Gene mutations involve a change in the base sequence of chromosomes
A gene mutation is a permanent change to the sequence of DNA bases in a chromosome. This change alters the genetic instructions carried by that gene.
Real World
Sickle cell anaemia is caused by a single base change in the gene coding for haemoglobin — adenine is replaced by thymine — changing one amino acid (glutamic acid → valine) and causing red blood cells to deform under low oxygen conditions.
Exam Focus
Always specify that mutations change the base sequence of DNA, not just 'the gene'; vague answers about 'changing DNA' rarely score full marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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