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Chapter 4: Cell Reproduction

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Title: Chapter 4: Cell Reproduction Author: Natalie Fascianella Last modified by: NYC Department of Education Created Date: 9/29/2008 1:18:46 AM Document presentation ... – PowerPoint PPT presentation

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Title: Chapter 4: Cell Reproduction


1
Chapter 4 Cell Reproduction
2
Aim Why is cell division important?
3
The Cell Cycle
  • Series of events that takes place from one cell
    division to the next
  • Length of time to complete a cell cycle is
    different in all cells
  • Most of the life of any eukaryotic cell is spent
    in interphase-period of growth and development
  • Nerve and muscles cells are always in interphase
    (no longer divide)

4
  • During interphase, hereditary material is copied
    and the cell prepares for cell division
  • Cell division begins after interphase
  • Cells need to copy hereditary material before
    dividing so the new cells have a complete set of
    hereditary material to carry out life functions

5
Aim What is the process of mitosis?
6
Mitosis
  • Process in which the nucleus divides to form two
    identical nuclei
  • New nuclei are identical to original nucleus
  • Interphase
  • nucleus divides and chromosomes duplicate forming
    chromatids-two identical DNA strands

7
4 stages of mitosis
  • Prophase
  • Chromatids fully visible
  • Nucleolus and nuclear membrane disintegrate
  • Centrioles move to opposite ends of cell (not in
    plants)
  • Spindle fibers begin to form
  • Metaphase
  • Chromatids line up across the center of the cell
  • Centromere of each chromatids attaches to spindle
    fibers from each side

8
  • 3. Anaphase
  • Each centromere divides
  • Chromatids separate and move to opposite ends of
    cell and become chromosomes
  • 4. Telophase
  • Spindle fibers disappear
  • Nucleus forms
  • Cytoplasm being divided
  • 2 new cells form
  • Animal Cell-cell membrane pinches in middle
  • Plant Cell- cell plate appears forming a new cell
    wall

9
Results of Mitosis
  • Each new nucleus has the same number and types of
    chromosomes as the original
  • Humans
  • Every cell has 46 chromosomes-23 pairs, except
    sex cells
  • All the trillion of cells have the same
    hereditary material
  • Use DNA to become different types of cells
  • Cell division allows growth and replaces damaged
    or worn out cells

10
Aim What is asexual reproduction?
11
Asexual Reproduction
  • New organism is produced from one organism
  • New organisms hereditary material is identical
    to the parents hereditary material
  • 3 forms of Asexual Reproduction
  • Cellular
  • Used by organisms with eukaryotic cells
  • Ex sweet potato growing in jar of water
    (mitosis)
  • Bacteria reproduce asexually by fission
  • Cant use mitosis because they dont have a
    nucleus

12
  • 2. Budding
  • Bud grows from the body of the parent organism
  • Made possible by mitosis
  • 3. Regeneration
  • Uses cell division (mitosis) to regrow body parts
  • Examples sponges, sea stars

13
Aim What is sexual reproduction?
14
Sexual Reproduction
  • Two sex cells come together
  • Formed from cells in reproductive organs
  • Sperm-male
  • Eggs-female
  • Fertilization-joining of egg and sperm
  • Forms a zygote
  • Following fertilization, cell division begins

15
  • Diploid Cells
  • Cells have pairs of similar chromosomes
  • Human body cells-23 pairs, 46 chromosomes
  • Skin, bones, tissues and organs form from diploid
    cells
  • Haploid Cells
  • Do not have pairs of chromosomes
  • Sex cells
  • Have only 23 chromosomes-one from each of the 23
    pairs

16
Aim Why is meiosis needed for sexual
reproduction?
17
Meiosis
  • Produces hapliod sex cells
  • After 2 haploid sex cells combine-a diploid
    zygote forms
  • Two divisions of the nucleus occur
  • Meiosis 1
  • Meiosis 2
  • Results in four sex cells

18
Meiosis 1
  • Chromosome is duplicated
  • Prophase 1
  • Each duplicated chromosome comes near its similar
    duplicated chromosome
  • Metaphase 1
  • Pairs of duplicated chromosomes line up in center
    of cell

19
  • Anaphase 1
  • Each chromatid pair attaches to one spindle fiber
  • 2 pairs of chromatids move away to opposite ends
    of cell
  • Telophase 1
  • Cytoplasm divides
  • 2 new cells form
  • Each new cell has one duplicated chromosome from
    each similar pair

20
Meiosis 2
  • Chromatids of each cell will be duplicated
  • Prophase 2
  • Duplicated chromosomes and spindle fibers
    reappear
  • Metaphase 2
  • Duplicated chromosomes move to middle of the cell
  • Each centromere attaches to 2 spindle fibers
    instead of 1

21
  • Anaphase 2
  • Chromatids separate and move to opposite ends of
    the cell
  • Chromatids now chromosomes
  • Telophase 2
  • Spindle fibers disappear
  • Nuclear membrane forms around the chromosomes
  • After meiosis 2 cytokenisis occurs-the division
    of the cytoplasm

22
Aim What are the parts of a DNA molecule?
23
DNA
  • Deoxyribonucleic Acid
  • Contains information for an organisms growth and
    function
  • DNA code is copied when the cell divides
  • 1952- Rosalind Franklin discovered it is 2 chains
    of molecules in a spiral form
  • 1953 DNA model created by James Watson Francis
    Crick

24
  • Similar to a twisted ladder
  • Each side of ladder is made up of sugar-phosphate
    molecules
  • Rungs of ladder-made of nitrogen bases
  • 4 kinds of nitrogen bases
  • Adenine (A)
  • Guanine (G)
  • Cytosine (C)
  • Thymine (T)
  • CytosineGuanine
  • AdenineThymine
  • These bases occur as pairs

25
Aim What is the function and structure of RNA?
26
Genes
  • Most of your characteristics depend on the kinds
    of proteins your cells make
  • The instructions for making a specific protein
    are found in your genes
  • Are a section of DNA on a chromosome
  • Determine the order of amino acids in a protein
  • Changing the order makes a different protein
  • Found in the nucleus

27
  • Proteins are made on ribosomes
  • Codes for making proteins are carried from the
    nucleus to the ribosomes by RNA
  • RNA
  • Made in the nucleus on a DNA pattern
  • 4 bases adenine, guanine, cytosine and uracil
    (U)
  • Molecules contain the sugar ribose
  • 3 types of RNA

28
  • mRNA
  • Messenger RNA
  • Protein production begins when it moves into the
    cytoplasm
  • Carries codes to make the amino acids bond
  • rRNA
  • Ribsosomal RNA
  • Ribosomes made of it
  • tRNA
  • Transfer RNA
  • Bring amino acids to the ribosomes
  • Attach with the mRNA to make a protein

29
Aim How do mutations occur?
30
Mutations
  • Happens when DNA is not copied correctly
  • Are any permanent change in the DNA sequence of a
    gene or chromosome of a cell
  • X-rays, sunlight, and some chemicals may cause
    mutations
  • Examples
  • Having an extra chromosome
  • Missing a chromosome

31
  • Without correctly coded proteins an organism can
    not grow, repair or maintain itself
  • Can cause death
  • Mutations in body cells may or may not be life
    threatening
  • Mutations in sex cells cause all the cells that
    are formed to have the mutation
  • Some mutations have no effect
  • Some can be beneficial
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