Describe how mutations can lead to genetic variation within a population of organisms.

Edexcel GCSE Biology (1BI0) — 3.5 Variation and mutation · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

A population of bacteria was exposed to ultraviolet (UV) radiation. After several generations, scientists observed that some bacteria in the population had developed new characteristics not seen in the original population.

Model answer (4 marks)

A mutation is a random change in the base sequence of DNA

Mutations may produce new alleles (versions of a gene)

Different alleles can lead to differences in the proteins produced or coded for

This results in differences in phenotype or observable characteristics between organisms in the population

Examiner tips

Use the exact wording from the mark scheme – e.g. ‘random change in the base sequence of DNA’ and ‘new alleles’
Show the logical sequence: mutation → new allele → altered protein → altered phenotype
Keep each point concise – one sentence per point is sufficient for full marks

Common mistakes

Using vague terms such as ‘mutation causes change’ without specifying DNA base change
Confusing mutation with natural selection or genetic drift
Writing more than four points or adding unnecessary detail

Mark scheme (4 marks)

A mutation is a random change in the base sequence of DNA
Mutations may produce new alleles (versions of a gene)
Different alleles can lead to differences in the proteins produced / coded for
This results in differences in phenotype / observable characteristics between organisms in the population

Key terms in this question

mutation · genetic variation