Independent assortment leading to variation in meiosis help
Hi please may I have some help I am really confused and I am struggling to word this question for my teachers to understand what I mean,
My question is:
Is crossing over in prophase 1 required for independent assortment ('of sister chromatids') in metaphase 2 to lead to further variation amongst gametes?
As my understanding is that if these sister chromatids being split apart were still genetically identical (i.e. no recombinant DNA formed from successful crossing over) the outcomes of independent assortment of these sister chromatids would be the same regardless of whether which chromatids moves to which equator. Hence I assume there is no further variation produced from this stage.
As well as, if successful crossing over occurs and after these homologous chromosomes separate from their bivalent, are these chromatids on the same chromosome considered sister chromatids still, despite no longer being genetically identical to one another?
Please do correct me where you best see fit and if possible cite a source. Thank you
My question is:
Is crossing over in prophase 1 required for independent assortment ('of sister chromatids') in metaphase 2 to lead to further variation amongst gametes?
As my understanding is that if these sister chromatids being split apart were still genetically identical (i.e. no recombinant DNA formed from successful crossing over) the outcomes of independent assortment of these sister chromatids would be the same regardless of whether which chromatids moves to which equator. Hence I assume there is no further variation produced from this stage.
As well as, if successful crossing over occurs and after these homologous chromosomes separate from their bivalent, are these chromatids on the same chromosome considered sister chromatids still, despite no longer being genetically identical to one another?
Please do correct me where you best see fit and if possible cite a source. Thank you
Reply 1
I do a level biology so I may be wrong with some parts. I think with your first question you may be right on that and the gametes would have the same diploid cells. However, since meiosis produces gametes, there would still be variation in sexual reproduction as both female and male wouldn’t have the same alleles in their gametes.
For your second question, they wouldn’t be sister chromatids. Sister chromatids means the chromatids genetically identical. They would be haploid chromosomes. You would also call them homologous chromosomes before they split as they might not have the same alleles (from crossing over).
https://biologydictionary.net/sister-chromatids/
https://www.diffen.com/difference/Diploid_vs_Haploid
For your second question, they wouldn’t be sister chromatids. Sister chromatids means the chromatids genetically identical. They would be haploid chromosomes. You would also call them homologous chromosomes before they split as they might not have the same alleles (from crossing over).
https://biologydictionary.net/sister-chromatids/
https://www.diffen.com/difference/Diploid_vs_Haploid
(edited 4 months ago)
Reply 2
Original post
by DragonfruitjuiceHi please may I have some help I am really confused and I am struggling to word this question for my teachers to understand what I mean,
My question is:
Is crossing over in prophase 1 required for independent assortment ('of sister chromatids') in metaphase 2 to lead to further variation amongst gametes?
As my understanding is that if these sister chromatids being split apart were still genetically identical (i.e. no recombinant DNA formed from successful crossing over) the outcomes of independent assortment of these sister chromatids would be the same regardless of whether which chromatids moves to which equator. Hence I assume there is no further variation produced from this stage.
As well as, if successful crossing over occurs and after these homologous chromosomes separate from their bivalent, are these chromatids on the same chromosome considered sister chromatids still, despite no longer being genetically identical to one another?
Please do correct me where you best see fit and if possible cite a source. Thank you
My question is:
Is crossing over in prophase 1 required for independent assortment ('of sister chromatids') in metaphase 2 to lead to further variation amongst gametes?
As my understanding is that if these sister chromatids being split apart were still genetically identical (i.e. no recombinant DNA formed from successful crossing over) the outcomes of independent assortment of these sister chromatids would be the same regardless of whether which chromatids moves to which equator. Hence I assume there is no further variation produced from this stage.
As well as, if successful crossing over occurs and after these homologous chromosomes separate from their bivalent, are these chromatids on the same chromosome considered sister chromatids still, despite no longer being genetically identical to one another?
Please do correct me where you best see fit and if possible cite a source. Thank you
Yes, if independent assortment didn’t occur then the chromatids pulled to opposite sides in metaphase 2 would the identical so no additional variation would be created. This is not likely to come up in an exam question but it is interesting to think about! Can’t seem to find an article on this specifically but you can easily draw it out on paper to come to this conclusion 🙂
Yes i think they are still considered sister chromatids as they are still joined at the centromere. Correct me if i have misunderstood your question
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