Genetic Lottery: Meiosis and Variation

Your body runs a genetic lottery to make sure you're one-of-a-kind. It’s a process called

meiosis, which makes sperm and eggs. Inside your cells, homologous chromosomes

pair up and literally swap pieces of DNA—that’s called crossing over. Then,

these shuffled pairs line up completely randomly before the cell divides, creating even more

variation. But this high-stakes game can go wrong. Sometimes, chromosomes fail

to separate properly, a mistake called nondisjunction. This can lead to a sperm or egg with

an extra chromosome, which is the genetic reason behind conditions like Down's syndrome. It’s all in the

shuffle.