Question

Pick out the correct statements.
a. Haemophilia is a sex-linked recessive character.
b. Downs syndrome is due to aneuploidy.
c. Phenylketonuria is an autosomal dominant genetic disorder.
d. Phenylketonuria is an autosomal dominant genetic disorder.
e. Sickle cell anaemia is an X-linked recessive disorder.
A. a, b, d correct
B. a, c, e correct
C. a, c correct
D. b, e correct
E. a, d, e correct

Answer 1

Haemophilia is a type of a genetic defect caused due to mutant allele located on X-chromosomes, Down's syndrome is a type of an autosomal syndrome caused due to trisomy of ${21^{{{st}}}}$ autosome, Phenylketonuria is a type of congenital genetic disorder due to the accumulation of phenylalanine in blood.

Complete answer:
Haemophilia: it is also called a bleeder’s disease or royal disease. In haemophilia, the blood delays to clot and even a minor injury caused the death of the sufferer due to excessive bleeding. It was first discovered by John Cotto. It is caused due to mutant alleles located on X-chromosomes. It is of three types: haemophilia A, B, and C.
Down’s syndrome: it was discovered by Langdon Down in 1866. It is a type of autosomal syndrome. There is a trisomy of the ${21^{{{st}}}}$ autosome. The chromosomal formula is $45A + 2H = 47$. Symptoms of this syndrome include the person is mentally retarded, short-stature, the mouth remains open with a long hanging tongue.
Phenylketonuria(PKU): it was discovered by Falling in 1934. It is characterised by the accumulation of phenylalanine or phenyl pyruvic acid in the blood. In general, phenylalanine is converted into tyrosine by an enzyme phenylalanine hydroxylase which is controlled by a dominant gene. When the genic condition becomes homozygous recessive, this enzyme is not formed and the person becomes PKU patient.
Sickle cell anaemia: it is a case of a homozygous recessive disease characterised by a condition where glutamic acid is replaced by valine at serial no. 6 in the beta chain.

The correct answer for the above question is option A.

Note:
Human beings have 46 chromosomes, out of which 44 are autosomes and 2 sex chromosomes. Human female has XX while male has XY chromosomes.
Haemophilia occurs due to presence of mutant allele on X- chromosome, where blood clotting delays.
Down’s syndrome is trisomy of ${21^{{{st}}}}$ chromosome, where the total chromosome is 47.
Phenylketonuria is because of absence of an enzyme causing accumulation of phenylalanine in blood.