Mitosis and meiosis

Pretty much everything alive - from a humble bacteria, to a baby blue whale, has two main goals - to grow and to reproduce. Our cells are no different. They grow and they reproduce. But the reproduction part can be done in two distinct ways - Whereas in These gametes can then pair with completely different gametes to form a cell that’s quite different from the parent cell. This newly formed cell can then do Most of the The first phase is called G1. During G1, the cell gets bigger in preparation for cell division. At this point the 46 chromosomes look like spaghetti and are called chromatin fibers. Each chromatin fiber is made of a single copy of the genetic material - called a chromatid. The second phase is the During The two chromatids are joined together in a region called the centromere - adding up to 92 chromatids total. The third phase is G2. During G2, the cell does some more growing before finally entering Some cells, like neurons, enter what’s called the G0 phase - where they basically continue to live but don’t divide. But most cells do enter Sitemap USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trad...

A regular human cell has 46 chromosomes: 44 autosomes, which come in pairs, and 2 sex chromosomes, which specify whether someone is male (usually XY) or female (usually XX). The pairs of autosomes are called "homologous chromosomes." Homologous chromosomes have all of the same genes arranged in the same order, but there are small differences in the DNA letters of the genes. When cells divide to make more cells (mitosis) or reproductive cells (meiosis), and when reproductive cells join to make a new individual (fertilization), it is important that the new cells get the proper number of chromosomes. Read on to learn more about these processes. Before a cell divides to make two cells, it copies all of its chromosomes. These copies, called sister chromatids, are identical. Until the cell divides, the identical copies stay connected with each other by their middles (centromeres.) When the cell divides, the copies are pulled apart, and each new cell gets one identical copy of each chromosome. This type of cell division is called mitosis, and it produces cells with a total of 46 chromosomes. Beginning soon after fertilization (see below), all of the cells in your body were made this way. Thus, every cell in your body has an identical set of chromosomes. When egg and sperm form, they go through a special type of cell division called meiosis. One purpose of meiosis is to reduce the number of chromosomes by half. The other is to create genetic diversity. Meiosis begins like mitosis:...

share How Cells Divide • By Rick Groleau • Posted 10.09.01 • NOVA Most of the time, when a cell in our bodies divides, each new cell carries a complete set of chromosomes. The cells involved with human reproduction, however, carry only half after division occurs. In this step-by-step explanation, learn about mitosis and meiosis, the two types of cell division. Explore the stages of two types of cell division, mitosis and meiosis, and how these processes compare to one another. This feature originally appeared on the site for the NOVA program Background on Meiosis and Mitosis As viewed from a human perspective, nature seems to have done ingenious engineering to overcome obstacles. Take the evolution of sex, for instance. To make the move from asexual to sexual reproduction, nature took a system by which parent cells reproduced simply by dividing (asexual reproduction) and altered it to allow two parent cells to combine to create offspring (sexual reproduction). Asexual reproduction relies on a process called mitosis, in which the nucleus of a cell divides to create two new nuclei, each containing an identical copy of DNA. Mitosis allows the cells in your body to divide and regenerate—your hair to grow, your skin to heal after being wounded. Almost all of the DNA duplication in your body is carried out through mitosis. Meiosis, on the other hand, is the process by which certain sex cells are created. If you're male, your body uses meiosis to create sperm cells; if you're fem...

CONTENTS • What is Meiosis? • Function of Meiosis • Phases of Meiosis • Phases of Meiosis I • Prophase I • Metaphase I • Anaphase I • Telophase I • Results of Meiosis I • Phases of Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II • Results of Meiosis II • Examples of Meiosis • Human Meiosis • Fruit Flies • Related Biology Terms • Quiz Index What is Meiosis? Meiosis is the process in eukaryotic, sexually-reproducing animals that reduces the number of chromosomes in a cell before reproduction. Many organisms package these cells into gametes, such as egg and sperm. The gametes can then meet, during reproduction, and fuse to create a new zygote. Because the number of alleles was reduced during meiosis, the combination of two gametes will yield a zygote with the same number of alleles as the parents. In diploid organisms, this is two copies of each gene. Function of Meiosis Meiosis is necessary for many sexually-reproducing animals to ensure the same number of chromosomes in the offspring as in the parents. The act of fertilization includes two cells fusing together to become a new zygote. If the number of alleles of each gene is not reduced to 1 in the gametes that produce the zygote, there will be 4 copies of each gene in the offspring. In many animals, this would lead to many developmental defects. In other organisms, polyploidy is common and they can exist with many copies of the same gene. However, if the organism cannot survive if they are polyploidy, ...

Getting mitosis and meiosis confused on a biology exam can cost you a lot of points, so it's important to keep these two cellular processes straight. In this guide, we break down mitosis vs meiosis, explain each of the processes, and lay out their similarities and differences so that you’ll be able to easily explain what each process does and how the two differ. What Is Mitosis? What Is Meiosis? Mitosis and meiosis are both processes of cell division. Organisms are constantly replenishing their cell supply and creating new cells to replace those that are old or damaged, as well as making cells to be used to create new organisms during sexual reproduction. Mitosis is when a cell divides to create two identical daughter cells. Mitosis occurs in somatic cells (all the cells that aren’t sex cells), and it’s a process critical for producing new cells and keeping the organism alive and healthy. Most cells in the human body only last a few days to a few weeks (an exception is brain cells, which typically last your whole life), so your body must constantly be making new cells through mitosis. All cells go through a process of formation, growth, division, and eventual death. During mitosis, the parent cell’s nucleus is split to form two sets of chromosomes for each of the new daughter cells. You can learn more about this process by reading Meiosis also involves cell division, however, it occurs in far fewer cells in your body. The only cells that go through meiosis are gametes, or ...

" " Mitosis is the division of a single cell into two cells (as shown here), each with its own nucleus and the same number and kind of chromosomes as the parent cell. Meiosis occurs when a single cell divides twice to produce four cells containing half the original amount of genetic information. Juhari Muhade/Getty Images In the beginning, you were just some As you're probably aware, in order to make "you", and not "half Paul and half Diane," some complicated genetic juju had to go down — the 23 chromosomes from each of your parents' gametes had to join forces to make your one-and-only genome (your complete set of DNA), which has been held in the nucleus of almost every one of your cells since you were a wee zygote, or fertilized egg cell. They just keep replicating this information again and again and again. This process — the one where your cells (the nuclei of which contain all 46 of those original chromosomes your parents gave you on day one) divide over and over to make new ones when the old ones get tired or damaged — is called mitosis. Mitosis happens when you make new fingernail cells or even when you grow a cancerous tumor. Mitosis is such a workhorse you might not know it has a sister process called meiosis, which is equally important, but not as common. "The key to understanding the difference between mitosis and meiosis is not in the steps, but in the final products of each," says Brandon Jackson, assistant professor in the So, that's easy enough to remember: I...

[ "article:topic", "karyotype", "nondisjunction", "Down Syndrome", "Turner Syndrome", "showtoc:yes", "trisomy 21", "Klinefelter\'s syndrome", "Triple X syndrome", "columns:two", "cssprint:dense", "source[1]-bio-17046", "program:oeri", "licenseversion:30", "license:ck12", "source@https://www.ck12.org/book/ck-12-human-biology/" ] Mitosis or Meiosis? Figure \(\PageIndex\): 4-celled embryo Cell Reproduction You have probably have heard of the importance and prevalence of cell division. While there are a few cells in the body that do not undergo cell division (such as gametes, red blood cells, most neurons, and some muscle cells), most somatic cells divide regularly. A somatic cell is a general term for a body cell, and all human cells, except for the cells that produce eggs and sperm (which are referred to as germ cells), are somatic cells. Somatic cells contain two copies of each of their chromosomes (one copy received from each parent). A homologous pair of chromosomes is the two copies of a single chromosome found in each somatic cell. The human is a diploid organism, having 23 homologous pairs of chromosomes in each of the somatic cells. The condition of having pairs of chromosomes is known as diploidy. Cells in the body replace themselves over the lifetime of a person. For example, the cells lining the gastrointestinal tract must be frequently replaced when constantly “worn off” by the movement of food through the gut. But what triggers a cell to divide, and how does it p...