Diploid species like us humans have two sets of the same 23 chromosomes: 1 set of chromosomes is inherited from our mother, the other set we inherit from our father, making up a total of 46 chromosomes in every somatic cell (sexual cells have only one set of chromosomes - they're haploid).
<u>Two chromosomes are </u><u>homologous</u><u> when they belong to the same pair and have the same genetic information, although they can have a few variations</u>. These variations from one homologous chromosome to the other are called<em> alleles</em> and represent the different phenotypic variables that can result from the same gene. If these alleles are different from one another, only one of them will express itself (there are a few exceptions, like blood type) as the organism will be heterozygous for this trait; if the alleles are the same, the individual will be homozygous for the trait.
