Answer:
The correct answer is: homologous chromosomes.
Explanation:
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).
Two chromosomes are homologous when they belong to the same pair and have the same genetic information, although they can have a few variations. These variations from one homologous chromosome to the other are called alleles 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.
This is the basis for Mendelian inheritance.
