Question

Read the following statements and choose the correct option.
I. In phenylketonuria the affected person does not secrete the enzyme to convert phenylalanine to tyrosine
II. Possibility of male becoming haemophiliac is extremely rare
III. Sickle cell anaemia is caused by the substitution of glutamic acid by valine at fifth position of beta chain of haemoglobin
IV. Myotonic dystrophy is an autosomal dominant trait.

• A. I and II alone are wrong
• B. II and III alone are wrong
• C. II alone is wrong
• D. III alone is wrong
• E. II and IV alone are wrong

Answer 1

Answer: (B)

II and III alone are wrong

• Phenylketonuria is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body. It is caused by a defect in the gene that helps create the enzyme needed to break down phenylalanine. Hence statement I is true.
  
• As a recessive X-linked genetic disorder, the mutation that causes hemophilia is passed to offspring via the X chromosome. Hemophilia is more common among male children because they only inherit one X chromosome. ... In males, there is both an X chromosome and a Y chromosome, whereas females have two X chromosomes. Hence statement II is false.
• Sickle-cell anemia is caused by a point mutation in the β-globin chain of hemoglobin, causing the hydrophilic amino acid glutamic acid to be replaced with the hydrophobic amino acid valine at the sixth position. Hence, statement III is false.
• Myotonic dystrophy is an autosomal dominant disorder which is typically inherited from a person's parents. Hence, statement IV is true.

So, the correct answer is 'II and III alone are wrong'.