# Whole chromosome preservation through generations

1. Nov 30, 2009

### nobahar

Hello!
I have a peculiar question concerning, as the title states, whole chromosome preservation through the generations.
I'll include my reasoning in case you need to point out any discrepancies.
During meiosis, crossing over occurs between non-sister chromatids. Two of the chromatids from homologous chromosomes are therefore preserved, although they will seperate into different gametes. The chances of you obtaining a complete chromosome that has not been subjected to crossing over is $$\frac{1}{4}$$ for any one chromosome. Am I correct to assume then, that the chances of your sharing any one complete chromosome in common with an ancestor is $$(\frac{1}{4})^n$$? Where n is the number of generations you work backwards?
Aplogies, I think it should be $$\frac{1}{2}$$. As an 'intact' (i.e. passed on from the previous generation without being subjected to crossing over) chromosome is an 'intact' chromosome, and I suppose I shouldn't discriminate against the two homolgous chromosomes.