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Autosomal Linkage

could Ab and Ba alleles of two genes be linked? all i see on diagrams is AB and ab being linked :s
Original post by Asad_2015
could Ab and Ba alleles of two genes be linked? all i see on diagrams is AB and ab being linked :s


Do you mean can a dominant allele for one gene sit alongside a recessive allele for another gene so that they are linked? If so, then sure they can. My guess would be that examples don't show this simply for clarity. If I'm not understanding your question, then can you explain a bit more? In either case, an example would make me more confident in my answer?
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Asad_2015
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Original post by OxFossil
Do you mean can a dominant allele for one gene sit alongside a recessive allele for another gene so that they are linked? If so, then sure they can. My guess would be that examples don't show this simply for clarity. If I'm not understanding your question, then can you explain a bit more? In either case, an example would make me more confident in my answer?


Yes that's what i mean, i was thinking they can be together. But every example shows A and B together.
I've noticed that AB and ab are often paired. It is recurring on the WJEC syllabus too.
From what I have seen, it's to make it easier for the marker. For example, on this specimen paper :

http://www.alevelbiologytutor.com/tutoring-blog/2016/11/21/autosomal-linkage-try-with-3

the linked alleles are represented as T, D, R, on one chromosome and t,d,r, on the other i.e. it's a heterozygote at all these loci.

In real life, it would be entirely possible for the individual to have TdR on one chromosome and tDr on the other (for example), so that it is still heterozygous at all loci. In fact, in this example, this is what you end up with on one or more chromatids following the crossing over at prophase I

I think it is presented like this in teaching and exam materials because it makes it easier to mark - you can see at a glance that the student has done the crossing over correctly.

Hope that makes sense

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