Lecture 4 Outline (Ch. 12

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Lecture 4 Outline (Ch. 12 13)

• Cell Cycle
• II. Cell Spindle Mitosis
• Stages
• Plants vs. Animals
• III. Cell cycle controls
• IV. Genetics Overview
• V. Cell Reproduction
• VI. Karyotypes Meiosis
• Stages
• Compare to mitosis
• VII. Independent Assortment
• VIII. Crossing-over/recombination
• IX. Lecture Concepts

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Cell cycle overview
-repeated
-regenerative
-inputs, outputs
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Cell cycle phases
cell cycle phases
G1 first gap
S DNA synthesis
G2 second gap
Interphase G1, S, G2
M mitotic phase
human cell cycle 24 hrs.
mitosis cytokinesis
M lt 1hr, S 10-12 hrs.
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Cell Cycle
Purpose of cell division?
two identical daughter cells
Divide DNA
- karyokinesis
Divide cell
- cytokinesis
Division to duplicate body cells mitosis
somatic cells

• development
• replacement

Division to form sex cells meiosis gametes
(sperm and egg)
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DNA Terminology
All organisms genes genome
Human genome 30,000 genes 3.2 billion
nucleotides
chromosomes packaged DNA
humans 46 chromo, in 23 pairs
diploid (2n)
most chromosomes two arms with centromere
in middle
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DNA duplication
DNA duplication
each chromosome copied
- sister chromatids
- attached at centromere
condense hugely
chromosomes divided equally to daughter cells
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Mitosis
How are chromosomes separated accurately?
mitotic spindle
- microtubules (MT) assoc. proteins
two poles of spindle
- MT organized
- centrosome centriole pair
MT radiate from centrosomes
- astral MT
- spindle MT
- kinetochore MT
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Stages of Mitosis
Before mitosis
DNA duplicates
centrosomes duplicate
nucleus intact
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Stages of Mitosis
Prophase
DNA condenses
nucleoli gone
spindle forming
Prophase
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Stages of Mitosis
Prometaphase
nuclear membrane breaks
spindle attaches
DNA condensation
Prophase
Prometaphase
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Stages of Mitosis
Metaphase
centrosomes to ends
kinetochores attach
chromosomes line up
at metaphase plate
Prometaphase
Metaphase
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Stages of Mitosis
Anaphase
sister chromatids separate
kinetochore MT shorten
spindle MT lengthen
Metaphase
Anaphase
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Stages of Mitosis
Telophase
nuclear membrane reforms
chromosomes decondense
Anaphase
Telophase
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Stages of mitosis
Cytokinesis
begins during telophase
completed after karyokinesis
- cell membrane pinches in
- cleavage furrow
- actin fibers at midline
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Self-Check
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Arrange mitosis stages in order
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4
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Mitosis in plant cells
karyokinesis same in plant cells
no centrioles, do have centrosomes
cytokinesis different
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Mitosis in plant cells
cytokinesis different in plants
no cleavage furrow
vesicles move on MT
collect at midline cell plate
cell plate becomes cell wall
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Mitosis in plant cells
in dividing plant tissue can find all stages
of mitosis
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Cell cycle controls
transitions between phases?
signals
induce/promote cycle progression
molecular control system
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Cell cycle controls
cycle proceeds until checkpoint
- critical stop vs. go choice
three major checkpoints G1, G2, M
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Cell cycle checkpoints
G1 checkpoint critical
G1 go ahead cell completes S, G2, M
G1 no go cell exits cycle
- non-dividing phase - G0
cells can return from G0 and reenter cycle
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Cell cycle checkpoints
checkpoints signals
1. cyclin-dependent kinase (Cdk)
2. cyclin
Cdk - persists, inactive w/out cyclin
cyclin degraded, accumulates
Cdk cyclin MPF
MPF pass checkpoint
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Cell cycle checkpoints
G1 checkpoint many Cdks cyclins
G2 checkpoint regulated by MPF
M checkpoint make sure all chromosomes
attached before division
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Self-Check
stage prophase
events Chromo condense
Clues Nuc intact Chromo copied
Fill in the chart above below each diagram with
the stage of the cell cycle and what is happening
(events)
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Self-Check

1. Draw and label the cell cycle in order include
   first checkpoint
2. Draw a cell in G1 with 4 chromosomes Draw a cell
   in metaphase with 4 chromosomes
3. Start with G1 cell 6 chromo draw mitosis
   products

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Genetics overview
heredity
- all genes from parents
variation
- your gene combination
genetics
- study of heredity and heritable variation
gene unit of heredity
locus location along chromosome
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Cellular reproduction
asexual reproduction mitotic division
clone
little variation
sexual reproduction two parents
gametes
unique combinations of gene variations
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Cellular reproduction
gametes haploid (1n) one chromosome set
somatic cells diploid (2n) two sets two
parents
karyotype view of 2n set
homologous chromosomes one from each parent
autosomes vs. sex chromosomes
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Karyotypes
Chromosomes from human female cell
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Karyotypes
Aligned by homologues
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Meiosis - introduction
maternal paternal
cell preparing to undergo division
sister chromatids
centromere
non-sister chromatids
homologous chromosomes
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Meiosis overall goal
two parts meiosis I II
meiosis I separate homologues
meiosis II separate sister chromatids
input one 2n cell output four 1n cells
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Meiosis I
interphase
prophase I
metaphase I
anaphase I
-metaphase plate -tetrads -homologues attached to
MT
-homologues separated
-chromo replicate -centrosomes replicate
-condense -synapsis -crossing over
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Meiosis I to Meiosis II
telophase I cytokinesis
prophase II
-no DNA replication prior -cells not identical
-sister chromatids attached -cell is haploid
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Meiosis II
prophase II
metaphase II
anaphase II
telophase II cytokinesis
-sister chromatids metaphase plate
-MT attach to each chromatid -separate
-four 1N cells, genetically distinct
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Self-Check
When does chromosome duplication occur?
What is separated during meiosis I?
meiosis II?

mitosis?
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Self-Check
How many chromosomes?
single or duplicated?
tetrad
one chromosome chromatid
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Mitosis vs. Meiosis
no synapsis
synapsis
2n
separate sister chromatids
separate homologues
separate sister chromatids
1n
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Independent assortment
maternal paternal
random arrangement of homologues
independent assortment
chance of getting paternal homologue
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humans 23 pairs
of mat./pat. combinations?
223, or 8 million
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Crossing-over
maternal paternal
prophase I - synapsis
chromo align gene by gene
crossing-over swap bits of homologous DNA
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Life cycles
meiosis creates haploid cells
gametes (sperm or eggs)
gametes fuse fertilization
create zygote, diploid
Human diversity
Independent assortment Crossing-over Random
fertilization
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Self-Check
stage Prophase I Metaphase I Anaphase I Telophase I Prophase II Metaphase II Anaphase II Telophase II
events
What to look for?
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Lecture 4 concepts

• - Draw a diagram of the cell cycle what happens
  at each step?
• Recognize, describe, and order division stages
  for mitosis
• Define chromosome, karyokinesis,
  cytokinesis, sister chromatid, centromere,
  spindle, checkpoint, G0
• Know different types of spindle microtubules
• Compare and contrast plant and animal cell
  division
• Describe how cyclin and Cdk control checkpoint G2
• Recognize, describe, and order division stages
  for meiosis
• Define heredity, variation, gene, locus,
  chromosome, gamete, somatic, homologue,
  genetics, synapsis
• Explain what a karyotype is and what it is used
  for
• Compare and contrast asexual and sexual
  reproduction
• Describe three BIG ways sexual reproduction
  provides genetic variation
• Write out a list of new terminology and provide
  descriptions