Post on 14-Jan-2016
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Regents Biology
Cell Cycle – Interphase + Mitosis
Interphase – where the cell spends most of its time G1, S, G2 Doing GRRSNERT
Mitosis – cell division PMAT Making new cells Making new DNA
IPMAT
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Going from egg to baby…. the original fertilized egg has to divide…
and divide…and divide…
and divide…
Getting from there to here…
Fertilized egg = zygoteLevels of organization: cells tissues organs organ
systems
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Why do cells divide… One-celled organisms for reproduction
asexual reproduction (clones) – binary fission Examples: paramecia, amoeba
Multi-celled organisms for growth & development
from fertilized egg to adult for repair & replacement
replace cells that die from normal wear & tear or from injury
Cells MUST remain small to be efficient
amoeba
starfish
Regeneration – part of an organism
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In Dividing cells… What has to be copied
DNA - instructions to make proteins organelles cell membrane - made of lipids and proteins lots of other
molecules Enzymes –
Type of protein
animal cellplant cell
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Forms of DNA Chromatin
Chromosomes
Chromatids 4 single-stranded chromosomes
Unwound DNA
DNA wound or coiled
Replicated DNA – held together by centromeres•2 chromosomes – count centromeres•4 chromatids
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DNA must be duplicated…
nucleus
cell
DNA in chromosomes
nucleus
cell
duplicated chromosomes
• Start with 2n OR diploid chromosomes
• Two of each “kind” – pairs of homologous chromosomes
• Carry similar information
• STILL have 2n or diploid chromosomes – but have chromatid copies
• # chromosomes = # centromeres
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Same size and shape Similar “banding pattern”
In sexual reproduction –
one from each pair comes
from each parent
Homologous Chromosomes - Pairs of chromosomes that carry similar genetic info
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Before Mitosis: Interphase
G1/S/G2: cell copies DNA, makes organelles, GRRSNERT
MOST time spent in this phase doing the cell’s “job”
nucleus
One 2ndiploid cell
DNA (Chromatin)
Copy DNA!
(interphase)
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Mitosis: PROPHASE Prophase: DNA winds into chromosomes
DNA is wound up into chromosomes to keep it organized so they are visible
Nuclear membrane starts to break down
nucleus
one 2n diploid cell
duplicated chromosomes
Wind up!
(prophase)
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Mitosis: METAPHASE Metaphase: chromosomes line up in middle
Along the “equator” attached to protein “spindles” that will help
them move to opposite “poles”
Line up!
(metaphase)
Spindle fibers
Poles – centrioles in animal cells; asters in plant cells
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Mitosis: ANAPHASE Anaphase: Chromatids separate
centromeres duplicate, homologous chromatids split, separating chromatids
start moving to opposite ends or poles
Separate!
(anaphase)
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Mitosis: TELOPHASE (including cytokinesis)
Telophase: Cell starts to divide nuclei form again in two new cells Followed by cytokinesis – division of
cytoplasm animal cell membrane “pinches” in plant cell forms a cell plate that becomes
the cell wallDivide!
(telophase)
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Interphase (again) DNA unwinds; cells separate now they can go back to doing their
every day jobs - GRRSNERT cycle starts over again
two 2n diploid cells
2 new smaller “daughter” cells
Get 2 exact copies of original cells
same DNA “clones”
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Mitosis in whitefish embryo
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Mitosis in plant cell
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onion root tip
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Overview of Cell Cycle
interphaseprophase
metaphase anaphase telophase
cytokinesis
I.P.M.A.T.C.
Please Make Another Two Cells
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When is mitosis a BAD thing When cells reproduce & they are not
needed these cells take over organs, but don’t
do the right job they just keep making copies “starve” other cells/tissues cancer – uncontrolled mitosis
damages organs
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Why would cells just make copies?
If DNA gets damaged, cells stop listening to correct instructions – make WRONG protein (enzymes) mutations – changes in DNA bases
Mutagens (carcinogens) – cause mutations:
UV radiation chemical exposure
benzene, toluene, asbestos
radiation exposure
cigarette smoke pollution age Genetics heat
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Tumors Benign tumor
abnormal cells remain at original site as a lump
most do not cause serious problems &can be removed by surgery
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Tumors Malignant tumor
cells leave original site - metastasizes carried by blood system to other tissues start more tumors
damage functions of organs throughout body
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Treatments for cancers Treatments kill rapidly dividing cells
chemotherapy poisonous drugs that kill rapidly dividing cells
radiation high energy beam kills rapidly dividing cells
surgery
side effects