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