Dosage Compensation by Sohail Jamil Qureshi

Each cell in your body contains .............. pairs of chromosomes.

• 23

• 22

• 21

• 20

One pair, the ..................................., determines gender. The

• sex chromosomes

• Autosome

Because females have

two X chromosomes and males have only one, body cells

randomly turn off one of the X chromosomes. This is called

...........................................................

• dosage compensation or X-inactivation.

• Incomplete dominance

Black patches are formed when an

X chromosome carrying the allele for orange coat color

is turned off.

• yes

• no

Orange patches are formed

when an X chromosome carrying the allele for black coat

color is turned off.

• yes

• no

Canadian scientist Murray Barr fi rst observed inactivated

X chromosomes, now known as ....................

• Barr bodies.

• Incomplete dominance

Barr bodies

appear as dark objects in the cell nuclei of female mammals.

• yes

• no