Locus, alleles and genes

[Motivanka]

So a certain place on chromosome where gene is, it's called locus. And gene contains two allels. So in my book is said that homologous chromosomes contain set of allels and this is what confuses me. So how come is that possible if a single chromosome contains genes and each gene contain two allels. In case of homologous chromosomes it should be 4 allels that is two pairs of allels or two genes because on each chromosome there is a similar gene right ?

 

[jim mcnamara]

A gene is a set of instructions to create a protein. Diploid organisms like you and me have two sets of chromosomes in most of our cells. On each member of the pair, the chromosome there has a place where the gene lives. The locus. So this means you have two separate copies of one gene. If the genes are identical we call that homozygous. If the genes are not identical, we call that heterozyogous.

An allele is one of two or more alternative versions of a gene that arise by mutation and are found at the same place (locus) on a chromosome in different individuals.