Genetics

[ohkos1]

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I was wondering how the distance between specific loci change?

For example a hypothetical: if eye color was on gene A and pupil size on gene B, the distance between gene A and gene B is 50 cM. Is there a scenario where A and B is not 50?

I'm having trouble visualizing it.

Thanks

 

[jcb123]

50 cM is the maximum distance you can measure between loci. It represents a 50% recombination frequency. It's the maximum distance because if you have two genes on different chromosomes there will be 50% chance that the alleles will be passed along together and 50% chance they will be recombined.

So a situation where it's not 50 would be if the genes are on the same chromosome. aka linkage

 

[ohkos1]

Okay I realized after reading that I made a bad example. What if it was 5 cM? What I don't understand is if it's possible to change the distance between specific genes during recombination. If the distance between 2 genes is 5 cM, is it possible to change it to 2 cM or 10 cM?

 

[jcb123]

No it's not going to change. Whenever you see those units u can think 5 cM means a 5% chance of recombination. But the distance between genes will change .... Unless there is some sort of deletion, duplication, translocation or any other sort of mutation. But I doubt an mcat question would get that complicated.