Many genetic genealogists, myself included, often talk about DNA segments getting “broken up” or “broken down” as they are passed from one generation to the next. But this language can be misleading, since DNA isn’t really “broken up” into pieces when it passed down; instead, a few pieces are traded between nonsister chromosomes in a process called RECOMBINATION.
Genetic recombination is a process of crossover between chromosomes during MEIOSIS (meiosis = a very specialized cell division that creates eggs and sperm for reproduction). Very early in meiosis, the cells duplicate the chromosomes. Normally, every cell has 23 pairs of chromosomes, for a total of 46 chromosomes. However, in the first step of meiosis, the chromosomes are duplicated to result in a total of 92 chromosomes. There are 4 copies of chromosome 1 (2 copies of the chromosome you got from your mother, and 2 copies of the chromosome you got from your father). There are 4 copies of chromosome 2, and so on.