|MadSci Network: General Biology|
Let me see if I follow how you came up with your answer. There are 23 pairs of chromosomes in each parent, and only one of each pair is transmitted to each kid. So the probability of transmitting the same 46 chromosomes from 46 pairs is 1 in 2^46, assuming equal transmission probabilities for each chromosome in each pair. Well, technically you're wrong due to biology not statistics. For each pair of chromosomes in a parent, it is rather likely that the transmitted chromosome is not identical to either of the parental chromosomes, but rather is a hybrid of the two parental chromosomes. This is due to a biological phenomenon called recombination, where genetic information is traded between the parental chromosomes during meiosis. The probability of a recombination event is ~1 for each chromosome pair in each meiosis. The likelihood of recombination in "exactly" the same spot (such that the recombinant chromatids in 2 kids are the same) is virtually nil. In order for such an event to occur, the crossovers would have to take place within about 1500 bp of each other (the average distance between polymorphisms) on a 150 million bp chromosome. Take this likelihood and figure 23 pairs of chromosomes crossing over once in each parent, and the probability of genetically identical children from a given pair of parents is considerably smaller than 1 in 2^46. Chris Carlson firstname.lastname@example.org
Try the links in the MadSci Library for more information on General Biology.