Which of the following is not a source of genetic variation? A. Engulfing DNA from other organismsB. Independent assortment of chromosomesC. Crossing over between sister chromatidsD. Crossing over between homologous chromosomes

C. Crossing over between sister chromatids

Explanation:

Crossing over refers to the process of exchange of a genetic segment between the non-sister chromatids of homologous chromosomes. It results in the generation of new gene combinations and adds genetic variations to the organisms.

However, crossing over between sister chromatids can not create any new gene combinations since sister chromatids are genetically identical and carry the same alleles of the genes in corresponding loci. Therefore, the exchange of a segment of chromatid between the sister chromatids of a chromosome would not add genetic variations.