What is the difference between phenotype and genotype?

An individual's genotype is the allelles which they have inherited (alleles are different versions of genes). An individual's phenotype is the characteristics that their genotype codes for. What a genotype looks like in the phenotype depends on whether alleles are dominant or recessive. Dominant alleles are represented by a capital letter and they are always expressed in the phenotype, even if there is only one present. Recessive alleles are represented by a lowercase letter and they are only expressed in the phenotype if two copies are present.Taking eye colour as an example: A is a dominant allele and codes for brown eyes, a is a recessive allele and codes for blue eyes. If an individual has genotype AA, they have a phenotype of brown eyes. If an individual has genotype Aa, they have a phenotype of brown eyes.If an individual has genotype aa, they have a phenotype of blue eyes.Other key words to look out for: 'homozygous' and 'heterozygous'.I can show an example using a punnet square using the whiteboard.

Answered by Anna H. Biology tutor

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