Class 12 NEET Biology Principles of Inheritance and Variation Questions Part 2

Sickle-cell anaemia is an autosomal hereditary disorder in which erythrocytes become sickle shaped. It is caused by the formation of abnormal haemoglobin called haemoglobin-S. Haemoglobin-S is formed when 6th amino acid of β -chain, i.e., glutamic acid is replaced by valine due to substitution. It occurs due to a single nucleotide change (A → T) in the β -globin gene of coding strand. In the normal β -globin gene the DNA sequence is CCTGAGGAG, while in sicklecell anaemia, the sequence is CCTGIGGAG.