Q. Pick out the correct statements :
(a) Haemophilia is a sex-linked recessive character.
(b) Down’s syndrome is due to aneuploidy.
(c) Phenylketonuria is an autosomal recessive gene disorder.
(d) Sickle cell anaemia is an X-linked recessive gene disorder.
(i) (a) and (d) are correct
(ii) (b) and (d) are correct
(iii) (a),(c), and (d) are correct
(iv) (a),(b) and (c) are correct
Solution :
Correct option : D Hemophilia A and hemophilia B are inherited in an X-linked recessive pattern. The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. Sex-linked diseases are passed down through families through one of the X or Y chromosomes. X and Y are sex chromosomes Aneuploidy refers to a condition when there is an abnormal number of chromosomes. Down syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21.PKU is an autosomal recessive disorder, caused by mutations in both alleles of the gene for phenylalanine hydroxylase (PAH), found on chromosome 12. In the body, phenylalanine hydroxylase converts the amino acid phenylalanine to tyrosine, another amino acid. Sickle cell anemia is inherited as an autosomal (meaning that the gene is not linked to a sex chromosome) recessive condition. This means that the gene can be passed on from a parent carrying it to male and female children. So, the correct answer is ‘a,b,c’ .
