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It is not essentially asexual reproduction that causes mutations. Mutations can be caused because of errors in DNA replication which can happen during both mitosis and meiosis. Mutations can also be caused because of error-prone DNA repair mechanism. Other than these intrinsic factors there are physical and chemical mutagens that alter the DNA or ...


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As stated here the first sexual reproduction seems to be isogamy, which's purpose was likely to repair the DNA, as a damaged cell could repair its' (DNA) strands via recombination with a "healthy" one. As for lineages, the only thing I could find was also in this book at the very beginning, but there doesn't seem to be a difference as for which is the most ...


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The two distinct types you have mentioned in your question (determinate/indeterminate cleavage) are actually called autonomous specification and conditional specification, respectively. In the case of the former one, if we were to remove a blastomere, it would still produce the previously determined type of cells, while in the case of conditional ...


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Would something like CRISPR fit your criteria? CRISPR is essentially an adaptive immune system for bacteria. When a bacteria encounters foreign DNA (usually from an invading bacteriophage), it can cut it up and insert part of it in between palindromic repeats called CRISPRs. This small piece of DNA can be transcribed and then used as a template to recognize ...


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In multicellular organisms there are specialised cells called gametes that are responsible for sexual reproduction (sperm/ egg cells). Mutations occurring in these cells can be passed on to offspring (germ line mutations). Mutations occurring in others cells affect only the given individual (somatic mutations). Edit: For unicellular organisms it is pretty ...


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@Dhurba Benerjee I'm answering your question to my comment here because I need to include a diagram. As I said before ovum at the time of ovulation is arrested at the metaphase (M phase in cell cycle) 2nd meiotic division. This arrest is caused by the presence of two types of cytoplasmic activity 1. MPF - maturation promoting factor 2. CSF - Cytostatic ...


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So most cells require growth factors and survival factors to stay alive in an organism. Cells which stop receiving survival factors, such as sperm, undergo a process of programmed cell death (PCD) called apoptosis. Some cells will also undergo necrosis, or autophagy, among other types of PCD. Lachaud et al. performed a study in 2004 on the contribution of ...


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As stated in the answer by @CDB states these polar bodies doesn't last too long, and the second polar body which forms as the result of meiosis II, extrude only "after" fertilisation. The secondary oocyte is arrested in metaphase II until it becomes fertilised, so meiosis II can only by completed after ovulation and fertilisation (see e.g. UNSW Embryology: ...


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Polar bodies will usually undergo apoptosis in about 17 to 24 hours after the egg forms (the final stages of telophase II (cytokinesis)) because they have relatively little cytoplasm and shunted organelle development.



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