Question

"DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II" - How is possible? If DNA content is halved in both meiosis I and II, then should the DNA content after meiosis II be half the haploid number? I know that it's not, but I don't understand how it's possible seeing as DNA content is halved twice!

Answer 1

You have to remember that there are 2 copies of each gene on every chromosome (the sister chromatids). What happens in Meiosis 1 is that the original 46 chromosomes go each to 23, 23. However, in Meiosis 2, all we are doing is ripping each individual chromosome in half, so we still have 23 in each cell.

Meiosis 2 is very similar to mitosis in that sense. If you remember mitosis, we put all 46 chromosomes in the middle, and rip each one in half. Same thing for Meiosis 2.

In meiosis1 we line the chromosomes up in the middle in pairs, so we have 2 lines of 23 instead of one line of 46