Question

Match the human genetic disorders with the causative abnormal chromosomes.

	List I		List II
A	Sickle cell anaemia	1	Sex linked (X chromosome)
B	Colour blindness	2	Autosomal chromosome 7
C	Phenylketonuria	3	Autosomal chromosome 11
D	Cystic fibrosis	4	Autosomal chromosome 4
E	Huntington's disease	5	Autosomal chromosome 12

• A. A- 3, B- 5, C- 1, D- 2, E- 4
  
• B. A- 5, B- 1, C- 2, D- 3, E- 5
  
• C. A- 4, B- 1, C- 5, D- 2, E- 3
  
• D. A- 3, B- 1, C- 5, D- 2, E- 4
  
• E. A- 2, B- 1, C- 5, D- 3, E- 4
  

Answer 1

The correct option is D A- 3, B- 1, C- 5, D- 2, E- 4

Sickle cell anaemia is caused by a mutation in $H{b}^b$ gene, that codes the $\beta$-chain. This mutation causes replacement of A by T at the 17${}^t$${}^h$ nucleotide of the Hbb gene that changes the codon GAG (glutamic acid) to GTG (which encodes valine). The mutated allele $H{b}^s$ encodes the abnormal haemoglobin molecules which stick to one another and cause stiffness and sickle shape of red blood cells. The haemoglobin-Beta gene is located on chromosome 11. Phenylketonuria is an inborn error of metabolism that results in the inability to break down the amino acid called phenylalanine. It is caused by a mutation in PAH gene, present on chromosome 12, responsible for an enzyme called phenylalanine hydroxylase, which breaks down phenylalanine into tyrosine. Huntington's disease is an autosomal dominant disorder caused by a mutation in HTT gene, located on the short (p) arm of chromosome 4, that codes for a protein called as huntingtin. This is characterized by degradation of the nerve cells of the brain. Cystic fibrosis is caused by the mutation in CFTR gene, present on long (q) arm of chromosome 7, codes for chloride channels. Colour blindness is a genetic disorder because the governing genes are present on X-chromosome which is a sex chromosome in human. The trait is transmitted to offsprings in a sex-linked manner from mother to son and from father to daughters. Option D is the correct answer.