Meiosis and mitosis


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Meiosis and mitosis

  1. 1. Meiosis and Mitosis By Syed Arsalan Aijaz Jr.III C
  2. 2. Topic Checklist <ul><li>What is a cell? </li></ul><ul><li>What is a chromosome? </li></ul><ul><li>What does DNA mean? </li></ul><ul><li>What is an Embryo? </li></ul><ul><li>Cell Division </li></ul><ul><li>Types of Cell Division </li></ul><ul><li>Difference between Meiosis and Mitosis </li></ul><ul><li>References </li></ul>
  3. 3. What is a cell? <ul><li>A cell is the most fundamental unit of biological life. All known life, except for viruses, is made up of cells. Cells are also the smallest metabolically functional unit of life, meaning the smallest unit that can take in  nutrients  from the bloodstream, convert them into energy, perform useful functions, and excrete waste. There are two primary types of cells , smaller bacterial cells without a  nucleus , and eukaryotic cells, larger plant and animal cells with a true nucleus. </li></ul>
  4. 5. What is a chromosome? <ul><li>In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure. </li></ul><ul><li>Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division. </li></ul><ul><li>Each chromosome has a constriction point called the centromere, which divides the chromosome into two sections, or “arms.” The short arm of the chromosome is labeled the “p arm.” The long arm of the chromosome is labeled the “q arm.” The location of the centromere on each chromosome gives the chromosome its characteristic shape, and can be used to help describe the location of specific genes. </li></ul>
  5. 7. What does DNA mean? <ul><li>DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria (where it is called mitochondrial DNA  or mtDNA). </li></ul>
  6. 9. What is an Embryo? <ul><li>An embryo is an organism in the early stages of development which cannot survive on its own. The study of embryos is known as  embryology , and it makes up part of a larger branch of science which is interested in reproduction and development. </li></ul>
  7. 11. What is cell division? <ul><li>Cell division is the process that cells go through in order to divide. Cells may divide for several reasons, and there are two types of cell division depending on the purpose. The cell division associated with sexual reproduction is one type, called  meiosis . The other type, the cell division associated with growth and cell replacement or repair, is called  mitosis . In both types of cell division, the nucleus  splits and  DNA  is replicated. </li></ul>
  8. 12. Types of Cell Division <ul><li>There are two types of cell division: </li></ul><ul><ul><li>Meiosis or sexual reproduction </li></ul></ul><ul><ul><li>Mitosis or asexual reproduction </li></ul></ul>
  9. 13. Difference between Meiosis and Mitosis <ul><li>The cell division called  mitosis  produces daughter cells that have all the genetic material of the parent cell — a complete set of chromosomes . However, chromosomes are not the only material that needs to be divided and transferred to the daughter cells: there are  cytoplasm  and the  cell membrane  to divide as well. Cytokinesis  is the process of dividing the cytoplasm and the cell membrane, and this process may follow immediately after mitosis or occur separately, depending on the organism involved. Together, these two processes make up the mitotic phases of the  cell cycle . </li></ul>
  10. 15. <ul><li>Meiosis, on the other hand, reduces the number of chromosomes by half, so that, for example, human egg and sperm cells, called gametes, each have 23 chromosomes and can join to produce a  zygote  with 46. It has two division phases, whereas mitosis has only one. Meiosis in animals is called  gametogenesis. In the unfused state, the egg and sperm are called  haploid  cells — having only a single set of chromosomes, and they become  diploid  — having a pair of each type of chromosome — again when they unite during fertilization. </li></ul><ul><li>Meiosis specifically works to combine the genetic material of two individuals. When there is only one parent in the reproductive cycle — for example, in ferns, which reproduce through spore — the daughter cell must have the full genetic material — all the chromosomes — of the parent cell. Therefore, in the case of the creation of spore —  sporogenesis  — reproduction is accomplished without meiosis. </li></ul>
  11. 17. References <ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul><ul><li> </li></ul>