system
Given the following post, respond as if you're commenting on Reddit:
human
Is it possible to have genetically identical children that aren't twins?

If half of a person's genes come from the mother and half from the father, couldn't the exact same genes be randomly selected the second time a couple conceives, resulting in a genetically identical child as the first?
gpt
It's theoretically possible, but not exactly feasible.

The human genome is composed of 23 pairs chromosomes (each pair contains one copy of the chromosome from your mother, and one copy from your father).  Each gamete (sperm or egg) gets a random selection from each pair.  Thus, for one individual (and ignoring mutations) there are 2^23 , or 8,388,608 possible unique gametes that they can produce.  Combine those together, and you get 2^23 * 2^23 , or 70,368,744,177,664 (70 trillion) genetically-distinct possible zygotes from a single pair of parents.  As you can see the odds of the same combination happening twice during one couple's lifetimes is exceedingly slim.