Mapping genes with a three point testcross

[@nicholassheldon4682]

Why don't you calculate a/b recombinants?

[@g_5083]

How did you find out which ones were the A/C recombinants?

[@roronoaz4lyfe1947]

Same question I had. This guy does not explain these concepts well. Still confused.

[@abdullahmohammad6803]

If the genotypes do not match the parental genotype, it is a recombinant genotype.

[@abdullahmohammad6803]

Supposed the parent has AC or ac genotypes, so if the offspring’s genotype matches that. It is non-recombinant offspring. But we can see that the genotype aCB and Acb do not match the parents’ genotype. ( like I said it must be AC or ac , instead it is aC and Ac) So it is a recombinant genotype , product of crossing over.

[@shivi3132]

if you still need an answer, it's bc to exchange C (which is in the middle of the other 2) we'd need a double crossing-over, which means that the chromosomal region between both A and C and C and B would need to make contact to exchange the C and c allele, giving us AcB and aCb. All this to say, when A and C have a crossing over event, it is a "single crossing-over event" during which only the A allele is exchanged, giving us aCB and Acb. you can tell that A was the allele exchanged in this cross bc it's the odd one out, CB are dominant alleles whereas a is recessive and vice versa

[@violet3418]

Hi. Aren't double recombinants AbC and aBc? The ABc and abC are just single recombinants, I would say.

[@BrianTeague00]

In a three-point test cross, the two most abundant classes of progeny are ALWAYS the parental type and the two least abundant classes are ALWAYS the double-recombinants. That's because recombination is infrequent, and seeing TWO recombinations is even more so.

[@BellaS1016]

thank you! great explanation

[@g_5083]

Hi do you think you could explain how to find out which ones were the A/C recombinants? 5:00

[@natalyaanderson6923]

amazing this helped so much thank you

[@szxnv]

:)