Mutations and the phenotypeSpec 3.34, 3.35B, 3.36B
In short
A mutation is a rare, random change in genetic material that can be inherited. Usually it is a change in the base sequence of DNA. Mutations are one source of genetic variation, and a mutation that happens in a gamete, or in a cell that makes gametes, can be passed on to the offspring.
A mutation is a rare, random change in genetic material that can be inherited. Usually it is a change in the base sequence of DNA.
Mutations are one source of genetic variation. A mutation in a gamete, or in a cell that makes gametes, can be passed on to offspring.
Biology only (what this means)
Biology only: only in International GCSE Biology. Double Award students can skip it. What the labels meanHow a mutation can change the phenotype
Biology only (what this means)
Biology only: only in International GCSE Biology. Double Award students can skip it. What the labels mean- A change in the DNA changes the base sequence of a gene.
- This can change the sequence of amino acids in the protein that the gene codes for.
- The protein may then fold into a different shape and no longer work in the same way. For example, an enzyme's active site may no longer fit its substrate.
- The change in the protein can change the phenotype.
Biology only (what this means)
Biology only: only in International GCSE Biology. Double Award students can skip it. What the labels mean- Most genetic mutations have no effect on the phenotype.
- Some mutations have a small effect on the phenotype.
- Rarely, a mutation has a significant effect on the phenotype.
Biology only (what this means)
Biology only: only in International GCSE Biology. Double Award students can skip it. What the labels meanDo not write that all mutations are harmful. Most have no effect on the phenotype.
Written and checked against the Edexcel IGCSE Science Double Award (4SD0) specification · Updated October 2026