Gene of which one of the following is present exclusively on the X-chromosome in human beings.

Red and green colour blindness

The correct answer is Option (3)- Red and green colour blindness

Colour blindness is a genetic disorder that is inherited in an X-linked recessive pattern. This means that the gene responsible for colour vision is located on the X chromosome, and males have only one X chromosome, while females have two X chromosomes.

Thalassemia  is an autosome-linked recessive blood disease transmitted from parents to the offspring when both the partners are unaffected carrier for the gene (or heterozygous).

Phenylketonuria is an inborn error of metabolism is inherited as an autosomal recessive trait. The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine.

Sickle-cell anaemia : This is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carrier for the gene (or heterozygous). The disease is controlled by a single pair of allele, Hb^A and Hb^S. Out of the three possible genotypes only homozygous individuals for Hb^S (Hb^SHb^S) show the diseased phenotype. Heterozygous (Hb^AHb^S) individuals appear apparently unaffected but they are carrier of the disease as there is 50 per cent probability of transmission of the mutant gene to the progeny, thus exhibiting sickle-cell trait.