How do cells divide - PowerPoint PPT Presentation

1 / 23
About This Presentation
Title:

How do cells divide

Description:

At the end of this unit you should be able to answer the following questions: ... Each chromosome then splits longitudinally, forming two identical chromatids. 10 ... – PowerPoint PPT presentation

Number of Views:16
Avg rating:3.0/5.0
Slides: 24
Provided by: aoibhi
Category:

less

Transcript and Presenter's Notes

Title: How do cells divide


1
How do cells divide?
2
Unit Objectives
  • At the end of this unit you should be able to
    answer the following questions
  • Explain why mitosis is important
  • Detail what happens in the steps of mitosis
  • Compare mitosis in plant and animal cells
  • Compare asexual and sexual reproduction
  • Describe the stages of meiosis and explain why it
    is needed for sexual reproduction

3
Vocabulary
  • Please use your text books to find the meaning of
    the following words
  • Gametes
  • Fertilization
  • Haploid
  • Diploid
  • Asexual reproduction

4
Prokaryotic Cell division
  • Bacteria divide by binary fission

5
Eukaryotic Cell Division
  • The cell cycle is a sequence of events in the
    life of a cell from the end of one cell division
    to the beginning of the next cell division.
  • Cell cycle is composed of 2 parts
  • Interphase
  • growth preparation
  • Cell division

6
Cell Cycle
  • Cell spends 90 of life in interphase
  • Interphase is the part of the cell cycle during
    which normal cell activities take place
  • It is also the time during which cell growth and
    DNA replication happen.

7
Interphase
  • Interphase is divided into 3 phases
  • G1 period of cell growth
  • S genetic material duplicates
  • G2 cell prepares to divide

8
S Phase of Cell Cycle
  • Replication is when the chromosomes make exact
    copies of themselves to form sister chromatids
    joined at the centromere

9
Chromatids
  • During cell division, S- phase, DNA condenses to
    form short, tightly coiled, rod like chromosomes.
    Each chromosome then splits longitudinally,
    forming two identical chromatids.

10
Why do cells divide?
11
Why do cells divide?
  • 1.    Growth - cell division leads to the
    formation of a fully grown individual.
  • 2.    Repair and rejuvenation cells vary in
    their ability to repair tissues ex. liver cells
    only divide when damaged, nerve and muscle cells
    never divide when mature and skin divide
    frequently

12
Why do cells divide?
  • 3.    Reproduction
  •        If the offspring are produced by only one
    parent this is called asexual reproduction. The
    offspring are genetically identical to the parent
    and are the result of mitotic cell division.
  •        Sexual reproduction produces offspring
    from the combination of genetic material from 2
    parents this requires meiosis
  •  

13
Cell division
  • Two types of cell division
  • Mitosis
  • Meiosis

14
Mitosis
15
Mitosis
  • Is the process by which the nucleus divides
    forming 2 identical nuclei each with a complete
    set of chromosomes.

16
Mitosis
  • There are 4 phases in mitosis prophase,
    metaphase, anaphase and telophase.

17
Prophase
  •       Nucleolus disappears and nuclear envelope
    breaks down
  • Chromatin condenses to form chromosomes
    that are visible when viewed under microscope
    each contains a pair of sister chromatids
  • Centrioles move to opposite sides of the nucleus
  • Spindle fibers are formed

18
Metaphase
  • Chromosomes line up at the center of the cell
    (equator) called metaphase plate
  • Shortest phase

19
Anaphase
  • Centromere divides
  • Chromosomes separate and move to opposite sides
    (poles) of cell
  • Cell membrane begins to pinch in (animal cells)

20
Telophase
  • 2 new nuclei are formed
  • Nucleolus reappear
  • Spindle breaks down
  • Chromosomes lengthen and thin out to form
    chromatin.
  • Cell plate forms in plant cells

21
Division of Cytoplasm
  • Begins during telophase
  • Cytoplasm divides
  • In plant cells a cell plate continues to form
    across middle of cell

22
Comparison of mitosis between plant and animal
cells
  • 1.    Animal cells contain centrioles, which
    duplicate as mitosis begins, each pair migrate to
    opposite poles of cell. The spindle forms between
    these centrioles.
  • 2.    In animal cells there is no cell plate
    formation

23
Plant vs. Animal Cell Division
  • 3.    Cell division is evident in anaphase in
    animal cells, but not till telophase in plant
    cells
Write a Comment
User Comments (0)
About PowerShow.com