The Cellular Basis of Reproduction and Inheritance

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Chapter 8 The Cellular Basis of Reproduction and
Inheritance
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The Birds and the Bees
Asexual vs. Sexual reproduction
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LE 8-3aa
Plasma membrane
Prokaryotic chromosome
Cell wall
Duplication of chromosome and separation of
copies
Continued elongation of the cell and movement of
copies
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LE 8-3ab
Continued elongation of the cell and movement of
copies
Division into two daughter cells
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LE 8-3b
Prokaryotic chromosomes
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Colorized TEM 32,500
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Figure 8.4A
Chromosomes
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LE 8-4
Sister chromatids
Chromosome duplication
Sister chromatids
Centromere
Chromosome distribution to daughter cells
TEM 36,600?
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LE 8-5
The Cell Cycle
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Mitosis

• Division of the nucleus
• Results in two nuclei that have the same
  chromosome number as the parent
• The two nuclei are genetically identical

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Mitosis

• Divided into 5 phases
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase
• Phases are determined by chromosome movement
• Chromosome movement determined by mitotic spindle
• Mitotic spindle controlled by centrosome

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Mitosis
INTERPHASE
PROPHASE
PROMETAPHASE
Fragments of nuclear envelope
Early mitotic spindle
Centrosome
Centrosomes (with centriole pairs)
Kinetochore
Chromatin
Nucleolus
Nuclear envelope
Plasma membrane
Chromosome, consisting of two sister chromatids
Centromere
Spindle microtubules
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LE 8-6ba
Mitosis (cont.)
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Cleavage furrow
Nucleolus forming
Metaphase plate
Nuclear envelope forming
Daughter chromosomes
Spindle
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LE 8-6ab
Mitosis (cont.)
INTERPHASE
PROPHASE
PROMETAPHASE
LM 250?
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LE 8-6bb
Mitosis (cont.)
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
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Cytokenesis (animal cell)
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Cytokenesis (animal cell)
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Cytokenesis (plant cell)
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Cytokenesis (plant cell)
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Growth Factors

• Proteins required for cell division
• Most cells will not divide without them
• Serve as controls for the cell cycle
• Checkpoints

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Cancer

• Kills 1 out of 5 Americans
• Disease of the cell cycle
• Cells dont respond to the normal cell cycle
  checkpoints
• Cancer cells divide out of control and can invade
  other parts of the body

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Cancer
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Types of Cancer

• Carcinomas originate in external or internal
  body coverings (e.g. skin or intestinal lining)
• Sarcomas originate in support tissue (e.g. bone
  or muscle)
• Leukemias bone marrow
• Lymphoma spleen and lymph nodes

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Chromosome arrangement

• Somatic cells typical body cells
• 46 chromosomes in 23 pairs (humans)
• Each pair is called homologous chromosomes
• Gametes sex cells
• 23 chromosomes

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Homologous chromosomes

• 22 of the pairs (autosomes) are true homologues
• One of each came from mom and dad
• Identical in length and type of genes carried
• Genes on each are slightly different
• Sex chromosomes (23rd pair) dont match up
  exactly (X vs Y)

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Meiosis

• Produces haploid cells
• Results in four daughter cells
• All are haploid
• All are genetically unique from each other and
  from the parent
• DNA replicated before meiosis begins
• Two stages
• Meiosis I separates homologous chromosomes
• Meiosis II separates sister chromatids

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Sexual Reproduction leads to genetic variation

• 3 process that contribute to variation
• Crossing over during prophase I
• Orientation of homologues during metaphase I
• Random fertilization

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Tetrads ? 4 gametes
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Crossing Over
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Karyotype
Centromere
Sister
chromatids
Pair of homologous
chromosomes
2,600?
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Alterations in Chromosome Number

• Nondisjunction when a pair of chromosomes fail
  to separate
• Meiosis I when homologs fail to separate
• Meiosis II when sister chromatids fail to
  separate
• Can happen in autosomes or sex chromosomes

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Alterations in Chromosome Number
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Alterations in Chromosome Number Autosomes
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Down Syndrome

• Nondisjunction in chromosome 21
• AKA trisomy 21
• Results in 47 chromosomes (instead of 46)
• Affects 1 in 700 births
• Incidence increases dramatically with age of
  mother

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Alterations in Chromosome Number Sex Chromosomes
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