How Are Meiosis and Mitosis Similar Apex
Did y’all know that right now, inside your body, some of your cells are making copies of themselves? Don’t worry—that’s normal. Your cells demand to make copies of themselves so that they can replace one-time, dead cells. It’s the circle of life, Simba.
Somatic cells—that is, the cells in your trunk that aren’t sexual practice cells—do this via a process chosen mitosis. New sex cells, or gametes, are produced via a different process, called meiosis. Today, we’re going to talk well-nigh both of these. How are they different? How are they similar? Go on reading and y’all’ll find out!
The Prison cell Cycle and Mitosis: You Are Your Own Clone Army
Just like us multicellular organisms, cells have a cycle of life.
The cell cycle. Epitome from A&P half dozen.
Most of a cell’south time is spent in Interphase, the largest department of the pie-nautical chart-looking graphic above. Simply in that location comes a time in nigh cells’ lives when they’ve got to reproduce. In the S stage, the prison cell prepares for this by creating copies of all its DNA. (You tin read more about replication here.) Then, in Gii, the jail cell continues growing and preparing for mitosis. Nosotros’ll save G1
There are four phases of mitosis: prophase, metaphase, anaphase, and telophase. I’m sure at that place are lots of mnemonic devices out in that location for memorizing them, simply the one my seventh-grade scientific discipline instructor taught me is the 1 I’ve remembered to this day: “Paul Meets Anne Tonight.” Feel gratuitous to apply something more exciting, like “Poisonous Mushrooms Aren’t Tasty.”
Cheque out this overview of mitosis, featuring the mitosis 3D model in Visible Biology!
During prophase, the DNA that’due south floating around in the nucleus of the cell similar a hulk of tiny spaghetti starts to condense, coiling itself up super tight. Think that each of your 46 chromosomes (that is, distinct strings of Deoxyribonucleic acid) has a “double” because the jail cell’s DNA copied itself back in the South phase. Together, each chromosome and its double form a chromosome made up of two sister chromatids joined by a centromere. (This is what we typically picture when we think of a chromosome.)
A few more than things besides happen during prophase: the nuclear envelope that separates the nucleus from the rest of the cell dissolves, the nucleolus disappears, and structures called centrosomes migrate to each end of the cell. The centrioles within the centrosomes sprout spindle fibers (microtubules) as they go. Some spindle fibers grab onto centrosomes as this is going on.
Chromatin condensing, centrosomes moving to contrary ends of the cell, and spindle fibers grabbing on to sis chromatids. Video footage from Visible Biology.
Later that, it’due south time for metaphase. During metaphase, the chromosomes line up in the middle of the cell, and the microtubules form a full mitotic spindle beyond the prison cell.
In anaphase, the chromosomes in the center of the cell pull apart at their centromeres, and one sister chromatid from each one ends upwards at each cease of the jail cell.
Sister chromatids pulling autonomously. Video footage from Visible Biology.
Telophase is the final phase of mitosis, and this is when the official segmentation of one cell into two happens. First, the chromosomes relax back into chromatin and a nuclear envelope forms around each chromatin blob, making information technology into a brand new nucleus. A nucleolus appears in each of these new nuclei during telophase equally well, and the mitotic spindle, having served its purpose, is disassembled.
Telophase and cytokinesis.
Video footage from Visible Biology.
Finally, the heart of the cell pinches inwards and the ii nuclei motility away from each other, separating the original parent cell into ii girl cells. Each of these daughter cells is a diploid jail cell with 46 chromosomes (now with simply ane chromatid each), only like the parent cell and all the other somatic cells in the human body. They’re as well genetically identical to each other—so yes, they’re technically clones, simply that’southward a good affair for somatic cells.
The daughter cells are now in G1, during which they grow, synthesize proteins, and build organelles. Later that, they can either enter G0, the non-replicative phase, or move on to the Southward phase and go ready to reproduce. They grow upward and then fast, don’t they?
Meiosis: Half the Chromosomes, Double the Fun
Meiosis is similar to mitosis in many ways, merely in that location are a couple of important differences. Get-go of all, fifty-fifty though meiosis starts with a diploid cell (a primary oocyte or primary spermatocyte), its end products are 4 haploid girl cells, each with 23 chromosomes. Instead of being clones of the original prison cell, each of these daughter cells is genetically unique from its parent and its fellow girl cells.
Check out this overview of meiosis, featuring the meiosis I and Ii 3D models inVisible Biological science!
Meiosis consists of 2 rounds of division: meiosis I and meiosis II. Each round has a prophase, metaphase, anaphase, and telophase.
Meiosis vs. mitosis. Image from A&P 6.
Prophase I is, in my stance, the coolest phase of meiosis. The 46 chromosomes in your body’s diploid cells are organized into 23 homologous pairs. Ane chromosome in each of these pairs is from your mom, and the other one is from your dad. Prophase in mitosis and prophase I of meiosis both commencement out with double this genetic textile—that is, each of the 46 chromosomes has ii sister chromatids.
The homologous pairs of chromosomes detect and line up adjacent to each other, and then something amazing happens: recombination. Recombination (aka “crossing over”) is the process that makes prophase I so special. Information technology’south essentially a scrambling-around of genetic material that introduces some variation into the eventual girl cells. Recombination is 1 of the hallmarks of sexual reproduction, giving evolution a hand through irresolute things upwards on the genetic level.
Let’south look at a single homologous pair equally an example of how recombination works.
You’ve got your two chromosomes in the homologous pair—one from mom, and one from dad—and at the outset of prophase I, each ane of these has two chromatids. Together, the two chromosomes form a tetrad, named so because it has four chromatids total. Within the tetrad, the chromatids of the maternal and paternal chromosomes swap homologous sections of DNA with 1 another. (I will never forget how my high school biology teacher represented this process with a wacky, arm-waving dance.)
Crossing over in progress. Image from Visible Biology.
Fun fact! In the sex chromosomes of biologically male individuals (XY), crossing over tin can occur merely between sure regions of the X and Y chromosomes.
Later prophase I comes metaphase I, in which each of the tetrads line upwards at the center of the prison cell. So, in anaphase I, the two chromosomes of the tetrad are pulled abroad from one another, meaning that i chromosome from the tetrad ends up on each side of the cell. Note that the chromatids in each chromosome don’t divide from one another, as they would in mitosis.
Telophase I proceeds much every bit it does in mitosis, resulting in two daughter cells. Yet, these daughter cells are considered haploid, because each of them but has 23 chromosomes (one fix). In other words, each girl cell has only one chromosome from each homologous pair. It is important to note, however, that each of those 23 chromosomes still has two chromatids.
The finish result of meiosis I. Prototype from Visible Biological science.
This becomes important because the issue of the 2d half of meiosis is four haploid cells in which each chromosome only has one chromatid.
Meiosis II is a lot like mitosis.
Whereas prophase I starts with duplicated genetic material, prophase Ii starts with the results of telophase I—23 chromosomes with two chromatids each. These chromosomes line upward at the center of the cell in metaphase II and the chromatids are pulled apart from i some other at the centromere in anaphase II, just similar in regular mitosis.
Sister chromatids pulling apart in meiosis Two. Paradigm from Visible Biology.
Then, telophase II results in a total of four haploid girl cells (ii from each of the daughter cells produced in meiosis I), each with 23 single-chromatid chromosomes.
The end issue of meiosis Two: four haploid daughter cells. Prototype from Visible Biological science.
Here’s another fun fact, this time virtually female person gametes. Fifty-fifty though each master oocyte technically produces three or four daughter cells, just one of them is really a viable egg. The other two or three are chosen polar bodies, and they tin can’t be used in baby-making.
That was a lot of data I just threw at you, so let’s summarize the chief differences between mitosis and meiosis in chart form.
A diploid somatic cell
A diploid primary oocyte or spermatocyte
Two diploid somatic cells, genetically identical to each other and to the parent cell.
4 haploid gametes, genetically dissimilar from each other and from the primary oocyte or spermatocyte.
And that’s mitosis and meiosis in a nutshell! If you desire to learn more than about cells, check out these related VB Blog posts:
- Beefcake & Physiology: Parts of a Human Jail cell
- Tiny Transportation: Passive vs. Agile Transport in Cells
- Deoxyribonucleic acid and RNA Basics: Replication, Transcription, and Translation
Nosotros’ve also got a gratuitous eBook detailing the different organelles within homo cells!
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- Crash Course Biology #12: Mitosis: Splitting Upwards is Complicated
- Crash Course Biology #13 Meiosis: Where the Sex Starts
- Khan Academy: Mitosis | Cells | MCAT
- Saladin, K. Anatomy & Physiology: The Unity of Grade and Function. 7th ed.
How Are Meiosis and Mitosis Similar Apex