Final answer:
Mendel's law of independent assortment occurs due to the random orientation of chromosomes during meiosis I, which allows for a random combination of alleles in gametes. Recombination further increases genetic diversity, while linkage can cause exceptions to the law when alleles are closely positioned on the same chromosome.
Step-by-step explanation:
Mendel's Law of Independent Assortment: Mendel's law of independent assortment states that each pair of alleles segregates independently during gamete formation. The underlying mechanism for this behavior is the process of meiosis, specifically during meiosis I, where different homologous chromosome pairs align randomly on the metaphase plate and are then segregated into separate gametes. This random arrangement ensures that each gamete receives a random mix of maternal and paternal chromosomes and the alleles on them.Recombination further contributes to the independent assortment of alleles by shuffling alleles between homologous chromosomes, which greatly increases genetic diversity.
However, it's important to note that this law applies except when genes are located very close to one another on the same chromosome, which can result in alleles being inherited together, known as linkage. Nevertheless, given recombination and the large number of genes on separate chromosomes, the potential for independent assortment is vast, contributing to the genetic variation observed within populations.