# Allele

A different version of the same gene. For example, a gene for eye colour has more than one allele.

Biology (school) · Part 05: Genes and inheritance · Card 4 of 11 · Last updated 2026-10-19

## Analogy

Chocolate and vanilla are different versions of the flavour 'ice cream'.

## In practice

One allele for a flower gene might give red petals and another white petals.

## Practice

### Flashcards

- **What is an allele?** A different version of the same gene.
- **What does heterozygous mean?** Having two different alleles for a gene, such as Tt.

### Interview questions

**Explain how a Punnett square is used to predict the outcome of a genetic cross.**

- Write the parents' alleles along the top and side
- Fill in each box with the allele pairs from both parents
- Work out the genotype of each box
- Count boxes to get probabilities or a ratio

## Questions people ask

### Where do alleles come from?

New alleles arise by mutation, a change in the DNA sequence of a gene. Once an allele exists, it can be passed on from parents to children. You get one allele of each gene from each parent, so most people carry two alleles for each gene, which may be the same or different.

### What is the difference between a gene and an allele?

A gene is the section of DNA that controls a feature, such as hair colour. An allele is one particular version of that gene, such as the allele for black hair or red hair. Everyone has the same genes, but different people may have different alleles.

## Related concepts

- [Genotype and phenotype](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-6)
- [Punnett square](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-7)
- [DNA](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-1)
- [Gene](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-2)

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