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Questions tagged [meiosis]

Division of a diploid cell to produce four haploid cells for the purposes of reproduction.

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What determines whether a cell divides by Mitosis or Meiosis?

What I learn from biology class is that mitosis is for producing somatic cells in animals and the gametes of some plants. And meiosis is for production of animal's gametes. I am curious about what ...
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Could multiplexed CRISPR disable the mitotic and meiotic genes of cancerous cells?

Although I believe there is a good reason -- or reasons -- why this theory, that CRISPR could disable the genes for division in cancerous cells, is incorrect, I haven't been able to find them. In ...
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How frequently does recombination occur, and how long are the recombinated fragments?

I understand the mechanics of recombination, but am struggling with the 'scale'. When two homologous chromosomes pair, roughly how many recombination events occur on average? I understand there will ...
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Can hybrids from closely related species with similar chromosomes reproduce?

Let's say the plant Triticum monococcum which has 2 sets of 7 chromosomes when diploid and 1 set of 7 chromosomes when haploid has the genome AA. When interbred with a different species that has the ...
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Considering Two Genes, Are There Only Two Possible Outcomes for the Four Gametes Produced After Meiosis, Regardless of Independent Assortment?

Is it true that for a single meiotic event when considering only two genes, there are only two possible genetic outcomes among the four gametes produced, regardless of whether the two genes are found ...
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Why is There a Necessity for Two Rounds of Cell Division and Four Daughter Cells in Meiosis

Why does meiosis involve two rounds of cell division instead of stopping after meiosis I, where each daughter cell would have one chromosome randomly selected from each pair of homologous chromosomes? ...
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What's the significance of DNA replication (S phase) before Meiosis?

From what I'm able to understand, Meiosis should end up with haploid cells with chromosomes having single chromatids (I don't know why it's necessary, but alright) I understand that meiosis has a ...
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What makes protein binding to the DNA random?

We know that the genetic recombination process in known as a random process. On the other hand, it has also been discovered that certain proteins (such as PRDM9) determine what recombination hotspots ...
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How random is genetic recombination?

Two parents can have a very large number of different potential offsprings, and it's common knowledge that the daughter chromosomes in meiosis are produced randomly, i.e. in crossover, the exact spots ...
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If crossing over did not occur, would pairs of cells after meiosis II have the same genes?

If crossing over did not occur, would there be two pairs of cells with the same chromosomes after meiosis II? This question came to my mind while I was reading through my bio textbook. After meiosis I,...
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What does this statement pertaining to fission mean?

I was reading about fission on Wikipedia when I encountered the following statement under Fission of prokaryotes section. Like in mitosis (and unlike in meiosis), the parental identity is lost. What ...
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Why does Meiosis produce 4 daughter cells instead of 2? Won't splitting the initial diploid cell into two haploid cells be easier?

At first, I thought it was because of crossing-over, but when I thought more about it, that didn't seem reasonable. Why don't cells just do meiosis like this? (I know that we don't understand all the ...
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How is RNA content distributed in daughter cells during cell division?

During cell division, DNA becomes equally distributed between the daughter cells. But how is RNA content distributed in the daughter cells?
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At what point in evolution is a new species identified? [duplicate]

As we know, a change in allelic frequency leads to evolution, and as these changes accumulate a new species is created. My question has two parts - A classical definition of species which is now not ...
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By selecting sex cells after meiosis, would it be possible to create two offspring with inverse parental DNA of one another? [closed]

Would it theoretically be possible to select two sex cells after a male meiosis (filtering out the two where crossover had taken place) and combine each with two sex from a female meiosis (imagining ...
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Why do nearby cells have similar meiosis periods?

A few days ago, I conducted an experiment to observe the meiosis of rye ears. During the experiment, I observed that cells in similar locations have similar meiosis period. Can anybody tell me why ...
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How do gene locations change during crossing over events?

Suppose you have two variants from the same species, which have slightly different chromosomes I's to each other. Genes may be in slightly different positions on the chromosome, and the lengths of the ...
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How could a cell only have chromosomes from father or from mother? [closed]

How could arrangement one even be possible? How could a cell only have chromosomes from father or from mother? [Image modified from "The laws of inheritance: Figure 5," by OpenStax College, ...
HypnoticBuggyWraithVirileBevy's user avatar
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When is it better for a gene to cause a biased sex ratio?

Because genes are selfish and want to maximise their transmission from generation to generation, if they can distort a population's sex ratio, isn't it always in their interest to cause a biased sex ...
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When the sister chromatids are joined in the centromere, why is it stated that the number of chromosomes is 46 and not 72?

Before the DNA is replicated in a human somatic cell, the cell has 46 chromosomes. Also, after the sister chromatids are separated during Anaphase, the chromosome number in the cell doubles to 72, so ...
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Is the cell cycle applicable to meiosis as well, or just mitosis?

All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis). Is there an equivalent "...
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Chiasmata and Adaptation

We know that during the crossing over of meiosis II, some portions of the paternal chromosome recombine with the maternal chromosome along the chiasmata. And the number of chiasmata varies. My ...
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Germ cells vs. gametes

Naively, I thought that germ cells are diploid (in diploid species like human/mouse at least). Then, germ cells undergo meiosis and become haploid. I thought this was the critical change that defined ...
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Which chromosome of the two contained in a haploid cell goes into the diploid cell after fertilisation?

I am totally new to biology and I have a very stupid question. In the typical representation of meiosis, haploid cells contain two different chromosomes, resulting from the crossing-over process. But ...
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How many of the four meiotic daughter chromosomes of a homologous pair can be recombinant via crossover?

In graphics I've seen, crossing over occurs between the "inner" two chromatids in a side-by-side arrangement of two duplicated chromosomes: This suggests that only two of the four meiotic daughter ...
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Why are the products of Meiosis 2 different?

In Meiosis I, 46 chromosomes crossover. These mixed chromosomes then split off into new cells. In these new cells, Meiosis II occurs, where these mixed chromosomes have their chromatids ripped apart. ...
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How can paternal chromosomes be present in an egg cell during meiosis I or crossing over, if fertilisation has not yet occurred?

I am very confused about crossing over. It is said that crossing over increases genetic variation as it is a combination of paternal and maternal chromosomes. However, crossing over occurs in meiosis ...
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Human somatic cells have 22 pairs of homologous chromosomes?

I am studying for my Bio class and I am stuck with questions that I came up with during this chapter of Meiosis. I understand that human somatic cell is made up of 22 pairs of autosomes and 1 pair of ...
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What is the probability that a gamete will only contain father's chromosomes

As it is depicted in most textbooks, cross-over does not occur between the two "outer" sister chromatids. By independent assortment during Meiosis I, there is 1/2^23 chance that all father's ...
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Can men with Klinefelter syndrome produce chromosomally normal sperm?

Individuals with Klinefelter syndrome are XXY. Even though sperm counts are low some individuals can generate enough to be used in IVF and have offspring. Does this mean that when sperm are formed, ...
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Meiotic recombination hotspots

Im trying to find a proper and general file with chromosomal coordinates for meiotic recombination hotspots. I know that ucsc hgtables, has a table with recombination regions and their recombination ...
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My understanding of chromosomes and the processes related to them is lacking [closed]

I'm sorry for the incredibly simple question, I just can't seem to find any answers elsewhere online. I am a high school student currently studying for the upcoming AP biology exam, and recently I ...
scripturient's user avatar
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Possible combinations in the Meiosis' Telophase 1

As you might already know Meiosis is the process in eukaryotic, sexually-reproducing animals that reduces the number of chromosomes in a cell before reproduction $^{[1]}$ One of the reasons why ...
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Does the law of independent assortment apply to homologous chromosomes or alleles, or both?

My textbook is giving me two definitions 1st def: "random orientation of homologous chromosomes at the metaphase plate in meiosis 1." 2nd def: "alleles for one gene separate into gametes ...
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Is there random assortment in metaphase II?

First, a little notation. Call a the first chromosome from my mother and A its homologous partner from my father. ...
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Fertilization of the human egg- where does our centrosome come from? [closed]

Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can ...
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When in the cell cycle is the number of chromosomes normally reduced?

Page 96 of the Study Guide for Campbell Biology, 11th Edition has the following question: A reduction in the number of chromosomes per cell occurs a. During meiosis I b. During meiosis ...
freeradical's user avatar
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Which is the correct term haploid daughter cells or haploid parent cells?

Meiosis 2 begins with 2 haploid parent cells and ends with 4 haploid daughter cells (gametes). Gametes from the opposite sex can now merge together and fertilize. If I were to refer to a specific ...
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Do chromosomes line up as pairs in mitosis or meiosis?

Here is a question from the book SAT II Success Biology E/M (where the SAT is the exam taken by the American high school students): Homologous chromosomes line up in pairs in (A) metaphase of ...
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What confuses me about "homologous gene"

When I first encountered homologous genes I thought those genes are identical because the text book said so, and "homologous" meant the same knowledge. But as I studied along, it comes out that ...
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During what phase is the cell polyploid? [closed]

During what phase is the cell polyploid? Why is it polyploid at this point--what has happened to create this state and why is it important to the process?
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How long does each of the stages in meiosis take?

For each stages of meiosis (i.e. Interphase, Prophase I, ...), I wanted to know the time between each stages either in percentages or minutes. However, while I could find the cell cycle for mitosis ...
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What exactly happens during the crossover [closed]

My knowledge of biology is rather limited, but I think I have a grasp of some basic concepts. For me (as a person close to math) a chromosome is a sequence of elements from the set {A,C,T,G} of some (...
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Human ancestor reproduction after chromosome fusion

I read somewhere that human chromosome 2 is the result of 2 primate chromosomes fusing together somewhere along our evolutionary journey. This is why we have 23 chromosomes while other primates have ...
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What does the nucleus look like in S phase of Meiosis?

I was watching an animation video about Meiosis and this is what the video shows (pics attached.) It shows that before synthesis, each chromosome exists as single chromatid and then after replication,...
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Polyploidy, or why plants of different species can produce fertile offspring hybrids more frequently than animals?

This site says: Plants hybridize much more frequently and successfully than animals do. [...] Chromosomal doubling (polyploidy) occurs more frequently in plants and facilitates the fertility of the ...
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DNA replication during Mitosis

I am a bit confused. During Meiosis, DNA is replicated to form a cell with half the DNA and likely to have variations. But since the replication process of meiosis and mitosis are the same, why do DNA ...
Paritosh's user avatar
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How would homologous recombination and mutations affect speciation?

I'm wondering how homologous recombination and mutations can affect how speciation can occur from one species (so that 2 will be created). I'm doing research and I found that different mutations and ...
DeepLearner's user avatar
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How do biologists determine the parents of a child

I am not well-versed in biology so this question might be wrong. As far as I understand meiosis, two germ line cells with 23 chromosomes each (one cell from the father and another from the mother) ...
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Can you use a cell in meiosis to create a karyotype?

Why might it be problematic to use a cell undergoing meiosis to create a karyotype?
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