8

cM(centi Morgans)
(Thomas Hunt Morgan)

1cM=1% offspring with recombinant phenotypes.

Question 9

What is the easiest method to map genes?

Answer 9

Three point test cross

Allows all distances to be calculated for mapping.

Question 10

What happens in the three point test cross.

Answer 10

In meiosis you have made copies of the chromosomes and so result with 4 copies.

Question 11

What are the 4 outcomes of a three point testcross?

Answer 11

1) No recombination in either interval (most likely)

2) Recombination in first interval only (aBC and Abc)

3) Recombination in second interval only (ABc and abC)

4) Recombination in both intervals (AbC and aBc) (least likely)