Question

n humans, colour blindness is due to an “X” linked recessive trait we shall represent with the symbols Xn. Females that carry a hidden recessive gene for colour blindness in the heterozygous condition are called “CARRIERS”

Show two different crosses that would result in possible colorblind daughters.

Answer 1

The first possible cross is between a color blind man and a color blind carrier woman.Therefore, the color blind chromosome will be shown as X^N in a man ,since they carries one X. The X will carry the color blind gene. A woman has two XX chromosomes she can be carrier or color blind. The Recessive trait in a woman will be XXⁿ. The following illustration shows the crossing between a color blind man and color blind carrier woman.

X^NY XⁿX

Results

X^NXⁿ- Color blind daughter

X^NX- daughter color blind gene carrier

The second possible cross is between a color blind husband and a color blind woman .In this case all the daughters will be color blind.