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Animal Body
Arthropods
Biochem
Cell Cycle
Cell Interactions
Cell Structure
Circulation
Respiration
Communities
Digestion
DNA
Ecosystems
Energy
Evolution Evidence
Future of
Biosphere
Genetic Engineering
Gene Function
Genetics
Hormones
Human Evolution
Immunity
Species
Interaction
Kidneys
Locomotion
Membranes
Mollusks
Mutation
Nervous
Non-Coelmic
Photosynthesis
Plant Physiology
Population Genetics
Population
Dynamics
Cellular Respiration
Sensory
Speciation
Taxonomy
Vertebrates
Vertebrate
Org
Vocabulary:
1,2,3,4,5,6,7,8,9,10,
11,12,13,14,15,
16,17,18,19,20,
21,22,23,24,25,
26,27,28,29,30,
31,32,33,34,35,
36,37,38,39,40,
41,42,43,44,45,
46,47,48,49,50,
51,52,53,54
Cell Cycle
1. Mitosis -ef: Replication of genetic materials in order to
produce identical cells
2. Prokaryotic Cell Division
Bacteria
Circular DNA
Single strand DNA
Attached at particular site on the cell membranes
Replication Origin
Where DNA replication begins
Enzymes mediated process
Results in exact copy of the chromosome attached
side by side to the original
Cell Division
Size dependent (Surface area to volume ratio)
Called “Binary Fission”
New cell wall and membrane begin to form between
the two copies of DNA
Equal distribution of cellular material (Form of
Asexual Reproduction)
Identical copies of parent are produced
3. Eukaryotic Cell Division
It is a linear molecule
Coils up into chromosome
Fleming - 1882 (Viewed “Mitosis”)
Humans have 46 chromosomes
Ducks - 80
Possum/Toad - 22
Fruit Fly - 8
Penicillin - 1
Double Helix
½ billion nucleotides per chromosome!!
2 inches long ~> 1000 books w/ 1000 pages w/
500 words per page
Chromosomes
Made up of DNA & protein (40% DNA - 60% Protein)
Exists as chromatin (uncoiled)
Coiling
Every 200 nucleotides is a little ball of protein
with DNA wrapped around it
Nucleosomes -
8 histones
W/ DNA bound to it
DNA is a (-) molecule
Histones are (+) proteins (most proteins are -)
Super coiling ~> nucleosomes of DNA segments
coiling tightly together
Chromatin
Heterochoromatin - condensed portions of DNA; inexpressible
Euchromatin - uncondensed portion; expressible
Final coiling occurs during cell division, called
a chromosome
Karyotype - picture (array) of chromosomes
Differences in Chromosomes
Arm Length
Location of centromere
Constricted regions (pinche d)
Counting centromeres to determine the number of
chromosomes
4. Cell Cycle
Cells have varying lengths of cycles
Embryo – 20 min
Fruit Flies – 8 min
Most organisms have @ 24hrs, some however, last years
M phase is about 1 hr
Some cells stay in GO (dormant in reproduction)
Nerve cells; muscle cells (injury can stimulate cell cycle)
|
Growth |
Synthesis |
Mitosis |
Cytokinesis |
|
|
G1 |
S |
G2 |
M |
C |
|
“Gap” “Growth” Primary growth -Chromatin- |
Genome Replication -Chromatin- |
Chromosome condensation Microtubule synthesis Organelle replication |
“Mitosis” Chromosome separation |
“Cytokinesis” Cell Division |
- G1, S, G2
- Cell growth
- DNA replication ~> middle to end of interphase
- Protein synthesis
Mitosis
- Prophase
- Metaphase
- Anaphase
- Telophase
Mitotic Cycle
Interphase (G, S, G2)
Chromosomes replicate during S producing two daughter copies called “sister chromatids”
Sister chromotids bind together to a centromere
Centromere
Highly condensed sequence of DNA
220 nucleotids long
Bound to a protein called “Kinetochore”
Chromosomes condense during G2
Centrioles replicate (coordinated by microtubule s) (not in plants)
Prophase
Chromosomes condense to visibility w/ light microscope
Nucleolus disappears \ NO RNA synthesis
Assemble microtubule apparatus
Centriole pairs separate
Aster Formation
Nuclear membrane disintegrates; contents “stored” in ER
Plane of cell division is ^ to spindle fibers
Metaphase
Sister chromatids align along the center of the cell. “Metaphase Plate” <~ Not a true structure
Centromere begin to divide at kinetochores
Anaphase
Physical separation of sister chromatids
Poles separate by microtubule sliding
Sister chromatids go to opposite poles by microtubular shortening
Telophase
Mitotic apparatus disassembles
Nuclear envelopes established
Normal genetic activities resume
Actin Filaments
- Tightens membranes; pinching ~> “Cleavage Furrow”
Cell Plate
- Cellulose precursor
- “Wall” eventually becomes cell wall
Cytokinesis
- Separation of cells
- Cells return back to normal activities
Cell Cycle Control
General Control
P53 Gene – does checking on DNA
Cell cycle is controlled by various checker proteins at several points
G1 check points ~> assesses cell growth
G2 check points ~> DNA replication
M check point
Occurs at metaphase
Initiates the rest of mitosis
Assesses DNA (pair correctly)
Molecular Control
CdK
Cyclin-dependent protein kinases
Phosphorylate serine & theronine of important molecules
Eukaryotes – different CdK for each check point
Phosphorylation activates that molecules to cause procession of process
MPF
· Mitosis Promoting Factor
· Causes you to move to next check
G2 Check Point
· G2 cyclin is produced during G2. The G2 cyclin binds to CdK to form MPF. MPF phosphorylation is positive feedback. When MPF levels reach a threshold M is triggered. MPF in mitosis causes degragation of of cyclin. Loss of cyclin is loss of MPF. Drop below threshold, mitosis stops.
G1 Check Point
· Same function as G2
· Cell size sends signal to make cyclins & CdK
· High enough ratio triggers production of CdK & cyclins need for S
Cell Cycle On-Off Controls
In eukaryotes, growth factors produced in a variety of situations are what stimulate or inhibit cell division
Molecules which are intracellular signals
50 known – PDGF – “Platelet Derived Growth Factors”
PDGF
Override regular control on cell division
Bind to receptor (specific)
This & EGF (Epiderma l) are general factors
Others are specific
Need a combination of factors to complete task
Deprive cells of these & they stop in G1
Cancer
Uncontrolled cell growth
Proto-oncogenes
· Have the ability to be oncogenes
· Usually cause cell division
· BRCA1 – Breast Cancer
Onocogenes
· Genes which have mutated and are cancerous
· 30+ types
· myc, ras, foc, jun (stimulate cyclin/CdK production)
· Dominant: only one mutated copy will cause cancer
Tumor Suppressor Genes
· Block division by inhibiting cyclin to CdK binding
· Recessive: both copies must mutate to cause cancer
Dephosphorylation
· Rb binds myc/fas etc. Growth factors activate phosphorylating kinases which causes Rb to release proteins & allow division to occur
p53
· “Guardian Angel Gene”
· Makes p53 protein
· DNA checker
· Repairs damage or initiates **Apoptosis**
Meiosis/Sexual Reproduction – “Reduction Division”
Gametes – (haploid)
Egg (oocyte)
Sperm (spermatocyte)
Somatic – (diploid)
Body Cells
Fuse to form a zygote in process of fertilization, or syngamy
To do this, gametes must have a way to produce # of chromosomes in half or else you would get unwieldy amounts of DNA
\ Meiosis – reduction division where # of chromosomes is cut in half during gamete formation
Sexual Life Cycle
Alteration of Generations
Duplication by mitosis
Protists – mitosis/meiosis by individuals
Plants – mitosis ~> meiosis ~> mitosis
Animals – Germ line cells; put aside at beginning
Stages of Meiosis
Two Divisions
Diploid ~> haploid
Haploid ~> haploid
Unique Features
Homologues join along length & exchange genetic material (crossing over)
No replication between divisions
Two Phase – Meiosis I & Meiosis II
Meiosis I
Prophase I
· Chromosomes coil to visibility
· Homologous pairs live up in synapsis to form a tetrad
· A synaptonemal complex forms between the homologues
· DNA unwind & forms pairs with DNA on other homogue (1 w/ 1A)
· DNA segments are exchanged (crossing over)
· 2 copies of two versions of each of 23 gene types
· Chiasmata – places of contact between homologues that serve as evidence for crossing over