Question

Which one is a sex-linked disease?
1. Albinism
2. Beriberi
3. Colour blindness
4. Tylosis

Answer 1

Correct Answer - Option 3 : Colour blindness

Concept-

• The sex-linked disease is the transmission of characters and their determining genes along with sex-determining genes.
• Sex-determining genes are borne on the sex chromosomes and, therefore, are inherited together from one generation to the next.
• Most sex-linked genes are located on the X-chromosome, forming X-linkage.
• Two important sex-linked human diseases are hemophilia and color blindness.

Explanation- 

• Colour blindness condition is usually passed down from the parents' side which is a common hereditary condition.
• A man having color blindness can’t receive a color-blind ‘gene’ from his father, even if his father is color blind because his father can only pass an X chromosome to his daughters.
• A daughter with color blindness, therefore, must have a father who is color blind and a mother who is a carrier (who has also passed the faulty ‘gene’ to her daughter).
• If her father is not color blind, a ‘carrier’ daughter won’t be color blind.
• A daughter can become a carrier in one of two ways – she can acquire the ‘gene’ from a carrier mother or from a color-blind father.

Thereby color blindness is a sex-linked disease.

 

Albinism-

• Albinism is inherited as an autosomal recessive.
• Albinism is a condition, which is genetically inherited and marks the deficiency of pigmentation in eyes, hair, and skin.

Tylosis-

• The persons with tylosis have excessively thick skin on their palms.

Beriberi-

• Beriberi is caused due to deficiency of vitamin B₁.
• This is also known as thiamine deficiency.