Final answer:
Homologous sequences of DNA on a chromosome, referred to as alleles, are found at the same loci on homologous chromosomes and determine specific traits like blood type. These alleles can vary between the two chromosomes in a pair, leading to genetic diversity through a process known as recombination.
Step-by-step explanation:
When a chromosome carries two or more homologous sequences of DNA, these sequences are referred to as alleles. Homologous chromosomes are matched pairs found in diploid organisms, which have the same length and structure and contain the same gene sequence in the same location or locus. Each homolog of the chromosome pair comes from one parent. As such, while the genes on homologous chromosomes are the same, the alleles (the different versions of those genes) can vary. The combination of alleles, such as AA, BB, AO, or BO, determines the specific trait, like blood type.
During meiosis, homologous chromosomes can exchange segments of DNA in a process called recombination, leading to genetic diversity. This is an important feature for the inheritance of traits and contributes to the variation found within a species.