Question

Haemophilia is caused by
A) Dominant sex-linked gene
B) Recessive sex-linked gene
C) Recessive autosomal gene
D) Dominant autosomal gene

Answer 1

Hemophilia is typically a genetic bleeding condition in which the blood does not clot properly. This can lead to accidental bleeding as well as bleeding after an accident or surgery.

Complete Answer:
- In genetics, dominant and recessive is the association between a pair of genes. The genes that come from the mother and the father could be the same or dissimilar. If they are distinct, the feature that occurs and the gene that guides it is said to be dominant. The gene for a condition or feature that does not exist is recessive.
- A recessive trait gene can never reveal its effect until it enters another recessive gene or a dominant gene. Haemophilia is a recessive sex-linked condition. These forms of defects arise more frequently in men than in women.
- A daughter gains an X chromosome from her mother and an X chromosome from her dad. Suppose her mother's X chromosome has a natural blood-clotting gene. Suppose her father's X chromosome has a haemophilia gene.
- The daughter would not have haemophilia because her mother's natural blood-clotting gene is dominant. It would not cause instructions from the haemophilia gene to be received. The daughter is considered a haemophilia carrier. She does have a gene on one of her X chromosomes, and she might pass it on to her children. The mother would be the one who passes the gene for haemophilia. It is merely by chance that the haemophilia gene is passed on to the infant with haemophilia.

The correct option is B, recessive sex-linked gene.

Note: The intensity of a person's haemophilia is determined by the volume of a component in the blood. The lower the component, the more likely it is that there will be bleeding that can lead to severe health issues.