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Cell Reproduction
Chapters 9 & 11
Types of Reproduction
Mitosis
Asexual – only 1 parent needed & the
offspring are identical to the parent cell.
Meiosis
Sexual – cells from 2 parents fuse to form
new individual. These cells must have ½
the DNA of the parent cells.
Cell Cycle
G1 – growth phase, most of life span
S – DNA synthesis ( 2-4 hrs)
G2 – short growth period (4-8 hrs)
M – mitosis or meiosis begins
G0 – cells that do not divide
Events of the Cell Cycle
Cell Cycle
Mitosis
Mitosis is division of the nucleus
Cytokinesis is division of the cytoplasm
Nuclear material is DNA
Chromatin – diffuse DNA, spread out
Chromosomes – coiled DNA, compact
Eukaryotes have pairs of chromosomes
figure 09-07.jpg
Figure
9.7
Figure 9.7
Phases of Mitosis
Interphase
Non-dividing stage. G1, S, G2
Cell carries on normal functions.
DNA and centrioles are replicated in
preparation for cell division.
Prophase
Chromosomes coil and become compact.
Chromosomes appear double stranded.
Chromatids attached at the centromere.
Centrioles move to the poles.
Asters form around centrioles.
Spindle fibers extend across the cell.
Nuclear membrane and nucleolus
disappear.
figure 09-09.jpg
Figure
9.9
Figure 9.9
Metaphase
Double stranded chromosomes
individually line up on the equator
Centromeres attach to a spindle fiber
CENTROMERE
CENTRIOLE
CHROMATID
Anaphase
Chromosomes split & separate
and are pulled to opposite poles
of the cell by the spindle fibers
Telophase
Cytoplasm divides (cytokinesis)
New nuclear membranes form
Plant cells build a new cell wall.
Animal cells pinch in and separate.
Terminology
Mitosis
Asexual
Diploid
2n
Zygotes
Meiosis
Type
Chromo.#
Cell types
Sexual
Haploid
n
Gametes
Meiosis
There are 2 cell divisions in meiosis.
Interphase I
Chromosomes & centrioles replicate
Prophase I
Chromosomes coil and become double
stranded.
Centrioles move to the poles.
Asters and spindles form.
Nucleolus and nuclear membrane
disappear.
Homologous chromosomes synapse.
Crossing over occurs. This results in the
creation of variations in the chromosomes
Metaphase I
Chromosomes line up in pairs on the
equator.
Crossing over continues.
Anaphase I
Homologous chromosomes separate and
move to opposite poles.
Each new cell will receive 1 copy of the
original chromosome pairs.
Telophase I
Cytokinesis occurs.
Each cell has half the number of
chromosomes as the original parent cell.
Chromosomes are still double stranded.
Interphase II
Chromosomes are uncoiled, but still
double stranded.
NO DNA replication occurs.
Centrioles are replicated.
Cells contain half the chromosome
number as the parent cell.
Prophase II
Same as Mitosis
Metaphase II
Same as Mitosis
Anaphase II
Same as Mitosis
Telophase II
Same as Mitosis
Results of Meiosis
1 parent cell produces 4 daughter cells
Daughter cells are haploid gametes.
Fertilization results form the fusion of 2
haploid gametes to form a diploid zygote.
Spermatogenesis
Sperm cell formation
4 equal sized gametes form
23
23D
23
46
46D
23
23D
23
Oogenesis
Egg cell formation
1 large egg + 3 polar bodies (die)
23
23
D
46
46D
23
23
23D
23
Mitosis vs. Meiosis
Mitosis
46
Zygote
Diploid
Cells
Fertilization
23
46
23D
23
Meiosis
23D
Haploid
Cells
23
23
Gametes
23
Genetic Variations
Sexual reproduction (fertilization)
Meiosis - independent assortment
Meiosis - crossing over
Random Mutations