Explain how crossing over and independent alignment of chromosomes increase genetic variability?
Crossing over and independent alignment of chromosomes are two mechanisms that contribute to genetic variability during the process of meiosis. These processes occur during the formation of gametes (sperm and egg cells) and involve the exchange and rearrangement of genetic material.
1. Crossing Over: During meiosis, homologous chromosomes (one from the mother, one from the father) pair up and align with each other. Within each pair, segments of genetic material can break and exchange places, resulting in a genetic recombination. This exchange occurs at specific regions called chiasmata.
By exchanging genetic material, crossing over creates new combinations of alleles (different versions of genes) between homologous chromosomes. This shuffling of genetic information leads to novel combinations of traits in offspring. The farther apart two genes are on a chromosome, the more likely they are to undergo crossing over, thus increasing the genetic variation even more.
2. Independent Alignment of Chromosomes: During meiosis, homologous pairs of chromosomes align randomly along the cell equator. The orientation of each pair is independent of the other pairs. This random alignment, known as independent assortment, increases genetic variability.
Independent assortment means that one pair of chromosomes aligning a certain way does not determine how another pair aligns. As a result, the maternal and paternal chromosomes segregate randomly when they separate during the formation of gametes. This random distribution leads to various combinations of chromosomes in the resulting gametes, further increasing genetic diversity.
To sum up, crossing over and independent alignment of chromosomes during meiosis contribute to genetic variability by shuffling and recombining genetic material, creating new combinations of alleles and distributing maternal and paternal chromosomes randomly.