Lecture 20

Question 1

What does it mean if a gene is sex-linked?

Answer 1

The gene is found on the sex chromosomes

Question 2

If a condition is found to be more common in males, what might that say about the gene’s location?

Answer 2

Most likely on X chromosome

Question 3

How many genes are there?

Answer 3

Roughly 20,000

Question 4

How do we determine order and location of genes?

Answer 4

Using recombination freqencies

Question 5

If the distance between the two genes is smaller, will it be more or less likely to form a chiasma between them?

Answer 5

Less likely

Question 6

Calculate the recombination frequency :
A species of flowering plant has a gene (purple) that determines flower colour, and another gene (tall) that
controls plant height. A scientist performs a test cross between two lines of this species: one heterozygous plant
line with purple flowers and tall stems; and the other line pure-bred with white flowers and short stems. The
progeny from this cross comprise: 345 purple-flowered tall plants; 340 white-flowered short plants; 255 whiteflowered tall plants; and 260 purple-flowered short plants.

Answer 6

0.429/42.9%