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Chapter 10: Cell Division and Growth. Chromosomes. When cells are NOT dividing, DNA is found in the nucleus in the form of uncoiled chromatin . What does this look like?. Chromosomes.

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chromosomes
Chromosomes
  • When cells are NOT dividing, DNA is found in the nucleus in the form of uncoiledchromatin.
    • What does this look like?
chromosomes1
Chromosomes
  • When the cell is getting ready to divide, chromosomes form as the DNA wraps and coils tightly around histones.
chromosomes2
Chromosomes
  • Chromosomes: carriers of genetic information that is copied and passed to new cells
    • Genes: section of DNA that controls production of a protein; found on a chromosome
chromosomes3
Chromosomes
  • Structure of Chromosomes
    • Sister Chromatids: two identical halves of the chromosome (made when DNA copies itself)
    • Centromere: middle area where two chromatids are joined
slide6

Non-replicated

Replicated

chromosomes

Centromere

Sister chromatids

ONE chromosome

chromosomes4
Chromosomes
  • Chromosome Numbers
    • Each species have a characteristic number of chromosomes
      • Fruit Flies = 8 chromosomes (4 pairs)
      • Adder’s Tongue Fern = 1, 263 chromosomes (631 pairs)
      • Humans = 46 chromosomes (23 pairs)
chromosomes5
Chromosomes
  • TWO Types of Chromosomes
    • 1. Sex Chromosomes: determine the sex of an organism
      • Humans have 2 of these chromosomes (1 pair)
        • Males: XY
        • Females XX
chromosomes6
Chromosomes
  • TWO Types of Chromosomes
    • 2. Autosomes: remaining body chromosomes
      • Humans have 44 of these chromosomes (22 pairs) that “travel” in pairs
chromosomes7
Chromosomes
  • Homologous chromosomes: two chromosomes in a pair; 1 copy from each parent
    • You have 2 of every chromosome that carry genes for the same trait, but they are NOT identical
        • Ex: Chromosome 19 contains genes for hair color
          • Mom’s #19 could have the “blonde” hair gene
          • Dad’s #19 could have the “brown” hair gene
slide12

A

a

B

b

The letters are the genes

Upper case and lower case letters are versions of the genes

C

c

D

d

E

e

F

f

chromosomes8
Chromosomes
  • Chromosomes in each cell
    • Diploid: a cell containing two copies of each chromosomes (both chromosomes in the homologous pair)
      • Abbreviated: 2N
      • Human Ex: skin cell, muscle cell (any BODY cell) 2N = 46
chromosomes9
Chromosomes
  • Chromosomes in each cell
    • Haploid: a cell containing one copy of each chromosomes
      • Abbreviated: N
      • Human Ex: Sperm & Egg cells (any SEX/gamete cell); N =23
cell size limits
Cell Size Limits
  • Organisms grow by producing more cells
    • Cell size is usually comparable between a young and old animal; the older animal just has MORE of them
cell size limits1
Cell Size Limits
  • Why can’t cells continually grow larger?
    • DNA “Overload”: it can’t meet all the cells needs/demands
cell size limits2
Cell Size Limits
  • Why can’t cells continually grow larger?
    • Exchanging Materials:
      • Rate at which materials are exchanged depends on the cell membrane (surface area of the cell)
      • Rate at which materials are used (oxygen, water) or produced (waste) depends on the volume of the cell
cell size limits3
Cell Size Limits
  • As the length of the cell increases, the volume increases faster than the surface area
    • Hard for cells to keep up with moving materials and wastes in and out so the cell divides
cell division in eukaryotes
Cell Division in Eukaryotes
  • TWO types of cell division
    • 1. Mitosis: Cell division that produced body cells identical to the original parent cell (diploid)
      • Examples of cells that do this: skin, muscle, heart
    • 2. Meiosis: Cell division that produces gametes with half the number of chromosomes as the parent cell (haploid)
      • Ex of cells that do this: sperm and egg; GAMETES ONLY
cell division in eukaryotes1
Cell Division in Eukaryotes
  • Cell Cycle: sequences of growth and division of the cell
    • THREE STEPS OF THE CELL CYCLE
      • 1. Interphase (most time spent here)
      • 2. Mitosis
      • 3. Cytokinesis
cell division in eukaryotes2
Cell Division in Eukaryotes
  • How long does it take for a cell to go through one cell cycle?

It all depends on the cell.

A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph.

cell division in eukaryotes3
Cell Division in Eukaryotes
  • 1. Interphase: time when the cell is NOT dividing
    • THREE PHASES OF INTERPHASE
      • 1. G1 = cell grows, makes organelles
      • 2. S = DNA copied
      • 3. G2 = cell makes centrioles; normal metabolism preparing to divide
cell division in eukaryotes4
Cell Division in Eukaryotes
  • 2. Mitosis: dividing of the cell’s nucleus
    • FOUR PHASES OF MITOSIS
      • 1. Prophase
      • 2. Metaphase
      • 3. Anaphase
      • 4. Telophase
cell division in eukaryotes5
Cell Division in Eukaryotes
  • 1. Prophase: longest phase of mitosis
    • Chromatin coils into visible chromosomes (sister chromatids)
    • Nuclear envelope/membrane starts to disappear
    • Spindle fibers appear from centrioles (animal cells only)
cell division in eukaryotes6
Cell Division in Eukaryotes
  • 2. Metaphase: shortest phase of mitosis
    • Spindles attach and move chromosomes to line up along the equator (middle) of the cell
cell division in eukaryotes7
Cell Division in Eukaryotes
  • 3. Anaphase:
    • Chromosomes are pulled apart at the centromere by spindles and separated into sister chromatids
cell division in eukaryotes8
Cell Division in Eukaryotes
  • 4. Telophase
    • Sister chromatids reach opposite poles (sides of the cell)
    • Spindles disappear
    • Nuclear envelopes/membranes reappears
    • Cell begins to split into 2 new cells
cell division in eukaryotes9
Cell Division in Eukaryotes
  • 3. Cytokinesis: dividing of the cell’s cytoplasm, forming two new cells
    • Animal cells: 2 new cells are separated by the cytoplasm “pinching in”
cell division in eukaryotes10
Cell Division in Eukaryotes
  • 3. Cytokinesis:
    • Plant cells: 2 new cells cell plate separated by a cell plate that helps form the cell walls
cell division in eukaryotes12
Cell Division in Eukaryotes
  • Meiosis: Cell division that produces gametes with half the number of chromosomes as the parent cell (haploid)
  • 2 separate cell divisions: meiosis I and meiosis II
    • Interphase and Cytokinesis occur with both divisions
cell division in eukaryotes13
Cell Division in Eukaryotes
  • Meiosis starts with 1 diploid cell and ends with 4 haploid cells
    • Each gamete has half the number of chromosomes as a diploid cell

1 diploid cell with 4 chromosomes

4 haploid cells with 2 chromosomes each

cell division in eukaryotes14
Cell Division in Eukaryotes
  • MEIOSIS 1
    • Prophase I
      • DNA coils into tetrads(pair of homologous chromosomes)
      • Spindles appear
      • Nuclear envelope/membrane disappears
      • Crossing over occurs: DNA is swapped between chromosomes in a pair
cell division in eukaryotes15
Cell Division in Eukaryotes
  • MEIOSIS 1
    • Metaphase I
      • Tetrads are moved by the spindles and line up along the equator
cell division in eukaryotes16
Cell Division in Eukaryotes
  • MEIOSIS 1
    • Anaphase I
      • Tetrads pulled apart by the spindles and separated into chromosome
      • Chromosomes begin movingto opposite ends of the cell
cell division in eukaryotes17
Cell Division in Eukaryotes
  • MEIOSIS 1
    • Telophase I
      • Chromosomes reach opposite sides of the cell
      • Spindle disappears
      • Nuclear envelope/membrane reappears
      • Cytokinesis occurs after this step, forming 2 new cells, which then go through interphase again
cell division in eukaryotes18
Cell Division in Eukaryotes
  • Meiosis II--has 4 stages, PMAT II
    • Each stage--occurs just like the stages of mitosis

Prophase II

Metaphase II

Anaphase II

Telophase II

cell division in eukaryotes19
Cell Division in Eukaryotes
  • MEIOSIS II
    • Prophase II
      • Spindle appear in each of the 2 new cells
      • Nuclear envelopes/membranes disappears
cell division in eukaryotes20
Cell Division in Eukaryotes
  • MEIOSIS II
    • Metaphase II
      • Sister chromatids line up in the middle/equatorof the cell.
cell division in eukaryotes21
Cell Division in Eukaryotes
  • MEIOSIS II
    • Anaphase II
      • Spindles split centromeres and sister chromatids separate
      • Chromatids start to move to opposite ends of the cell
cell division in eukaryotes22
Cell Division in Eukaryotes
  • MEIOSIS II
    • Telophase II
      • Sister chromatids (haploid) reach opposite ends of the cell
      • Spindles disappear
      • Nuclear envelopes/membranes appear
      • Cytokinesis follows this step forming 4 new cells
cell division in eukaryotes23
Cell Division in Eukaryotes
  • Sooooo, what happens after meiosis?
    • Sexual reproduction: production and combination of gametes
      • Fertilization: fusion of male and female gametes to form zygote
        • Zygote: diploid cell (2 of each chromosome)

http://video.sciencemag.org/VideoLab/2127025888001/1/medicine