(a) Write in detail about the following Mendelian disorders (i) Thalassemia (ii) Albinism

Explanation

Thalassemia is an autosomal recessive disorder . It is caused by gene mutation resulting in excessive destruction of RBC.s due to the formation of abnormal haemoglobin molecule . Normally haemo is composed of four poypeptide chains , two alpha and two beta globin chains . Thalassemia patients have defects of four polypeptide chains , two alpha and two beta globin chains . Thalassemia patients have defects in either tha alpha or beta globin chain causing the production of abnormal haemoglobin molecules resulting in anaemia .
Thalassemia is classified into alpha and beta based on which chain of haemoglobin molecule is affected . It is controlled by two closely linked genes HBA 1 and HBA 2 on chromosome 16 . Mutation or deletion of one or more of the four alpha alleles causes Alpha Thalassemia . In Beta Thalassemia , production of beta globin chain is affected . It is controlled by a single gene (HBB) oon chromosome 11 . It is the most common type of Thalassmia and is also known as Cooley.s In this disorder , the alpha chain production is increased and damages the membranes of RBC .
b Albinism
Albinism is an inborn error of metabolism , caused due to an autosomal recessive gene . Melanin pigment is responsible for skin colour . Absence of melanin results in a condition called albinism . A person with the recessive allele lacks the tyrosinase enzymes system . which is required for the conversion of dihyroxypphenyl 1 alanine (DOPA) into melanin pigment inside the melanocytes . In an albino , melancytes are present in normal numbers in their skin , hair iris , etc ., but lack melanin pigment .
3,4 -underset ((DOPA)) ( dihydroxy) phenylaline overset ("Tyrosinase ") to Melanin .