Q.During anaphase-I of meiosis

Meiosis I: Metaphase and Anaphase

Imagine you have two pairs of shoes — one pair of sneakers and one pair of formal shoes. Each pair is a set of two matching shoes (left and right). Now, you need to separate the pairs so that each of two boxes gets exactly one sneaker and one formal shoe. That is the job of Meiosis I: separate the pairs, not the individual shoes.

The Setup: Metaphase I

By the time a cell reaches Metaphase I, each chromosome has already duplicated into two identical sister chromatids (like the left and right shoe of the same type, still stuck together). But the key is that homologous chromosomes — the two copies of the same chromosome, one from your mother and one from your father — have paired up into structures called bivalents (or tetrads). Each bivalent contains four chromatids total.

In Metaphase I, these bivalents line up along the equator of the cell — the metaphase plate. But here is the crucial difference from mitosis: the bivalents align as pairs, not as individual chromosomes. The two homologous chromosomes of each bivalent sit on opposite sides of the plate, facing opposite poles. The spindle fibres from one pole attach to one whole chromosome (both its sister chromatids), and fibres from the other pole attach to the other whole chromosome.

The Action: Anaphase I

Now comes the separation. In Anaphase I, the spindle fibres shorten and pull the whole homologous chromosomes apart — each chromosome (with its two sister chromatids still attached) moves as a unit toward one pole. The sister chromatids do not separate from each other yet. That separation happens in Meiosis II.

So at the end of Anaphase I, each pole has received one complete set of chromosomes, but each chromosome is still doubled (two chromatids). The cell now has half the original number of chromosome types, but each chromosome is still in duplicate form. …