Question

Which of the following disorders are caused due to recessive autosomal mutations?
A)Turner's syndrome and sickle cell anaemia
B)Edward's syndrome and Down's syndrome
C)Cystic fibrosis and phenylketonuria
D)Alzheimer's disease and Huntington's chorea.

Answer 1

Hint: In autosomal recessive inheritance, the two or both the copies of the gene that occurs in each cell have mutations. The parents of an individual offspring that has an autosomal recessive condition possess one copy of the mutated gene, but they always do not show signs and symptoms of the condition.

Complete answer:
Let us have a look on the diseases given in the question:
Turner syndrome takes place as the result of the union of an abnormal O egg and a normal X sperm or a normal egg and an abnormal O sperm. The individual who is suffering from this disease has 45 chromosomes (44 + X) instead of 46.
Sickle cell anaemia occurs as a result of a defective allele on chromosome 11. In homozygous conditions, this disorder can also kill the individual. In heterozygous conditions that have different alleles it can lead to haemolytic anaemia under conditions of oxygen 60-70% deficiency.
Edward syndrome occurred as a result of the presence of an extra chromosome number 18. Down's syndrome occurs as a result of the presence of an extra chromosome number 21.
Cystic fibrosis is a recessive autosomal disorder that occurs due to the alleles present on chromosomes.
Phenylketonuria is an autosomal recessive disorder in which the homozygous recessive individuals do not have the enzyme phenylalanine hydroxylase.
Alzheimer's disease is defined as a neurodegenerative disorder caused by the assimilation of amyloid protein plaques in the brain resulting in the degeneration of neurons.
Huntington's disease is an autosomal dominant disorder that takes place due to the allele on the short arm of chromosome 4.
Hence, disorders that occurred due to recessive autosomal mutations are Cystic fibrosis and Phenylketonuria.

Hence, the correct answer is option (C)

Note: Phenylketonuria is an inborn error of metabolism that can also be inherited as the autosomal recessive trait. The affected individual does not possess a liver enzyme called phenylalanine hydroxylase that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is assimilated and transformed into phenyl pyruvic acid and other derivatives.