What is the difference between homozygous and heterozygous ?

The key difference between homozygous and heterozygous lies in the genetic makeup of an individual:

Homozygous:

– An individual has two copies of the same allele (gene) for a particular trait, one from each parent.
– The genotype is represented by two identical letters (e.g., AA or aa).
– The individual will always express the trait associated with the allele.

Heterozygous:

– An individual has two different alleles for a particular trait, one from each parent.
– The genotype is represented by two different letters (e.g., Aa or aB).
– The individual may or may not express the trait associated with one of the alleles, depending on the dominance or recessiveness of the alleles.

In summary:

– Homozygous: Two identical alleles (AA or aa)
– Heterozygous: Two different alleles (Aa or aB)

This difference affects how traits are expressed and inherited, and is a fundamental concept in genetics!