It's not so weird. My understanding is that genes migrating across chromosomes (translocation) isn't that common. So, to a first approximation, genes are inhe

It's not so weird. My understanding is that genes migrating across chromosomes (translocation) isn't that common. So, to a first approximation, genes are inherited as 46 indivisible units. Every generation, a given chromosome has a 50/50 chance of getting dropped. You have exactly 23 chromosomes from your mother, an expected value of 11.5 chromosomes from your maternal grandmother, expected 5.75 chromosomes from her mother... another 3 generations back and you've got less than a 50% probability of getting any chromosomes from that particular relative.