Question

Haemophilia is mentioned as trait carried by the mother and passed to her sons. What is the pattern of inheritance for this trait?
(A) Haemophilia is an allele carried on one of the mother’s autosomal chromosomes.
(B) Haemphilia is an allele carried on the Y chromosome because more males have this genetic disorder than females.
(C) Haemophilia is an allele carried on the X chromosome and can be directly inherited by the son from the father or the mother.
(D) Haemophilia is carried on the X chromosome and can only be inherited by the son if the mother is a carrier.

Answer 1

Hint: Haemophilia is an X-linked recessive disorder that is it is expressed in females only when both the alleles of haemophilia are present and is expressed in males even if X chromosome out of XY has haemophilic allele. So, the chances of males suffering from haemophilia is much more than females.

Complete Step by Step Answer:
A rare disease called hemophilia impairs the blood's capacity to clot. Typically, it is hereditary. The majority of those with it are men. Blood that has been cut typically contains substances called clotting factors, which when combined with platelets, cause the blood to become sticky and form a clot.

Hemophilia is caused by a mutation or modification in one of the genes that codes for the clotting factor proteins necessary to form a blood clot. The clotting protein may no longer function at all or not at all as a result of this modification or mutation. The X chromosome contains these genes. Due to the fact that males only have one X chromosome, hemophilia is a hereditary condition that is X-linked and recessive in nature. Females are typically carriers since they have an extra X chromosome, however heterozygous carriers frequently exhibit hemophilia symptoms.

The haemophilia A and B have an X-linked recessive inheritance pattern. The X chromosome, one of the two sex chromosomes, is home to the genes associated with various illnesses. Males can develop the condition by having just one mutant copy of the gene in each cell (who have only one X chromosome). For the disorder to manifest in females (who have two X chromosomes), a mutation would need to arise in both copies of the gene. It is extremely uncommon for girls to have hemophilia because it is improbable that they will have two mutated copies of this gene. Fathers are not able to pass on X-linked qualities to their sons, which is a trait of X-linked inheritance.
So, option (D) is correct.



Note: A boy can only inherit the X-linked trait of hemophilia from his mother's X chromosome. The father cannot convey any of his X-linked genes to his son because he only contributes his Y chromosome, not his X chromosome.