Chapter 9 How Cells Reproduce

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Chapter 9 How Cells Reproduce

• Start with 3 questions
• What kind of information guides inheritance?
• How is the information copied in a parent cell
  before being passed to the daughter cell?
• What kind of mechanisms actually parcel out info
  to daughter cells?

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9-1 Overview

• Mitosis nuclear division in somatic cells
• Growth, replacing cells, tissue repair
• Plants, animals, fungi, protists
• Meiosis formation of gametes/spores
• Basis of sexual reproduction
• Develop from germ cells
• Prokaryotes?
• Binary fission (p. 336)?

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Chromosomes

• Characteristic number
• Orderly coiling
• DNA winds 2x around histones to make nucleosomes
• Centromere
• Kinetochore

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Nuclear DNA
one chromosome (threadlike and now duplicated
two DNA molecules proteins)?
one chromosome (one dispersed DNA molecule
proteins not duplicated)?
one chromosome (duplicated and also condensed
tightly)?
p.61
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9.2 Cell Cycle

• Series of events from one cell division to the
  next

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Interphase

• G1
• Growth/functional
• S
• Synthesis of DNA
• G2
• Prepare for division

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Mitosis and C-some

• Diploid
• 2n
• 2 of each type

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9.3 Closer look

• Prophase
• C-somes visible
• Centrioles duplicate
• Nuclear envelope
• MT docks at kinetochores

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Metaphase

• Alignment of c-somes between spindle poles

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Anaphase

• Sister chromatids move to opposite spindle poles
  by motor proteins

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Telophase

• C-somes reach poles
• Decondense
• Vesicles reform envelope

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9.4 Cytokinesis

• Plants
• New fibers made before prophase
• Vesicles from Golgi fuse and deposit materials
  for cell plate

• Animals
• Contractile ring
• Cleavage furrow

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Identifying phases of Mitosis
Phase Determination
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9.5 When Control is lost

• Cell cycle checkpoints
• Proteins monitor DNA structure
• Proteins monitor proceeding phases
• Favorable conditions?
• Kinases
• Growth factors

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Architecture of control system

• Growth assessed at G1 checkpoint
• DNA replication success assessed at G2
• Mitosis assessed at M checkpoint

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Molecular Mechanisms

• Cyclin dependent protein kinases (Cdks)?
• Cyclins bind to Cdks, allow them to work as
  enzymes
• G2 - MPF
• Growth factors stimulate
• Usually everyone gets equal amounts
• Specific cell surface receptors
• Broad or specific

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Tumor supressors

• Inhibit
• Prevent binding of cyclins to CdKs
• Recessive
• Gene p53 role in G1 checkpoint, checks for DNA
  errors
• Repair or not

Figure 2 p53 re-enforces G1 and G2 cell cycle
arrest after DNA damage through the
cyclin-dependent kinase inhibitor p21WAF1/CIPI
Mdm2 and Bax are other p53 transcriptional
targets, with Mdm2 regulating p53 levels and Bax
mediating apoptosis
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Proto-oncogenes

• Stimulate
• Mutation oncogene
• Dominant
• Changes in surface receptors

Figure 2. A modified receptor. Under normal
circumstances membrane-bound receptors require
the binding of their ligand to be in an activated
state. In contrast, receptors encoded by
oncogenes do not require the regulatory step of
ligand binding to be active.
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Cancers

• 4 characteristics
• Grow divide abnormally
• Cytoplasm membrane altered
• Weakened capacity for adhesion
• Lethal effects

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Control of the cell cycle game
http//nobelprize.org/educational_games/medicine/2
001/