Haemophilia
(i) It is a ***-linked recessive disorder.
(ii) Patient continues to bleed even on a minor cut as the patient does not possess natural phenomenon of blood clotting.
(iii) The gene for haemophilia is located on X-chromosome.
(iv) So more males suffer from haemophilia than females because in males single gene for the defect is able to express.
(v) The defective alleles produce non-functional protein which later form a non-functional cascade of protein involving in blood clotting.
(vi) Females suffer from this *** only in homozygous condition, i.e., XcXc
Sickle-cell Anaemia
(i) It is an autosomal linked recessive trait.
(ii) The *** is controlled by a single pair of allele HbA and Hbs
(iii) Only the homozygous individuals for Hbs , i.e., Hbs Hbs show the diseased phenotype.
(iv) The heterozygous individual are carriers (Hba Hbs ).
(v) Due to point mutation Glutamic acid (Glu) is replaced by Valine (Val) at sixth positions of beta globin chain of haemoglobin molecule.
(vi) Hbs behaves as normal haemoglobin except under oxygen stress where erythrocytes lose their circular shape and become sickle-shaped. As a result, the cells cannot pass through narrow capillaries. Blood capillaries are clogged and thus affects blood supply to different organs.
