eli5: if you inherit 50% of your genes from your father and 50% from your mother, what stops you from getting two of the same gene, and missing one? also why do siblings look different?

Question

eli5: if you inherit 50% of your genes from your father and 50% from your mother, what stops you from getting two of the same gene, and missing one? also why do siblings look different?

In: Biology

Answer 1

Your DNA comes in two “sets” (you have two of every chromosome) so you actually have two copies of every gene, with one from your father and one from your mother. The set from your father will be a mishmash of roughly half of his mother’s / half of his father’s DNA, same with your mother. This happens because of the so-called “crossing over” event that happens when sperm/eggs are made. In crossing over, the mother/father set of DNA in the person exchange sections of their chromosomes to make “remixed” chromosomes. One set of these remixed chromosomes are in the sperm, another set in the egg, and that makes the two sets in each person.

This remixing is random, so siblings of the same mother and father are really getting different sections of their grandmothers’ / grandfathers’ DNA.