Which one of the following processes results in the production of recombinants in future generations ? (i) Mutation (ii) Independent assortment during meiosis I (iii) Independent assortment during meiosis II (iv) Crossing over of bivalents

The correct option is (ii) and (iv).

Let us break down why independent assortment during meiosis I and crossing over of bivalents are the processes responsible for producing recombinant gametes and offspring in future generations:

1. Crossing Over of Bivalents (iv):
During Prophase I of meiosis I, homologous chromosomes pair up to form structures called bivalents (or tetrads). Non-sister chromatids of these homologous chromosomes wrap around each other and exchange genetic segments at points called chiasmata. This physical exchange of genetic material is known as crossing over. It directly breaks linkage groups and creates new, unique combinations of alleles on maternal and paternal chromosomes, producing recombinant chromatids that will later be distributed to gametes.

2. Independent Assortment during Meiosis I (ii):
During Metaphase I of meiosis I, homologous chromosome pairs (bivalents) align randomly at the metaphase plate. The orientation of each pair is completely independent of the others. During Anaphase I, these homologous chromosomes separate and move to opposite poles. Since the distribution of maternal and paternal chromosomes to the daughter cells is randomized, it generates new combinations of entire chromosomes. This process of independent assortment during meiosis I leads to huge genetic diversity and recombinant combinations in the gametes.

Why the other processes do not produce recombinants in future generations in this context:
• Mutation (i): While mutations introduce new alleles (raw genetic variations) into the gene pool, they are sudden, random changes in the DNA sequence rather than the typical sexual reproduction mechanisms (recombination) that shuffle existing alleles to produce recombinants.
• Independent Assortment during Meiosis II (iii): During meiosis II, sister chromatids (which are now single chromosomes) align at the metaphase plate and separate during Anaphase II. There is no independent assortment of homologous chromosome pairs in meiosis II, as the homologous chromosomes have already separated during meiosis I. Therefore, independent assortment does not occur during meiosis II.

Thus, the production of recombinants in future generations relies on (ii) Independent assortment during meiosis I and (iv) Crossing over of bivalents.