1.

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

Answer»

Symptoms of haemophilia: Patient continues to bleed through a minor cut as the patient does not possess natural phenomenon of blood clotting. 

Symptoms of sickle-cell anaemia: Erythrocytes lose their circular shape and become sickleshaped. As a result, the cells cannot pass through narrow capillaries. Blood capillaries are clogged and thus affects blood supply to different organs.

S. No.HaemophiliaSickle-cell anaemia
(i)It is a sex-linked recessive disorder.It is an autosomal linked recessive trait.
(ii)The gene for haemophilia is located onX-chromosome.The disease is controlled by a single pair of allele HbA and HbS.
(iii)More males suffer from haemophilia than females because in males single gene for the defect is able to express. Females suffer from this disease only in homozygous condition,i.e., Xc XcOnly the homozygous individuals for HbS , i.e., HbS HbS show the diseased phenotype.
(iv)The defective alleles produce non-functional protein which later form a non-functional cascade of proteins involved in blood clotting.Due to point mutation Glutamic acid (Glu) is replaced by Valine (Val) at sixth positions of beta globin chain of haemoglobin molecule.


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