Question

How does the random alignment of homologous chromosomes during metaphase i contribute to the variation in cells produced by meiosis?

Answer 1

During metaphase I of meiosis, the random alignment of homologous chromosomes, known as independent assortment, leads to over eight million possible combinations in humans, contributing to the genetic variation in offspring.

Step-by-step explanation:

The process of meiosis serves to create gametes (sperm and eggs) with half the number of chromosomes of the parent cell. Independent assortment during metaphase I of meiosis significantly contributes to genetic variation. This randomness is because, in each cell that undergoes meiosis, the random alignment of homologous chromosomes at the metaphase plate ensures that different combinations of chromosomes are distributed to the daughter cells, leading to genetic diversity.

Each chromosome pair aligns at the metaphase plate with equal probability to face either pole. The possible number of alignments is 2n, where 'n' represents the number of chromosome pairs. In humans, this results in over eight million possible combinations from this mechanism alone, not including additional variation from crossover events. This random orientation ensures that no two haploid cells will have the same genetic makeup, bolstering the variation seen in the offspring.

Answer 2

The variation in cells produced by meiosis occurs because of crossing over that takes place during pachytene, a substage of Prophase I.

Step-by-step explanation:

Meiosis I is consist of four stages Propase I, Metaphase I, Anaphase I and Telophase I.

Prophase I of Meiosis I has five substages namely; Leptotene,Zygotene, Pachytene, Diplotene and Diakinesis.

Leptotene. Each chromosomes has two long threads of sister chromatids as result of replication during the S phase of the cycle.

Zygotene.The pairing of chromosomes begin. Pair of chromosomes are called homologous chromosomes.

Pachytene. Chromosomes are thick due to repeated coiling.Crossing over takes place during this stage where a segment of sister chromatid of one chromosome is exchange with the same segment of the sister chromatid of the homologous chromosomes through the formation of a cross-linkage of the segments called chiasma. After crossing over, the sister chromatids of each chromosome is no longer identical with each other based on the genetic material that they contain. This is the very reason why there is variation in the cells produce by meiosis. .

During metaphase, paired chromosomes simply align themselves at the equatorial plate.