There seem to be two different concepts: one is the recombinant frequency and then there's crossover frequency. These two seem to be used interchangeably whenever someone asks but I think these are two distinct concepts.
So for recombinant frequency, it is defined as the number of
(recombinant genotypes/total number of genotypes) * 100
and this frequency can never be higher than 50% because, at any one time, only 2 out of 4 chromatids are involved in crossing over, and if this happens in every meiosis, only up to 50% of gametes will contain the recombinant alleles.
But often, when people ask what about the crossing over frequency, people tend to also answer that this can never be higher than 50% and use the same explanation for the recombinant frequency to explain. But I think this is wrong. Imagine if we have 2 alleles at two ends of 1 chromosome, and a crossing over event always happens between these two alleles, then the crossing over frequency can be 100% of the time. Obviously, in reality, this could never happen because if two alleles are at the opposite ends of a chromosome, there bout to be cases where multiple crossing over events happen in between these two alleles, and some will result in these two alleles being brought back together, thus reducing the crossing over frequency. But in theory, it can be higher than 50%.
What do you think of this explanation? I'm trying to understand these concepts better.
Thank you
It well known that it is 50% , but some other cases could be reported !!. Regards.
What you said is recombinant frequency which i have explained. But what I ask is crossing over frequency.
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