Regents Biology

Regents Biology

MITOSIS:Making New CellsMaking New DNA

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Where it all began…

You started as a cell smaller than a period at the end of a sentence…

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And now look at you…

How did you get from there to

here?

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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…

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Why do cells divide… One-celled organisms

for reproduction asexual reproduction (clones)

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

amoeba

starfish

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Dividing cells… What has to be copied

DNA organelles cell membrane lots of other

molecules enzymes

animal cellplant cell

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Copying DNA A dividing cell duplicates its DNA

creates 2 copies of all DNA separates the 2 copies to opposite ends

of the cell splits into 2 daughter cells

But the DNA starts loosely wound in the nucleus

If you tried to divide it like that, it could tangle & breaknucleus

cell

DNA

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Organizing & packaging DNA

nucleus

cell

DNA

nucleus

cell

chromosomesin this organism

DNA in chromosomes ineveryday “working” cell

DNA in chromosomes in cell getting ready to divide

DNA has been “wound up”

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Chromosome – condensed DNA bound in the center by a centromere

centromere

Chromatid – each strand of doubled chromosome

chromatidchromatin

Chromatin - condensed single strand DNA

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Chromosomes of Human Female

46 chromosomes23 pairs

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Chromosomes of Human Male

46 chromosomes23 pairs

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Copying & packaging DNA

Copying DNA

Coil DNA into compact chromosomes

When cell is ready to divide… copy DNA first, then… coil up doubled chromosomes

like thread on a spool… now can move DNA around cell without having

it tangle & break

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double-strandedhuman chromosomesready for mitosis

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DNA must be duplicated…

nucleus

cell

DNA in chromosomes

nucleus

cell

duplicated chromosomes

chromosomes in cell

4 single-stranded chromosomes

duplicatedchromosomes

4 double-stranded chromosomes

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Mitosis: Dividing DNA & cells Stage 1: cell copies DNA

nucleus

cell

DNA

(interphase)

• Cell growth

• DNA replicates

• Centrioles replicate and go to opposite sides of the cell

• Divided into 3 parts

• G1, S, G2

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Time Span

Cyclin A protein that determines the cell cycle Cyclin increases until it reaches a certain

point then cell starts mitosis

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Mitosis: Dividing DNA & cells Stage 2: DNA winds into chromosomes

DNA is wound up into chromosomes to keep it organized

nucleus

cell

duplicated chromosomes Wind up!

(prophase)

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Mitosis: Dividing DNA & cells Stage 3: Chromosomes line up

chromosomes line up in middle attached to protein “cables” that will

help them move

duplicated chromosomeslined up in middle of cell

Line up!

(metaphase)

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Mitosis: Dividing DNA & cells Stage 4: Chromosomes separate

chromosomes split, separating pairs start moving to opposite ends

chromosomes split & move to opposite ends

Separate!

(anaphase)

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Mitosis: Dividing DNA & cells Stage 5: Cell starts to divide

cells start to divide nucleus forms again

Divide!

(telophase)

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Mitosis: Dividing DNA & cells Stage 6: DNA unwinds again

cells separate now they can do their every day jobs

Bye Bye!

(cytokinesis)

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New “daughter” cells Get 2 exact copies of original cells

same DNA “clones”

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Cell division in Animals

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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 mitosis

interphase prophase

metaphase anaphase telophase

cytokinesis

I.P.M.A.T.C.

Please Make Another Two Cells

Regents Biology 2009-2010

Any Questions??

Any Questions??

Regents Biology

Asexual Reproduction

1. Binary Fission organism divides into

2 equal parts Ex: bacteria,

protozoan

2. Budding Parent divides into 2

unequal parts Ex: yeast, Hydra

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3. Spores Thickly coated

cells Ex: Mold

4. Regeneration Ability to regrow

lost body parts Ex: Planaria

5. Vegetative Propagation

Using roots, stems, and leaves to make a new plant

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Mitosis & Cancer:When Making New Cells

Goes Terribly Wrong!

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When is mitosis a good thing? When you have to add or replace cells

growth & development repair replacement

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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 cancer

damages organs

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Why would cells just make copies?

If DNA gets damaged, cells stop listening to correct instructions Mutations - carcinogens

Causes of mutations: UV radiation chemical exposure radiation exposure heat

cigarette smoke pollution age genetics

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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 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

side effects

Regents Biology 2009-2010

Any Questions??

Any Questions??