Cellular Reproduction

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Cellular Reproduction

• Ch. 8

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(8-1) Chromosomes

• DNA protein in a coiled, rod-shaped form that
  occurs during cell division
• Uncoiled form is chromatin
• Histone protein DNA wraps around
• Maintains shape tight packing

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Chromosomes (cont.)

• 2 sister chromatids
• Exact copies of each other
• Connected by centromere
• Cell division separates chromatids
• Each new cell gets 1 copy of each chromosome

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Chromosome

• Each species has characteristic of chromosomes
  in each cell

Ameba 50 Goldfish 94 Alligator 32
Garden Pea 14 Brown bat 44 Grasshopper 24
Bullfrog 26 Horse 64 Carrot 18
Human 46 Cat 32 Lettuce 18
Chicken 78 Onion 16 Chimpanzee 48
Redwood 22 Corn 20 Sand dollar 52
Earthworm 36 Fruit fly 8
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Sex Chromosomes

• Determine sex of organism may carry genes for
  other characteristics
• Humans (X or Y)
• Autosomes all other chromosomes besides sex
• Humans 44 (other 2 are sex)

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Homologous Chromosomes

• Homologues pairs of chromosomes
• Same size, shape, genes
• Different from other homologues
• In sexual reproduction, organism receives 1 copy
  of each autosome from each parent

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Karyotype

• Photomicrograph of chromosome in a living cell
• Humans 22 homologues 2 sex chromo.s

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Diploid

• (2n) cells that contain 2 sets of chromosomes
• Humans 2n is 46
• Haploid (1n) cells that contain 1 chromosome of
  each hom. pair
• Sex chromo.s

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Reproduction

• When sperm (1n) egg (1n) combine to make 1st
  cell of new organism, the new cell is diploid (2n)

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(8-2) Cell Division

• Process in which cells produce offspring cells
• Why do cells divide?
• Size is limited
• Replace damaged cells
• Growth

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Prokaryotic Cell Division

• Binary fission division of prokaryotes into 2
  offspring cells
• 3 stages
• Chromosome copied
• Cell grows
• Cell wall forms cell splits into 2 new
  identical cells

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Eukaryotic Cell Division

• Mitosis (Growth Div.) division of cell producing
  2 identical daughter cells
• 2n ? 2n
• Meiosis (Reduction Div.) division of cell
  producing 4 haploid daughter cells
• 2n ? 1n

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The Cell Cycle

• Interphase
• G1
• S
• G2
• Cell Division
• Mitosis (M phase) nucleus divides
• Cytokinesis cytoplasm divides

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Interphase

• Cells in this stage most
• Time b/w cell divisions
• 3 stages
• G1 offspring grow to mature size
• G0 leave cycle, usually when mature
• S DNA replication
• G2 cell preps for cell division

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DNA Replication

• After replication, each double stranded molecule
  contains 1 old strand 1 new strand of DNA

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Step 1 Prophase

• Chromo.s form from chromatin
• Nuclear membrane disassembles
• Centrioles move to pole
• Spindle fibers form

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Step 2 Metaphase

• Fibers line chromo.s up in the middle of the
  cell
• Metaphase plate

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Step 3 Anaphase

• Sister chromatids separate (become individual
  chromo.s) move to opposite poles

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Step 4 Telophase

• Spindle fibers disappear
• Nuclear membrane reforms
• Chromo.s go back to chromatin
• 2 nuclei per 1 cell

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Cytokinesis

• Division of cytoplasm
• Animals - cell membrane pinches
• Plants - cell plate forms
• Results 2 identical daughter cells

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Cancer

• Uncontrolled growth of cells
• Dont respond normally to bodys control
  mechanisms
• Mutations can interfere w/ ability to slow or
  stop cell cycle

Brain Cancer
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(8-3) Meiosis

• Nuclear division that reduces the of chromo.s
  in new cells to ½ the of the original cell

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2 Stages
2n
Meiosis I
n
n
Meiosis II
n
n
n
n
Results in 4 haploid cells
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Interphase

• Same as mitosis
• 3 stages G1, S, G2
• Prep for meiosis I

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Meiosis I

• 2 haploid cells form from 1 diploid cell
• Reduction Division

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Step 1 Prophase I

• Chromo.s form from chromatin
• Nuclear membrane breaks
• down
• Centrioles move to poles
• Spindle fibers form
• Synapsis occurs

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Definitions

• Synapsis pairing of homologues to form tetrad
• Crossing over chromatids of hom. chromo.s twist
  trade places to exchange DNA (genetic
  recombination)

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Step 2 Metaphase I

• Tetrads line up randomly at the metaphase plate
• Spindle fibers attach

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Step 3 Anaphase I

• Tetrads split each homologue is moved toward
  opposite pole
• Independent assortment random separation of
  maternal paternal chromo.s
• Genetic variety

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Step 4 Telophase I

• Nuclear membrane reforms
• Spindle fibers centrioles disappear
• Each nucleus now has haploid of chromo.s

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Cytokinesis I

• Cytoplasm splits to produce 2 haploid daughter
  cells

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Meiosis II

• No interphase b/w meiosis I II
• 4 haploid cells produced from 2 haploid cells
• Exact same process as mitosis

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Step 1 Prophase II

• Spindle fibers form begin to move towards
  middle of the cell

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Step 2 Metaphase II

• Chromo.s move to midline

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Step 3 Anaphase II

• Chromatids separate move to opposite poles

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Step 4 Telophase II

• Nuclear membrane forms around chromo.s in each
  of 4 new cells

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Cytokinesis II

• End result
• 4 haploid cells

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Gamete Production

• Gamete haploid sex cells
• egg sperm
• Oogenesis egg production
• 1 large egg 3 polar bodies
• Spermatogenesis sperm production
• 4 sperm

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Sexual Reproduction

• Each parent contributes genes offspring is
  different from any other member of their species
  (except id. twin)
• Gives offspring better chance of surviving in a
  changing environment

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Asexual Reproduction

• Offspring is an exact copy of parent
• All cells form through mitosis
• Mainly occurs in prokaryotes
• Bacteria, molds, algae, protozoa

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Asexual Reproduction
Regeneration
Budding
Spores
Binary Fission
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Mitosis vs. Meiosis

• Meiosis
• 2 divisions
• 4 daughter cells
• Each unique
• Diploid to haploid
• Purpose
• Make gametes
• Genetic variation

• Mitosis
• 1 division
• 2 daughter cells
• Exact copies of parent cells
• Diploid to diploid
• Purpose
• Growth
• Repair
• Asexual reproduction

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