Whole chromosome preservation through generations

[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 separate into different gametes. The chances of you obtaining a complete chromosome that has not been subjected to crossing over is $$\frac{1}{4}$$ for anyone chromosome. Am I correct to assume then, that the chances of your sharing anyone complete chromosome in common with an ancestor is $$(\frac{1}{4})^n$$? Where n is the number of generations you work backwards?
Thanks in advance.

 

[nobahar]

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.
Can anyone advance on this? Basically, I am interested in the preservation of allele combinations. From this reasoning, it doesn't seem that unlikely that an enitire chromosome would be preserved, and therefore all the alleles for the different genes that were togeather in the previous generation are togeather again in the next.

 

[Blueshift5]

Hello there! Your reasoning is mostly correct. During meiosis, crossing over does occur between non-sister chromatids, resulting in the preservation of two chromatids from homologous chromosomes. However, it is important to note that this process is not perfect and there can still be some genetic variation between generations due to mutations and other factors. Additionally, the chances of obtaining a complete chromosome that has not been subjected to crossing over is not always \frac{1}{4} for every chromosome. It depends on the specific chromosomes and their location on the homologous pair.

To answer your question, the chances of sharing a complete chromosome in common with an ancestor would indeed decrease with each generation, as the likelihood of crossing over and genetic variation increases. However, it is difficult to determine an exact probability as it would also depend on the specific genetic makeup of each individual and their ancestors. It is also important to consider that while some chromosomes may be preserved through generations, others may undergo changes or be lost altogether. Overall, whole chromosome preservation through generations is a complex process and can vary greatly among individuals and families.