# Genotype and phenotype

Genotype is the alleles an organism has. Phenotype is the feature you can see, such as eye colour.

Biology (school) · Part 05: Genes and inheritance · Card 6 of 11 · Last updated 2026-10-19

## Analogy

Genotype is the recipe. Phenotype is the cake.

## In practice

Two plants with genotypes TT and Tt both have the same phenotype: tall.

## Practice

### Flashcards

- **What does heterozygous mean?** Having two different alleles for a gene, such as Tt.
- **What is the difference between genotype and phenotype?** Genotype is the alleles you have. Phenotype is the feature you show.

### 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

### What do homozygous and heterozygous mean?

Homozygous means having two identical alleles for a gene, such as TT or tt. Heterozygous means having two different alleles, such as Tt. A heterozygous person shows the dominant feature, but can pass on the recessive allele and is called a carrier if the allele causes a disorder.

### Does the environment affect phenotype?

Yes. Phenotype comes from genes and the environment together. Two identical twins have the same genotype, but one who exercises will be stronger. A plant with genes for tallness will still stay short without enough light or water. Many features, such as height and weight, are influenced by both.

## Related concepts

- [Allele](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-4)
- [Punnett square](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-7)
- [Dominant and recessive alleles](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-5)
- [Sex chromosomes](https://studyvisually.com/learn/science/biology-school/biology-school-part-5/biology-school-part-5-concept-10)

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