Locus refers to the position of what on a chromosome, which controls the characteristics of an organism?
rna
genome
gamete
gene
Today, we known that characteristics of organisms are controlled by genes on chromosomes (see Figure below ). The position of a gene on a chromosome is called its locus . In sexually reproducing organisms, each individual has two copies of the same gene, as there are two versions of the same chromosome ( homologous chromosomes ). One copy comes from each parent. The gene for a characteristic may have different versions, but the different versions are always at the same locus. The different versions are called alleles . For example, in pea plants, there is a purple-flower allele ( B ) and a white-flower allele ( b ). Different alleles account for much of the variation in the characteristics of organisms.