CELL REPRODUCTION
• Review of Biomolecules
• DNA
• Cell Reproduction
Mitosis (Asexual Reproduction)
Meiosis (Sexual Reproduction)
Biomolecules ??
• Proteins
• Amino Acids (20)
• Nucleic Acids
• Nucleotides
• DNA/RNA
• Carbohydrates
• Monosaccharides
• Sugars
• Lipids
• Fatty Acids
Cell Reproduction
In This Unit:
Introduction to chromosomes
(the cells’ library of genetic material)
2. Study Mitosis and cell division of
Body (Somatic) cells
3. Examine how sex cells (Gametes)
form through a process called
meiosis
1.
P/S:
Reasons for Cell Reproduction
1. Replace/Maintenance (skin, blood, digestive)
2. Growth
3. Repair (scrape knee, break bone)
4. Reproduction of species: pass down genetic
material for continuation of the species
(mutations/adaptions/natural selection)
Structure of DNA
• Stores Genetic Information
• A Double helix ladder of connected nucleotides forming a
sugar-phosphate “backbone” and nitrogen base “steps”
• Each nucleotide of DNA consists of:
A sugar “deoxyribose”
A phosphate
A nitrogenous base:
Adenine
Thymine
Cytosine
Guanine
DNA STRUCTURE
Clip on DNA…compacts tightly
• Visualizing Cell Processes
• DNA structure
• Chromosome Condensation
DNA coiling 1.42 replication, transcription and translation 7.46
*Handout
Chromosomes are counted on karyotypes
Karyotype
Of a Human Somatic Cell:
• 46 chromosomes
• 23 pairs
• 44 autosomes
• 22 pairs
• 2 sex chromosomes
• 1 pair
• XX = female
• XY = male
Allele: Different forms of a
gene (Blue, brown eyes)
?
Down Syndrome
Trisomy 21; Nondisjunction at 21
• Chromatin
Partially “unraveled”
Chromosomes
• Chromosome
A ‘single’ structure …
DNA*nucleosome proteins
• Chromatid
2 identical copies of a
chromosome (attached)
All refer to
the cells’
DNA
content at
different
stages
Chromatin vs Condensed DNA /Chromosomes
95% of the time
Easily Visible,
5% of the time
Homologous Chromosomes
ALLELE FOR EYE COLOR
eye color
locus
(ex-blue)
eye color
locus
(ex-brown)
CENTROMERE
hair color
locus
hair color
locus
From Dad
From Mom
Unreplicated Chromosome, when copied = 2 chromatids
Held together by a centromere- form a replicated chromosome
Homologous chromosomes: 23 PAIRS (From mother/father
…similar in size/shape and centromere position
_____ _____
Sister
Chromatids
(identical)
*Nonsister
TWO TYPES OF CELLS:
SOMATIC and GAMETES

SOMATIC: (Body Cells)
(Body cells: skin/muscle/liver/bone/brain/blood)
Diploid Cells (2n): The # of chromosomes in a
somatic cell 2n = 46? in humans…varies/species

GAMETES: (Sex Cells)
(Sex cells = Gametes = Humans?)

23 Sperm + 23 Egg = 46 Zygote (The fertilized egg)
Plants?
Haploid Cells (n): The # of chromosomes in a
sex cell n = 23 in humans (half a complete set)
2n…n…difference?
• Not the NUMBER of
chromosomes but the
SIZE, COMPLEXITY,
and amount of DNA
The Making of New Prokaryotes:
Binary Fission (asexual)
• DNA attached to the
inner membrane
• DNA (plasmid) copies
• New cell wall forms
• Then splits in two,
creating two bacteria
with IDENTICAL
DNA. replicates in ~20minutes
Bacteria in time lapse .56
(see notepage)
Mitosis + Cytokinesis
Eukaryotic
Cell Cycle:
Repeating
set of
events that
make up
the life of a
cell
Interphase +
PMAT (Mitosis)
+ Cytokinesis
95% Interphase: Growth ,Synthesis of DNA, Preparation for mitosis
Cell Cycle: An Interactive Animation
Cell Cycle Checkpoints- The Controls
Depending on
the presence
Cyclins and cyclin
and action of
dependent
kinases
these (CDK’s)
proteins,
control the cell
the cell cycle
cycle.
can regulate
be speedy
They
gene
expression
or slow,
and it
to allow for cell
may even halt
replication and
altogether.
division.
*PDGF- Platelet Derived
Growth Factor- Wound healing
CELL CYCLE CONTROL
3A3 Cyclins and cyclin-dependent kinases control the cell cycle
3.A.2a The cell cycle is a complex set of stages that is highly
regulated with checkpoints, which determine the ultimate fate of the
cell. Internal controls or checkpoints, internal and external signals
provide stop & go signs at the checkpoints
• Mitosis “Maturation” Promoting Factor (MPF)
• Platelet-derived Growth Factor (PDGF)
• Cancer Disruption in cell cycle control
Cells Alive!
Cell Cycle Control and Checkpoint Activity 6.12
Control of the cell cycle
P53 pp, .43 clip
• “Normal Control”
• ONCOGENES:
Normally stimulate cell
growth
GROW/DIVIDE when
needed (Repair, growth)
STOP for internal or
external controls.
• Growth Factors
• Density dependent
• Anchorage dependent
• SUPPRESSOR
GENES
Normally inhibit cell
growth
• REPAIR GENES
Normally limit
mutations
• Genes are Transcribed
• Mutations
• Methylation (Hyper or
Demethylation)
• Transcription factors
• miRNA
p53 protein:
Transcription Factor
for checkpoint control
genes “the guardian of
the genome”,
regulates the cellular
response to stress and
cancer
PROPHASE
• Chromosomes Condense
• The nuclear envelope disappears
(dotted line = breakdown or forming
• The centrioles move to opposite poled
• The spindle starts to form, growing
out of the centrioles towards the
chromosomes
Metaphase
• Chromosomes line
up on the equator of the cell
• Spindle fibers are attached
to the centromeres
Human Cell- how many
Will be lined across?
Anaphase
• Centromeres divide
• Spindle fibers contract
and the chromosomes are
pulled to opposite poles
Telephase
• In telophase the cell actually divides
• The chromosomes are at the poles of the spindle
• The spindle disintegrates
• The nuclear envelope reforms around the two sets of
chromosomes
• Set for cytokinesis to occur
Cytokinesis
• Division of cytoplasm and its contents
• Results in 2 daughter cells
• Animal cells- Furrow formed
by microfilaments- pinches
plasma in half “cleavage furrow”
• Plant cells- a new cell wall
made of cellulose forms
between the 2 new nuclei
Summary of Mitosis
Plant Cell Cytokinesis
Lab:
DVD: Visualizing Cell Process, DNA, Stages of Mitosis
• Onion Root Tip……Interphase and PMAT
Metaphase
Telephase
with cell
plate
Interphase
Anaphase
Prophase
 DVD: Visualizing Cell Process- DNA- Stages of Mitosis ~30sec
MITOSIS
• Mitosis + Cytokinesis = 2 new cells with the same genetic
information as the original cell
http://www.pbs.org/wgbh/nova/miracle/divi_flash.html
ANIMATION: COMPARISON MITOSIS TO MEIOSIS
Mitosis (body cell) vs. Meiosis (sex cell)
23..STILL
Replicated
Crossing Over
Independent Assortment
Meiosis- Key Differences from Mitosis
Mitosis Creates Body Cells; Meiosis creates Sex cells
1. Meiosis I (PMAT I) involves:
Prophase: homologous chromosomes pair up – called a
‘tetrad’. = Where Crossing Over of non-sister chromatids takes
place. *First source of Genetic Variation- no longer identical.
Metaphase I: Homologous pairs line up on the equatordouble file- Mom with sister chromosome, dad with sister
chromosome. (Double 23 across, not 46)
*Independent Assortment- second source of genetic variation
Anaphase I: Tetrad Splits- Sister chromatids do NOT
separate at the centromere. (Pair of homologous chromatids
split up)
* Do NOT
COPY DNA
again
MEIOSIS II: Separating Sister Chromatids
Meiosis- Key Differences from Mitosis
1. Meiosis reduces the # of chromosomes by half
2. Daughter cells differ from parent and each other
Mitosis- Daughter Cells are Identical (Somatic)
Meiosis- At end 4 different cells….Genetic Variation
3. Meiosis involves TWO divisions; Mitosis only one.
Crossing Over
• Prophase I
• First Source of
Genetic Variation
• Chiasmata- sites of
crossing over, occur in
synapsis- exchange of
genetic material
between non-sister
chromatids
• No longer Genetically
Identical
Independent Assortment: Metaphase I
2nd Source of Genetic Variation
At least (223)
8 million
possible
combinations
from EACH
parent….
64 TRILLION
combinations
for a diploid
zygote
Producing
truly unique
offspring
Spermatogenesi
s vs Oogenesis
Third Source
of Genetic
Variation:
Random
Fertilization
(which sperm
will fertilize
the egg?)