The result of exchanging alleles is genetic recombination between non-alleles. For example, B and b are interchanged. Before the interchange, the sister monomer is AB, and after the interchange, it is Ab. This is genetic recombination. Bb is allelic, aA and bB are non-allelic.

For the phenotype of the same trait, each of several non-alleles has only a partial influence. Such several genes are called additive genes or polygenes. Among the additive genes, each gene has only a smaller phenotypic effect, so it is also called a minimally effected gene. Compared with small-effect genes, genes that determine a certain trait are determined by a single gene.

Extended information:

Since the number of chromosomes in each organism is certain, the number of pairs of their homologous chromosomes is also certain. For example, peas have 14 chromosomes and 7 pairs of homologous chromosomes. Homologous chromosomes often contain different alleles, which are exchanged during meiosis and randomly assigned to different sex cells, which is of great significance for genetic recombination.

Sister chromatids are two parallel chromatids connected by a centromere. They are formed by duplication of the same chromosome during interphase of cell division. The two chromatids The DNA sequences are completely identical.

Although they are the same shape and size, one does not come from the father and one comes from the mother, so sister chromatids are not homologous chromosomes. The DNA sequences of the two monomers of homologous chromosomes are different and originate from the parents respectively.

Baidu Encyclopedia--Homologous chromosomes

Baidu Encyclopedia--Non-allele