Question

Write the symptoms of the haemophilia and sickle cell anaemia in humans. Explain how the inheritance pattern of the two diseases differs from each other.

Answer 1

Hint: Sickle cell anaemia is inherited red blood disorder in which there is deficiency of red blood cells for transporting oxygen in the body. Whereas, haemophilia is an inherited genetic disorder in which the person’s blood doesn't clot leading to excessive loss of blood.

Complete answer:
- Sickle cell disease is a genetic disease which is caused due to molecular mutation of gene haemoglobin on chromosome 11 which produces the beta chain of adult haemoglobin. The mutated gene Hbs produces sickle cell haemoglobin.
- In the sickle cell anaemia, the 6th amino acid i.e, glutamic acid, in the beta chain of normal haemoglobin is replaced by valine. The children that are homozygous produce rigid chains. When the oxygen level of the blood drops below a certain level, RBC undergoes sickling.
- Such cells do not transport oxygen efficiently, they are removed by spleen causing severe anaemia. Sickle cell is an autosomal linked disease in which both male and female progenies can be equally affected.

- Haemophilia may be a largely genetic inherited disorder that impairs the body's ability to create blood clots, a method required to prevent haemorrhage.
- Haemophilia is a sex-linked disorder. In haemophilia, the blood fails to clot when exposed to air and even a small skin injury results in continuous bleeding and can lead to death from the loss of blood.
- The recessive X linked gene for haemophilia shows characteristic criss-cross inheritance. It's a single gene in male results and disease haemophilia, where a woman needs two such genes for the same.

Differences between Haemophilia and Sickle-cell anaemia:

S.No	Haemophilia	Sickle cell anaemia
1.	It is a sex-linked recessive disorder.	It is an autosomal linked recessive trait.
2.	More males suffer from haemophilia than females because a single gene for the defect is able to be expressed. Females suffer from this disease only in homozygous condition, i.e., Xc Xc.	Only the homozygous individuals for HbS, i.e., HbS HbS.

Note: Due to point mutation Glutamic acid (Glu) is replaced by Valine (Val) at sixth positions of a beta-globin chain of haemoglobin molecules.