Cell Reproduction

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Cell Reproduction

• Chapter 8

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Chromosomes

• Section 8.1

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Definitions

• Chromosome rod shaped structure made up of DNA
  and proteins
• Sister Chromatids identical halves of a
  chromosomes

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Definitions

• Centromere protein that holds sister chromatids
  together
• Homologous Chromosomes chromosomes that code for
  the same traits that come from your mother and
  your father

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Definitions

• Chromatin less tightly coiled strands of DNA
• Uncoiled so that the cell can read the DNA to
  direct the cells activities
• Chromosomes only occur during cell division
• Chromatin coils up to make chromosomes

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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

• All normal members of the same species have the
  same number of chromosomes in their body cells.

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Sex Chromosomes

• Definition chromosomes that determine the sex of
  the organism
• May carry other genes as well
• Humans X and Y
• Males XY
• Females XX

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Autosomes

• Definition All other chromosomes in the body
  besides the sex chromosomes
• Humans 46 total chromosomes
• 2 sex chromosomes
• 44 autosomes

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Karyotype map of a organisms chromosomes
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Diploid and Haploid Cells

• Cells having 2 sets of chromosomes are diploid
  (2N)
• The haploid number of a human egg or sperm cell
  is 23, and there are no homologous chromosomes in
  either cell (1N)

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Mitosis

• Section 8.2

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Why Cells Divide

• Cell size is limited
• Cells cannot keep growing indefinitely
• Replacement of damaged cells
• Growth - embryo
• Asexual reproduction
• Single celled life forms
• Binary fission
• Sexual reproduction - meiosis

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Eukaryotic Cell Division

• Mitosis (Growth Division) Division of cell
  producing two identical daughter cells
• 2n ? 2n
• Meiosis (Reduction Division) Division of cell
  producing four haploid daughter cells
• 2n ? 1n

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The Cell Cycle (Life Cycle of the Cell)
2 Major Parts 1. Interphase G1 S G2 2.
Cell Division Mitosis nucleus Cytokinesi
s cytoplasm
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Part 1 Interphase

• Stage your cells are in the most amount of time
• When cell does its normal jobs
• Contains 3 stages G1, S, and G2

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G1 Phase
S Phase
G2 Phase
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S Phase DNA Replication

• Process by which DNA builds an exact copy of
  itself
• After replication has occurred, each double
  stranded molecule contains one old strand and one
  new strand of DNA

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• 1879 Walter Flemming used red dye to observe cell
  structures during mitosis, it killed the cells
  and so he had to take pictures at each stage in
  order to come up with a pictorial model of
  mitosis.

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Part 2 The Stages of Mitosis (page 150)
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Mitosis Step 1 Prophase

• Chromosomes (2 chromatids) form from chromatin
• Nuclear membrane disassembles
• Centrioles move to poles
• Spindle fibers form

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Mitosis Step 2 Metaphase

• Chromosomes line up at the middle of the cell
• Metaphase Plate

- Stage where karyotypes are made from!
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Mitosis Step 3 Anaphase

• Sister chromatids (from the same chromosome)
  separate and move to opposite poles

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Mitosis Step 4 Telophase

• Spindle fibers disappear
• Nuclear membrane forms again
• Chromosomes go back into chromatin form
• 2 nuclei (diploid) per one cell

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Cytokinesis

• Division of cytoplasm
• Cell membrane pinches in to form two separate
  cells
• Results 2 IDENTICAL daughter cells

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Animation

• Mitosis

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Mitosis Flip Book

• To receive full credit you must
• 1. Illustrate what is going on in the life cycle
• a) Title Page
• b) Interphase G1, S, G2
• b) Mitosis prophase, metaphase, anaphase,
  telophase
• c) Cytokinesis early late
• d) Finished product
• 2. Diploid (2N) 8
• (represent homologous pairs with 4 different
  colors)
• Need help? Consult your book or your notes!

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Asexual Reproduction

• offspring is an exact copy of parents - occurs in
  lower plants and animals
• (bacteria, molds, algae and protozoa)
• all cells form through mitosis

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Asexual Reproduction
Regeneration
Budding
Spores
Binary Fission
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Mitosis Slides
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Meiosis

• Section 8.3

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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

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Meiosis I

• Formation of 2 haploid cells from 1 diploid cell
• Production of gametes
• Reduction division

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Step 1 Prophase I

• Nuclear membrane breaks down
• Centrioles move to the poles, spindle fibers form
• Synapsis occurs, forming tetrads, allowing for
  crossing over (genetic variety)

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Definitions

• Synapsis When a pair of homologous chromosomes
  partner up inside a dividing cell
• Tetrads the name given to a partner of
  homologous chromosomes during synapsis
• Crossing over chromatids of homologous
  chromosomes twist around and trade places causing
  an exchange of DNA

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Step 2 Metaphase I

• Tetrads line up randomly at the metaphase plate

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Step 3 Anaphase I

• Tetrads are split and each homologue is moved
  toward opposite poles
• Independent assortment the random separation of
  maternal and paternal chromosomes
• Resulting in genetic variety of offspring

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Step 4 Telophase I

• Nuclear membrane reforms
• Spindle fibers and centrioles disappear
• 2 nuclei per cell
• Each nucleus now has HAPLOID number of
  chromosomes
• 2n ? 1n

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Cytokinesis I

• Splitting of the cytoplasm to produce 2 haploid
  daughter cells

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Meiosis II

• NO interphase between meiosis I and II
• The production of 4 haploid cells from 2 haploid
  cells.
• EXACT same process as mitosis!

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Step 1 Prophase II
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Step 2 Metaphase II
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Step 3 Anaphase II
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Step 4 Telophase II
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Cytokinesis II

• End result 4 haploid cells

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Purpose Gamete Production

• Gamete sex cells (egg sperm)
• Oogenesis egg production
• Spermatogenesis sperm production
• Sexual Reproduction genetic diversity of
  offspring

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Page 155
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Sexual Reproduction

• Each parent contributes genes to the offspring.
• each offspring has a different set of inherited
  traits from the parents
• gives offspring a better chance of surviving in a
  changing environment

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Mitosis vs Meiosis

• Meiosis
• 2 divisions
• 4 daughter cells
• Each unique
• Diploid to haploid
• Purpose
• Make gametes/ sex cells
• Leads to 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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Cancer

• Cell cycle control system
• Enzymes in cell control when and where cells
  divide
• Malfunction in system means cells divide at
  inappropriate times and places
• Benign tumor - abnormal mass of essentially
  normal cells
• Stay at original site, dont move
• Cancer uncontrolled cell division

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Cancer

• Problem not only uncontrolled division
• Metastisis
• Cancer cells can move to other sites
• New tumor at that site
• Three treatments
• Surgery to remove tumor
• Radiation
• Chemotherapy
• Last two aimed at controlling division

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Cancer treatments

• Radiation
• Disrupts cell division
• Most actively dividing cells are tumor
• Can damage normal cells- ovaries / testes
• Chemotherapy
• Some disrupt cell division
• Taxol freezes spindle
• Vinblastine prevents spindle formation
• Cancer cells immortal in cell culture
• Normal cells stop growing after 50 culture