Final answer:
The diagram illustrates the method of crossing over, where non-sister chromatids of homologous chromosomes exchange DNA segments during prophase I of meiosis. Along with independent assortment during metaphase I and random fertilization, it contributes to genetic variation in offspring. The correct option is a. Crossing over
Step-by-step explanation:
The diagram described is illustrating the process of crossing over. This occurs during prophase I of meiosis when homologous chromosomes pair up to form tetrads. During this pairing, non-sister chromatids of these homologous chromosomes can exchange segments of DNA.
The entities between which crossing over occurs are the non-sister chromatids of homologous chromosomes. This recombination results in chromosomes that possess a mixture of maternal and paternal genetic material, which contributes to genetic variation in offspring.
Independent assortment is the random orientation of chromosome pairs during metaphase I of meiosis. This leads to a different combination of chromosomal sets in gametes, further contributing to genetic variation. Fertilization is the union of these diverse gametes, resulting in offspring with a unique set of genes.
Unlike independent assortment and crossing over, fertilization is not a process of recombination within a single individual, but rather the combination of genetic information from two individuals.
Altogether, crossing over, independent assortment and random fertilization are major drivers of genetic variation in sexually reproducing organisms. For example, in humans, these processes lead to millions of different potential combinations of chromosomes. The correct option is a. Crossing over