Lecture 17: X-inactivation

Question 1

Which chromosome is smaller and has fewer genes

Answer 1

Y chromosome

Question 2

What is the Lyon Hypothesis

Answer 2

One X chromosome in female XX cells ins largely inactivated.

In early development random X is inactivated

Question 3

What are autosomes

Answer 3

Autosomes (chromosomes 1-22) are present in equal numbers in
both male and female cells.

(sex chromosomes are present in unequal numbers in m/f)

Question 4

What does X inactivation cause

Answer 4

Balances the doses of X chromosome gene expression in females and males

Question 5

What are Barr Bodies

Answer 5

Inactivated X’s. They condense into Barr Bodies

Highly condensed structure that lies against the nuclear envelope in cells of females but not males

Question 6

What gender are all calico cats and how do you know

Answer 6

Female. Random inactivation of X
chromosomes leads to mosaic
patterning.

Question 7

Many genetic diseases map to the X
chromosome. These are often more common in…

Answer 7

Males