Answer:
23 pairs of chromosomes (46 individual chromosomes) are redued to 23 individual chromosomes in meiosis I.
During Meiosis I
Explanation:
Meiosis is a type of cell division that results in four daughter cells with each having half the number of chromosomes as in the parent cell. During meiosis, cell division occurs twice because before the two halves of a duplicated chromosome (sister chromatids) is separated, it still needs to separate homologous pair of chromosomes, which is a similar but non-identical pair of chromosomes received from both parent. Hence, meiosis occurs in a two step division process; Meiosis I and Meiosis II.
Note that, a diploid cell contains 23 pairs of chromosomes ( 46 chromosomes in total). Each pair of chromosome is from the haploid gamete produced by each parent after meiosis.
Before going into meiosis I, the cell must first undergo growth and replicate its DNA in the interphase stage just like in mitosis. In the Prophase I of meiosis I, chromosomes condense as in mitosis but also pair up. Each chromosome aligns with its homologue pair to form a structure called TETRAD or BIVALENT.
Homologous pairs, not individual chromosomes (23 pairs in number) line up at the metaphase plate for separation during metaphase I.
In anaphase I, the homologues are pulled apart by the spindle fibres and move apart to opposite ends of the cell. The sister chromatids of each chromosome, however, remain attached to one another and don't come apart. Hence, the cell now has 23 chromosomes on one side of the cell, and another 23 on the other side.
After cytokinesis (division of the cytoplasm) in meiosis I, two daughter cells are produced and each now possesses 23 individual chromosomes (haploid) different from the parental 23 pairs (diploid).
N.B: Sister chromatids separate in the anaphase of meiosis II, where each chromatid is counted as an individual chromosome.
