Top 5 Cases on Colour Blindness in Humans

The following points highlight the top five cases on colour blindness in humans.

Case # 1. Of what type will be the children with reference to colour blindness, when a man is colour-blind and his wife is normal?

Solution:

The cause of the colour blindness is the presence of recessive (c) gene on the X chromosome.

Because man is colour-blind (Xc Y) and his wife is normal (XX), following will be the results while cross­ing:

Following will be the results after fertilization:

(i) XXC, i.e., normal but carrier daughter.

(ii) XY, i.e., normal son.

Results:

No child will be colour-blind.

Case # 2. When a haemophilic male is mated with a heterozygous haemopbilic female, what haemophilic proportion will be resulted in each sex?

Solution:

Haemophilia is a disease that causes delayed clotting of blood. It is due to a recessive gene ‘h’, located on X chromosome.

Haemophilic gene is represented by ‘h’

Haemophilic male = XhY

Heterozygous haemophilic female = XhX

Results:

One haemophilic daughter

One carrier daughter

One haemophilic son

One normal son.

Case # 3. When a haemophilic male is mated with a ho­mozygous non-haemophilic female-What will be the result?

Solution:

Haemophilic male = XhY

Homozygous non-haemophilic female = XX

Result:

A ratio of 2 (carrier daughter) and 2 (Normal son) will be produced.

Case # 4. Of what type will he the children with reference to colour blindness, when a woman is colour-blind and her husband is normal?

Solution:

Colour-blind woman = XCX

Normal man = XY

Result:

In such a case one normal and one colour-blind son, and one normal and one carrier daugh­ter would be resulted.

Case # 5. When both the parents are colour-blind, can they produce a normal daughter?

Solution:

Results:

The above results indicate that the colour-blind gene (c) is passed to both the X chromosomes of the daughter and so no normal daughter can be produced.