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Meiosis vs. Mitosis


Meiosis is a type of cell division that reduces the chromosome number from 2n to n to make gametes viable for reproduction in humans. I know that during meiosis, there is independent assortment and crossing over that occurs, which help to make more genetically individual organisms.

My question is, why don't haploid gametes go through mitosis to reproduce instead of diploid germ cells going through meiosis to create more gametes, without considering crossing over and independent assortment? This is just my opinion, but meiosis seems like a much more energy intensive process. After the germ cells go through meiosis once to create the gametes, I do not see why the gametes don't then just multiply via mitosis (again, not considering crossing over/independent assortment.)

Is there any specific reason, other than to create more genetically diverse people, that gametes do not undergo mitosis to multiply rather than germ cells undergoing meiosis to make more gametes?

Sorry if my question is confusing, I'm just curious to what the reason is. It's probably something obvious I'm not seeing myself. :)


Couldn't fit in a comment…

To me, your question sounds like "what are the possible advantages of sexual reproduction over asexual reproduction?" but in the meantime you're saying that you're not interested neither in the advantage of recombination nor in the advantage of "independent assortment". I don't quite see what you mean by "independent assortment" in this context.

I just want to say some words about some "proximate" possible explanations of the evolution of sex. It's been suggested that meiosis have evolved in order to repair damage in double stranded DNA. Also, it's been suggested that meiosis is important for the problems of telomere length also.

You might be interested to have a look to the evolution of bi-phasic life cycles and, more globally speaking to the evolution of sex.


I would suggest that the key here really is the variation produced from meiosis. Every gamete produced from meiosis is genetically unique. This gave rise to variation, which is the raw material for evolution. Meiosis would give a selective advantage in this way, therefore it could have allowed organisms to survive and pass on their genes.


Mitosis vs. Meiosis

Both mitosis and meiosis result in eukaryotic cell division. The primary difference between these divisions is the differing goals of each process. The goal of mitosis is to produce two daughter cells that are genetically identical to the parent cell. Mitosis happens when you grow. You want all your new cells to have the same DNA as the previous cells. The goal of meiosis is to produce sperm or eggs, also known as gametes. The resulting gametes are not genetically identical to the parent cell. Gametes are haploid cells, with only half the DNA present in the diploid parent cell. This is necessary so that when a sperm and an egg combine at fertilization, the resulting zygote has the correct amount of DNA&mdashnot twice as much as the parents. The zygote then begins to divide through mitosis.

Table (PageIndex<1>): comparison of mitosis and meiosis
Mitosis Meiosis
Purpose To produce new cells To produce gametes
Number of Cells Produced 2 4
Rounds of Cell Division 1 2
Haploid or Diploid Diploid Haploid
Are daughter cells identical to parent cells? Yes No
Are daughter cells identical to each other? Yes No

Figure (PageIndex<2>) shows a comparison of mitosis, meiosis, and binary fission.

  • Binary fission occurs in bacterial. Note that bacterial cells have a single loop of DNA. The DNA of the cell is replicated. Each loop of DNA moves to the opposite side of the cell and the cell splits in half.
  • Mitosis and Meiosis both occur in eukaryotic cells. In the example below the cell has 4 total chromosomes. These are replicated during the S phase.
    • In mitosis, the chromosomes line up in the center of the cell. Then, sister chromatids separate and move to the opposite poles of the cell. The cell divides, producing two cells with 4 total chromosomes
    • In meiosis, the homologous chromosomes line up in the center of the cell. Then each chromosome moves to opposite poles and the cell divides.
      • Next, the chromosomes line up in the center of the cell. Then, sister chromatids separate and move to the opposite poles of the cell. This produces four cells with 2 chromosomes each. These are the gametes.
      • Two gametes combine to form a zygote with 4 total chromosomes.

      Figure (PageIndex<2>): A comparison between binary fission, mitosis, and meiosis.


      Mitosis Vs Meiosis

      #1. Definition: Mitosis Vs Meiosis

      Mitosis is part of cell division, where the chromosomes inside the nucleus are split into 2 sets of identical chromosomes, and each has a nucleus.

      While Meiosis is a cell division that reduces the number of chromosomes in half. This process occurs in every se**xual reproduction.

      #2. Inventors: Mitosis Vs Meiosis

      Mitosis was discovered by Walther Flemming, who is an anatomist, while meiosis was discovered by Oscar Hertwig who is a biologist, both of whom are both from Germany.

      #3. Stages of Cell Division: Mitosis Vs Meiosis

      Mitosis consists of stages of prophase, metaphase, anaphase, telophase, and cytokinesis. While meiosis consist of the longer stages, namely prophase I, metaphase I, anaphase I, telophase I, prophase II, metaphase II, anaphase II, and telophase.

      #4. Cell Division

      In mitosis, somatic cells only once divide at the cytokinesis stage, while in meiosis the genital cells divide twice at the telophase I and II stages.

      #5. Where Mitosis and Meiosis Cleavage Occurred

      Mitosis cleavage in animals occurs in cells of the body (somatic) and if in plants where it occurs in meristem tissue (always active tissues hold cell division). For example, at the end of the stem, the root, and in the cambium.

      While the division of meiosis in animals occurs in the reproductive organs of the genital cells (gonads) and if meiosis in plants occurs in stamens and pistils.

      #6. Caryokinesis and Cytokinesis

      Caryokinesis is the division of cell nucleus matter that occurs during cell division. In mitosis, caryokinesis occurs during Interphase. While in meiosis occurs during interphase I.

      Cytokinesis is the division of cytoplasm that occurs during cell division. In mitosis, cytokinesis occurs at the end of the telophase stage. Then in meiosis occurs twice, namely at the end of telophase I and telophase II.

      #7. Function

      Mitosis usually occurs for cell reproduction and also for the growth and repair of cells in the body of an organism or living being.

      Meanwhile, meiosis itself occurs to distinguish the genetics of an organism through se**xual reproduction.

      #8. Reproduction Type

      During cell division or reproduction in mitosis, the type of reproduction is ase**xual.

      Meanwhile, the reply of cell division or reproduction in meiosis is the division of cells with se**xual reproduction type.

      #9. Genetic

      Se**xual reproduction used in the meiosis process makes genetics slightly different from each other. In contrast to ase**xual reproduction that the child cells are identical to stem cells.

      Some mutations occur in the meiosis process. Genetic differences from one to another make living things more resistant and adapt to the environment, which increases the chances of surviving the organism to its offspring.

      #10. Organism

      All types of organisms, both micro and macro, will experience or go through the process of cell division by mitosis. While meiosis tend to be experienced by some living things such as humans, animals, plants, and also fungi.

      #11. Mitosis and Meiosis Results

      Mitosis cleavage will result in two daughter cells that have the same number of chromosomes as their parent (2n) called diploids.

      While in meiosis cleavage will produce four daughter cells that have half the number of stem cell chromosomes (n) called haploids.


      Mitosis vs. Meiosis: Key Differences, Chart and Venn Diagram

      In order for organisms to grow, cells have two options: they must either replicate themselves to create more cells, or the cells themselves must expand in volume. In humans, tissues such as the skin and blood contain cells that are actively dividing, whilst other tissues such as fat contain cells that expand (good if you need energy for winter, bad if you are trying to fit into some expensive jeans). Other cells, such as neurons, will never divide again once they are terminally differentiated they are post-mitotic.

      In the process of replicating themselves, cells have another choice: do they want to make an identical copy and be left with two cells? Or do they want to make four “half-copies”, in preparation for sexual reproduction, where their genetic content will be made whole again by the process of fertilisation? This choice is the choice between mitosis and meiosis.


      Hook - Introducing The Competitors

      Students will get out a sheet of paper and create a T-chart to list all of the characteristics of mitosis and meiosis. Students have had the opportunity to learn about both process in previous lessons: Mitosis Lesson and Meiosis Lesson.

      After two minutes the students will share their responses with their neighbor and are able to add to their list after their brief collaboration. This graphic organizer will help to provide highlights and inspiration for the students' essay later in the lesson.

      Students will watch this 3 minute video clip to review their understanding of mitosis and meiosis to add a little fun and a lot of knowledge about cell division:


      How I Teach Mitosis and Meiosis in High School Biology

      This post originally appeared on the blog Science With Mrs Lau.

      Learning about mitosis and meiosis in biology class can be challenging for students but I find it’s one of their favorites. Visual learners really thrive in this unit. Understanding how mitosis and meiosis work is essential for understanding independent assortment, genetics, and evolution so I spend a lot of time on this unit. I use a few different methods for helping students understand and really grasp the material.

      1. I show a lot of animations! Mitosis is dynamic. Chromosomes move! It’s really important for them to see the process in action. There are loads of great animations online for teachers and here are a bunch that I like to use.

      2. A teacher at a school I used to work at does a really cool project during this unit. She has student groups create stop motion animation videos of either mitosis or meiosis! Students are allowed to use any materials they want and the video has to have a minimum of 50 pictures (but more is way better!) When we co-taught a course, we required the regular level students create videos for mitosis and the honors level students created videos for meiosis. In each video, students had to have an identifying “token”, an item that they added into each picture/frame to show that they were the creators, to prevent video editing from stolen sources like Youtube or other online videos. Students really had fun with this and manipulating their materials to make the videos really helped them to cement the processes into memory. In this day and age, it’s actually quite easy for students with smart phones to create their own videos! Here is one of my favorite student videos: Lego Meiosis.


      3. I use diagrams and coloring activities to help students identify the components and understand how chromosomes in cells move throughout the mitosis or meiosis timeline. I used to download pictures online, but now I create my own! You can see these in my store. I have coloring activities, cut and paste activities, and short simplified readings all in one package for mitosis, meiosis, spermatogenesis/oogenesis, and crossing over.


      What techniques or resources do you like to use when teaching mitosis and meiosis? />

      I’m a high school science teacher taking a few years off of teaching to spend time with my 4 year old son and 7 month old daughter. I plan on going back to teaching and in the meantime, I create lessons that I always wished I had and plan on using in the future. I live in New Jersey, but our family loves to travel together and go on adventures. We lived in Hong Kong for 6 months (with a toddler!), and I can’t wait to go back to visit Asia and explore more of the other side of the world. I love genetics, and I studied at Massachusetts Institute of Technology before I realized teaching was my true calling. Social insects (outside my house) fascinate me and I want to be E.O. Wilson when I grow up. Visit my Instagram (@sciencemrslau) page or follow my blog to see my day-to-day adventures observing science with my kids. And check out my TeachersPayTeachers store to see the lessons I create. Here is a picture of me, carrying a sleeping toddler, by the beautiful fountain in Hong Kong Park.


      Anaphase I of Meiosis

      In Telophase I, the nuclear envelope reappears around each group of recombinant chromosomes, and during Cytokinesis I the cytoplasm divides.


      Mitosis

      The diagram shows Mitosis and celldivision as a cyclic process. Image Source: Wikimedia Commons

      The process of cellular mitosis occurs in four primary phases: prophase, metaphase, anaphase and telophase. A fifth “phase,” known as interphase, is the state in which a somatic cell spends most of its lifespan.

      Note: you will not need to know the names of these phases for the AP® Biology exam, but you will still be required to describe the steps.

      Take a look at how each of these phases breaks down.

      Interphase

      Not necessarily a true “phase” of mitosis, interphase is the normal, non-division state of somatic cells. If you throw a prepared slide of cells under a microscope, chances are the majority of them will be sitting in interphase, looking relatively inactive and uninteresting. If a cell is not in interphase, it is undergoing mitosis (which is sometimes referred to as “M phase”).

      Interphase itself is split into three stages, as follows:

      G1: cell simply grows

      S phase: cell continues growing, starts duplicating DNA

      G2: growth continues while cell prepares for mitotic division

      Prophase

      This is where the action begins. As a cell prepares to divide, it enters prophase, in which the nucleoli—spherical structures inside the nucleus that contain RNA and protein—disappear and the chromatin of the nucleus condenses into tightly-packaged chromosomes. Note that because the DNA was duplicated in S-Interphase, each chromosome now contains two copies of the cell’s DNA.

      The membrane that surrounds the genetic material of the cell (known as the nuclear envelope) then disappears, and a mitotic spindle is created as the microtubule organization centers (MTOCs) move toward opposite ends of the nucleus. These MTOCs are specialized structures that control the arrangement of a protein called tubulin into long microtubules that can manipulate the positioning of the cell’s genetic material. The mitotic spindle is simply the term for the overall structure of microtubules that guide this material.

      As the MTOCs move apart, the microtubules they’ve built increase in length and connect to the centromeres of the chromosomes via a region called the kinetochore. The MTOCs are then capable of moving the chromosomes toward or away from the poles of the cell by shortening or lengthening the microtubules.

      Metaphase

      During metaphase, the fully-formed chromosomes are aligned by the microtubules at the center of the cell in a plane known as the metaphase plate. Then, the attached microtubules retract, splitting each chromosome into its individual sister chromatids. These resulting chromatids still have a centromere each, however, and therefore are referred to as individual chromosomes from this point forward.

      Metaphase ends as soon as the original chromosomes are split.

      Top tip: to determine the number of chromosomes at any time during the process, simply count the number of centromeres.

      Anaphase

      After the initial separation of the chromosomes, the new chromosomes (the split chromatids) are pulled to the poles of the cell via the shortening of the microtubules. At the end of this phase, each pole contains a complete set of identical chromosomes.

      Since the DNA copies made during the S phase of interphase have now split, the chromosomes at the poles consist of single chromatids with only a single copy of the parent cell’s DNA.

      Telophase

      To wrap-up the division process, normal cell organelles start to re-build and the newly-formed daughter cells begin to take shape for their own interphase. Nuclear envelopes develop around the genetic material at each pole, the chromosomes unwind and return to loosely-floating chromatin, and the nucleoli appear once more.

      While the nucleus reforms, the dividing cell undergoes cytokinesis, which refers to the splitting of the unit and the division of cytoplasm across the two new cells. A cleavage furrow develops at the center of the dividing unit and cinches closed like a drawstring, leaving two separate cells with enclosed cell membranes.

      Final result: two diploid daughter cells containing identical genetic material to the parent cell.


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      Watch the video: Mitosis vs. Meiosis: Side by Side Comparison (January 2022).