Phenotype
Biology: Cambridge International GCSE Supplement, topic 17.3.2
Genotype vs Phenotype
When talking about the inheritance of characteristics, we use the words genotype and phenotype:
Genotype
- Genotype refers to the combination of alleles an organism has.
- If the two alleles are the same, we say that the person is homozygous (BB or bb). Breeding two identical homozygous individuals is called pure-breeding.
- If the two alleles are different, we say that the person is heterozygous (Bb). Two heterozygous individuals breeding is not pure-breeding.
Phenotype
- A phenotype is an observed characteristic of an individual.
- The phenotype is determined by the interaction between the genotype and environment.
- Earlobes being attached or free is an example of a phenotype, where the alleles present will determine a characteristic, unless the environment interferes.
Test yourself on Phenotype
If the allele for a free earlobe is E (dominant) and the allele for an attached earlobe is e (recessive), what will the earlobe of a person with the genotype Ee be like?
Pure-breeding is when what type of individuals breed?