Homozygous
Not all types of a particular gene are the same, and different forms of the same gene are called alleles. For example, one allele can carry instructions to give individual brown eyes, while another allele may not have completely the same instructions. This can result in a mutation which produces a different eye colour than the standard brown, such as blue or green. Chromosomes are DNA and protein structures which are found in cells.
Homologous chromosomes are chromosomes within a biological cell which pair up. The chromosomes that are non-identical contain the information regarding the person's biological features. They may contain the same genes at any point on the chromosome, but have different alleles – (i.e different information at that point). Humans have twenty two pairs of non-sex chromosomes, and each pair is inherited from one of their two parents. When identical alleles of each gene are present on both homologous chromosomes, it is referred to as Homozygous.
When these two matching alleles are present, this means that the trait which the alleles represent will be dominant. For instance, brown eyes may result from both alleles having information regarding producing brown eyes, or it may mean that one of the alleles has dominant information. This is known as a homozygous dominant organism. The weaker of the two alleles which may have no bearing on the resulting trait will be said to be recessive. A true breeding organism is an organism which passes on all of its biological traits to subsequent generations. To be able to pass on these traits the organisms are always homozygous.
