Question

What is mutation? Explain with an example.

Hint:

Sickle cell anaemia = one base change, one amino acid change, big effect.

Answer 1

Step 1: Definition:
Mutation is a sudden, heritable change in the nucleotide sequence of DNA (or in the number/structure of chromosomes) that can alter the genetic information passed on to offspring, and is a source of new variation for evolution.

Step 2: Example:
Sickle cell anaemia is caused by a point mutation in the gene coding for the beta chain of haemoglobin, where a single base substitution (GAG → GTG) causes the amino acid glutamic acid to be replaced by valine at the sixth position. This changes the shape of the haemoglobin molecule, causing red blood cells to become sickle-shaped under low oxygen tension.

Final Answer:
Mutation = heritable change in DNA sequence; e.g. the single base-pair substitution that causes sickle cell anaemia.