Eli5: Would any of the 250 million sperm I outraced into existence, have been, in any meaningful way different different than I turned out?

Question

We often hear the metaphor, “out of the millions of sperm, you won the race!” Or something along those lines. But since the sperm are caring copies of the same genetic material, wouldn’t any of them have turned out to be me?

(Excluding abiotic factors, of course)

In: Biology

Answer 1

You’ll usually learn this in Grade 11/12 biology. Basically during the making of the sperm cell (in a process called meiosis) there is a step called a ‘crossover’ where your ancestral DNA will line up with each other (crossing over) and exchange genetic information in a randomizing process to create more different types of sperm (increasing genetic variability or genetic differences). As a result, it is highly unlikely any of those millions of sperm cells will have an exact match because your nature tried to randomize the results to produce more varied offspring to offer a better chance of survival. If everyone had the same DNA, the same disease/weakness would kill all of us, so nature likes to make us all very different if it can to increase the odds of survival.