MITOSIS: Making New Cells Making New DNA

Where it all began… You started as a cell smaller than a period at the end of a sentence…

How did you get from there to here? And now look at you… How did you get from there to here?

Getting from there to here… Going from egg to baby…. the original fertilized egg has to divide… and divide…

Why do cells divide… One-celled organisms Multi-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 Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents

Dividing cells… What has to be copied DNA organelles cell membrane lots of other molecules enzymes plant cell animal cell

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 & break DNA cell nucleus

Organizing & packaging DNA cell nucleus DNA has been “wound up” DNA in chromosomes in everyday “working” cell cell nucleus chromosomes in this organism DNA in chromosomes in cell getting ready to divide

Chromatin - condensed single strand DNA Chromosome – condensed DNA bound in the center by a centromere centromere chromatin chromatid Chromatin - condensed single strand DNA Chromatid – each strand of doubled chromosome

Chromosomes of Human Female 23 pairs

Chromosomes of Human Male 23 pairs

Copying & packaging DNA 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 Copying DNA Coil DNA into compact chromosomes

double-stranded human chromosomes ready for mitosis

DNA must be duplicated… chromosomes in cell 4 single-stranded chromosomes nucleus cell DNA in chromosomes nucleus cell duplicated chromosomes duplicated chromosomes 4 double-stranded chromosomes

Mitosis: Dividing DNA & cells Stage 1: cell copies DNA Cell growth DNA replicates Centrioles replicate and go to opposite sides of the cell Divided into 3 parts G1, S, G2 DNA cell nucleus (interphase)

Time Span Cyclin A protein that determines the cell cycle Cyclin increases until it reaches a certain point then cell starts mitosis

Mitosis: Dividing DNA & cells Stage 2: DNA winds into chromosomes DNA is wound up into chromosomes to keep it organized duplicated chromosomes Wind up! cell nucleus (prophase)

Mitosis: Dividing DNA & cells Stage 3: Chromosomes line up chromosomes line up in middle attached to protein “cables” that will help them move Line up! duplicated chromosomes lined up in middle of cell (metaphase)

Mitosis: Dividing DNA & cells Stage 4: Chromosomes separate chromosomes split, separating pairs start moving to opposite ends Separate! chromosomes split & move to opposite ends (anaphase)

Mitosis: Dividing DNA & cells Stage 5: Cell starts to divide cells start to divide nucleus forms again Divide! (telophase)

Mitosis: Dividing DNA & cells Stage 6: DNA unwinds again cells separate now they can do their every day jobs Bye Bye! (cytokinesis)

New “daughter” cells Get 2 exact copies of original cells same DNA “clones”

Cell division in Animals

Mitosis in whitefish embryo

Mitosis in plant cell

onion root tip

Please Make Another Two Cells I.P.M.A.T.C. Overview of mitosis interphase prophase Please Make Another Two Cells cytokinesis metaphase anaphase telophase

Any Questions?? 2009-2010

Asexual Reproduction Binary Fission Budding organism divides into 2 equal parts Ex: bacteria, protozoan Budding Parent divides into 2 unequal parts Ex: yeast, Hydra

Vegetative Propagation Spores Thickly coated cells Ex: Mold Regeneration Ability to regrow lost body parts Ex: Planaria Vegetative Propagation Using roots, stems, and leaves to make a new plant

Mitosis & Cancer: When Making New Cells Goes Terribly Wrong!

When is mitosis a good thing? When you have to add or replace cells growth & development repair replacement

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

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

Tumors Benign tumor abnormal cells remain at original site as a lump most do not cause serious problems & can be removed by surgery

Tumors Malignant tumor cells leave original site carried by blood system to other tissues start more tumors damage functions of organs throughout body

Treatments for cancers side effects Treatments for cancers Treatments kill rapidly dividing cells chemotherapy poisonous drugs that kill rapidly dividing cells radiation high energy beam kills rapidly dividing cells

Any Questions?? 2009-2010