Chromosome Q - Alpha Test

Hi, could someone explain why this diagram shows translocation. Found this in the alpha test question book

oh hey! i’m reposting my answer as someone else had asked it previously:

B) C) and D) would explain a change in genotype not karyotype

E) is wrong as homologous recombination happens with 2n=4 chromatids, (and the image does in fact show a chromosome undergoing homologous recombination with 2n=4). All the chromatids are accounted for.

A) we are left with this option by elimination, translocation is a type of karotype modification so it could be a possible answer.
in my opinion we wouldn’t necessarily see a translocation of a portion of another chromosome on the diagram, unless it was a translocation of an entire p or q arm which would be much more obvious to see

Does someone have a better explanation for A?

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Ooo thank you for explaining about the elimination method of why the others were wrong! But yess if the options were different I would like to know how A corresponds to the diagram. Maybe its because of the difference in length?

yeah if we could see a difference in length it could give us a clue that there has been a translocation, but be careful acrocentric chromosomes exist and look super uneven just like here without having undergone any translocation

Oooo does that happen for only homologous chromosomes? Because in this question we can distinguish they’re non homologous. Thank you for letting me know about the acrocentric chromosomes!

(also this is the first time i try to upload a photo from imgur i hope it works)


It works! Thank you for the solution, this diagram helps a lot

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Nicee, thank you! I see it there as well.

Btw is there anything more we should study in terms of crossing-over of homologous chromosomes other than crossover values (COVs) and translocation?

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hey! you’re right it’s for homologous chromosomes i got confused :sweat_smile:

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In terms of crossing over, there’s not much to learn I think - just what it is, how to identify it on a diagram and which part of the chromatid and we should know when it occurs in the meiosis cell cycle. Also, knowing the difference between crossing over and independent assortment :)) Hope this helps! The Edexcel A-Levels book was really helpful in this section


Ahh I see, thank you very much:)