Ch 5. Principles of Inheritance and Variations (Stack 4)

Question 1

What is phenylketonuria? Write two symptoms

Answer 1

This inborn error of metabolism is also inherited as the autosomal recessive trait. The affected individual lacks an enzyme that com·erts the amino acid phenylalanine into tyrosine.

Symptoms:

1. Phenyl pyruvic acid and its derivatives are excreted through urine in phenylketonuria because of its poor absorption by kidney.
2. Accumulation of Phenyl pyruvic acid and its derivatives in brain results in mental retardation

Question 2

Mention the causes and effects of phenylketonuria

Answer 2

• Cause: The affected individual lacks an enzyme that come11s the amino acid phenylalanine into tyrosine
• Effect: Phenyl pyruvic acid and its derivatives are excreted through urine in phenylketonuria because of its poor absorption by kidney.
• Accumulation of Phenyl pyruvic acid and its derivatives in brain results in mental retardation.

Question 3

Why phenyl pyruvic acid and its derivatives are excreted through urine in phenylketonuria

Answer 3

Phenyl pyruvic acid and its derivatives are excreted through urine in phenylketonuria because of its poor absorption by the kidney

Question 4

Mention the sixth codons of the beta-globin chain in normal haemoglobin and the haemoglobin of a person with sickle celled anaemia

Answer 4

Sixth codons of the beta-globin chain in normal haemoglo bin: Glutamic acid the sixth codons of the beta-globin chain of a person with sickle celled anaemia: Valine.

Question 5

What is thalassemia? Mention the types

Answer 5

Thalassemia is also an autosome-linked recessive blood disease which results in reduced rate of synthesis of one of the globin chains (a and B chains) that make up haemoglobin.

Thalassem ia can be classified according to which chain of the haemoglobin molecule is affected.

• a Thalassemia - production of a globin chain is affected.
• B Thalassemia - production of B globin chain is affected.

Question 6

Write a note on a - thalassemia

Answer 6

In a Thalassemia , the production of a globin chain is affected.

a Thalassemia is controlled by two closely linked genes HBAI and HBA2 on chromosome 16 of each parent and it is observed due to mutation or deletion of one or more of the four genes. The more genes affected, the less alpha-globin molecules produced

Question 7

Write a note on B- thalassemia

Answer 7

In B T halassemia, the production of B globin chain is affected.

In B Thalassemia is controlled by a single gene HBB on chromosome 11 of each parent and occurs due to mutation of one or both the genes.