The mechanics of meiosis are relatively simple: two rounds of chromosome division are completed without a round of DNA replication in between. By dividing a diploid cell twice, four haploid gametes are produced. Meiosis begins with the two matching (homologous) chromosomes (one maternal, one paternal) in a diploid cell coming together, at which point DNA may be ‘swapped’ in a process called crossing over. The first division separates one of each pair of chromosomes to two new daughter cells, which then divide directly producing four gametes which now have half the original DNA complement (haploid). The molecular mechanics of chromosome separation via the microtubules of the spindle in meiosis are pretty much the same as they are in mitosis. Numerically, sperm production considerably outstrips egg production, as a fertile human male produces 1000 sperm in the same time as a single heartbeat, whereas human females are born with around 500 eggs to last a lifetime.
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