dancer5678
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Are sperm and egg cells the product of mitosis or meiosis? When I am told meiosis happens in gametes, does that mean that the egg and sperm cells separately divide by meiosis, or that after they fuse, they then divided by meiosis as one?

I hope that makes sense, what I’m saying isn’t very difficult to type.
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Reality Check
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(Original post by dancer5678)
Are sperm and egg cells the product of mitosis or meiosis? When I am told meiosis happens in gametes, does that mean that the egg and sperm cells separately divide by meiosis, or that after they fuse, they then divided by meiosis as one?

I hope that makes sense, what I’m saying isn’t very difficult to type.
Gametes (sperm and egg) are formed by meiosis. You need to understand why this is the case, from a genetic material point of view. Your question indicates that you're very confused between mitosis and meiosis, so I suggest you urgently revise this topic from your textbook/teacher. Basically, you need to very clearly understand why a gamete is formed by meiosis, but a fertilized egg grows by mitotic division.
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dancer5678
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I have always understood them until today. I was revising and the revision guide says that the parent cell that divides during meiosis is diploid, and has inherited half of it’s chromosomes from it’s mother and half from its father. I understand that egg gametes are haploid, in order to fuse and make a diploid cell during fertilisation, so what type of cell is the diploid parent cell at the start of meiosis? If gametes are haploid then why is this diploid ?
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Reality Check
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(Original post by dancer5678)
I have always understood them until today. I was revising and the revision guide says that the parent cell that divides during meiosis is diploid, and has inherited half of it’s chromosomes from it’s mother and half from its father. I understand that egg gametes are haploid, in order to fuse and make a diploid cell during fertilisation, so what type of cell is the diploid parent cell at the start of meiosis? If gametes are haploid then why is this diploid ?
I think you're forgetting that there is Meiosis I and Meiosis II...
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dancer5678
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(Original post by Reality Check)
I think you're forgetting that there is Meiosis I and Meiosis II...
I’m only at gcse level and we only learn one version of meiosis
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Nour M.
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(Original post by dancer5678)
I have always understood them until today. I was revising and the revision guide says that the parent cell that divides during meiosis is diploid, and has inherited half of it’s chromosomes from it’s mother and half from its father. I understand that egg gametes are haploid, in order to fuse and make a diploid cell during fertilisation, so what type of cell is the diploid parent cell at the start of meiosis? If gametes are haploid then why is this diploid ?
I think you got the processes of meiosis and mitosis mixed up. The cells at the beginning of both mitosis and meiosis have to logically be diploid, as mitosis forms duplicate copies which are also diploid, and meiosis produces 4 haploid cells per each diploid cell. The haploid cells are what we call gametes. Now the reason they are haploid is because of how the diploid cell divided at the beginning. So for instance, humans have 46 chromosomes right? They are arranged in 23 homologous pairs, with one chromosome in each pair being from the father, while the other is from the mother. During meiosis, each of these chromosomes divides and turns into two smaller "chromatids", which are genetically identical to the chromosome at the beginning and joined together at one point. So basically you'll have about 46*2= 92 chromatids at the end of the that (for the sake of simplicity, I'll keep calling them chromosomes but keep in mind that each "chromosome" is two joined chromatids now). This is then followed by the chromosomes lining in the middle of the cell, with each chromosome in every homologous pair lined opposite to each other (basically that means you'll have two lines in the middle). Each chromosome is pulled to one end of the cell, followed by the cell pinching off at the middle. The cell has now separated into two cells with 46 chromatids each (there are 46/2= 23 chromosomes present). However, they have different chromosomes cause, if you remember, each chromosome in a homologous pair is either from the father or mother. The chromosomes now in each of these two cells line up in a single file and each of the chromatids of every "chromosome" is pulled to the opposite side. During this, parts of the chromatids my break off and attach to the other chromatids; this is what gives variation. The cells pinch off once more and divide each into two more cells. So in the end, you'll end up with 4 cells each with 23 chromatids (haploid). Fyi you don't need to know all of this for GCSE, it's just to help you understand why the diploid cell at the beginning can form haploid cells. Hope I was able to clarify
Last edited by Nour M.; 2 years ago
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dancer5678
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Thank you!
(Original post by Nour M.)
I think you got the processes of meiosis and mitosis mixed up. The cells at the beginning of both mitosis and meiosis have to logically be diploid, as mitosis forms duplicate copies which are also diploid, and meiosis produces 4 haploid cells per each diploid cell. The haploid cells are what we call gametes. Now the reason they are haploid is because of how the diploid cell divided at the beginning. So for instance, humans have 46 chromosomes right? They are arranged in 23 homologous pairs, with one chromosome in each pair being from the father, while the other is from the mother. During meiosis, each of these chromosomes divides and turns into two smaller "chromatids", which are genetically identical to the chromosome at the beginning and joined together at one point. So basically you'll have about 46*2= 92 chromatids at the end of the that (for the sake of simplicity, I'll keep calling them chromosomes but keep in mind that each "chromosome" is two joined chromatids now). This is then followed by the chromosomes lining in the middle of the cell, with each chromosome in every homologous pair lined opposite to each other (basically that means you'll have two lines in the middle). Each chromosome is pulled to one end of the cell, followed by the cell pinching off at the middle. The cell has now separated into two cells with 46 chromatids each (there are 46/2= 23 chromosomes present). However, they have different chromosomes cause, if you remember, each chromosome in a homologous pair is either from the father or mother. The chromosomes now in each of these two cells line up in a single file and each of the chromatids of every "chromosome" is pulled to the opposite side. During this, parts of the chromatids my break off and attach to the other chromatids; this is what gives variation. The cells pinch off once more and divide each into two more cells. So in the end, you'll end up with 4 cells each with 23 chromatids (haploid). Fyi you don't need to know all of this for GCSE, it's just to help you understand why the diploid cell at the beginning can form haploid cells. Hope I was able to clarify
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tocka90
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Look at https://www.youtube.com/channel/UCQX...AnOAPVBv-QRNTQ for revision topics, model answers and exam tips
(Original post by dancer5678)
Are sperm and egg cells the product of mitosis or meiosis? When I am told meiosis happens in gametes, does that mean that the egg and sperm cells separately divide by meiosis, or that after they fuse, they then divided by meiosis as one?

I hope that makes sense, what I’m saying isn’t very difficult to type.
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Nour M.
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:five:
(Original post by dancer5678)
Thank you!
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