Notes Cell Cycle 2010

8/6/2019 Notes Cell Cycle 2010

1/48

The Cell CycleMITOSIS:

Making New CellsMaking New DNA


2/48

Fromone cell tomany

Going from egg toorganism.the original fertilized egg has to divide

and divide

and divideand divide


3/48

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


4/48

The Big Challenge

Before division, a cell must make copies of

DNA

organelles

cell membrane lots ofothermolecules

Enzymes

Each new daughter cell requires acomplete set of genes.

Evenly divide these things between 2 new

(daughter) cells


5/48

The Big Picture

Loosely bound DNAis copied 2 copies of DNA wind up, line up, and

then split up.

One cell becomes

two


6/48

Chromosomes ofHumanFemale

46 chromosomes

23 pairs


7/48

Chromosomes ofHuman Male

46 chromosomes

23 pairs


8/48

Copying DNA

A dividing cell duplicates its DNA creates 2 copies of all DNA

separates the 2 copies toopposite ends of the

cell splits into 2 daughter cells

DNA starts loosely

wound in thenucleus

If you tried to divide

it like that, it could

tangle & break


9/48

Organizing &packaging DNA

nucleus

cell

DNA

nucleus

cell

4 chromosomes

in this organism

DNA in chromosomes in

everyday working cell

DNA in chromosomes in cell

getting ready to divide

DNA has been

wound up


10/48

DNA must be duplicated

nucleus

cell

DNA in chromosomes

nucleus

cell

duplicated chromosomes

chromosomes in cell

4single-stranded chromosomes

duplicated

chromosomes

4 double-stranded chromosomes


11/48

double-strandedhuman chromosomes

ready for mitosis


12/48

Some Chromosome Vocab

duplicated

chromosomes

Chromosome made upof

2 sister chromatids. DNAhas been replicated.

Centromere- regionwhere chromatids

are held together

Normal Cell Dividing Cell

Chromatin Loosely coiled

DNA. Disorganized, but

accessible to enzymes andproteins.


13/48

Use these words in a sentence that

conveys theirmeanings: chromosome,

chromatin, DNA, centromere

Use these words in a sentence thatconveys theirmeanings: mitosis,

growth, DNA replication, chromosome

Quizzam!!


14/48

DNA Replication


15/48


16/48

Copying DNA

Matching bases allowsDNA tobe easily copied


17/48

DNA replicationCopying DNA

replication

DNA starts as a double-stranded molecule

matching bases (A:T, C:G)

then it unzips

Helicase:

The unzippingenzyme


18/48

DNA replication

DNA

polymerase

Enzyme DNA polymerase

adds new bases

DNA bases

in nucleus


19/48


20/48

New copies ofDNA

Get 2 exact copies of DNA to split

between new cells

DNA

polymerase

DNA

polymerase


21/48

Copied & Paired Up Chromosomes

centromere


22/48

Copying DNA Semi-conservative

Each daughter strand is original DNA, new.


23/48

Copying DNA DNA Polymerase can only work in one

direction: 5 3

Can only add new nucleotides onto the sugar end

ofprevious one.

5

5

5

5

3

3

3

Base

Base

Base

Base


24/48

Copying DNA Leading strand: synthesized in 5 3

direction (continuous synthesis)

Lagging strand: synthesized in 3 5

direction. (Okazaki fragments.)

DNA strands

run inopposite

directions anti-parallel


25/48

Whats happening here?Quizzam!!


26/48

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 ittangle & break


27/48

The Cell Cycle: the period from the beginning ofone cell division to the beginning ofthe next cell division.

Interphase between celldivisions. Mosttime of the cell

cycle. Producematerials forgrowth

Prepare for the

next division Mitosis

cell division


28/48

The Cell Cycle

G0 phase: Whencells are notdividing

Mature cells.Ex:nerve cell, livercell

Can re-enter cell

cycle if thecorrect signalsare received.


29/48

Mitosis: Dividing DNA & cells

Stage 1: Prophase DNA winds into chromosomes (keeps it organized)

Nuclearmembrane breaks down

Spindle fibers form

nucleus

cell

duplicated

chromosomes


30/48


Stage 2: Metaphase chromosomes line up in middle

attached to spindle fibers that will help them

move

duplicated chromosomes

lined up in middle of cell


31/48


Stage 4: Anaphase Spindle fibers shorten, Chromosomes separate

start moving toopposite ends

One complete set of cells DNA is now at each end of

the cell.

chromosomes split &

move to opposite ends


32/48


Stage 5: Telophase reverse prophase

Nuclearmembrane forms

Chromosomes uncoil chromatin

Mitotic spindle breaks down


33/48


34/48

New daughter cells

Get 2 exact copies oforiginal cells

same DNA

clones


35/48

Cell division in Animals

Mitosis in whitefish embryo


36/48

onion root tip


37/48


38/48

Mitosis & Cancer:When Making New

CellsGoes TerriblyWrong!


39/48

When is mitosis a good thing?

When you have to add or replace cells

growth & development

repair

replacement


40/48

When is mitosis a BAD thing

When cells reproduce & they are not

needed

these cells take overorgans, but dont do

the right job they just keepmaking copies

cancer

damages organs


41/48

Control ofthe Cell Cycle

How does a healthy cell know when to divide? Cyclins proteins that regulate progression of a

cell through the cell cycle.

Checkpoints proteins detect problems at eachstepof the cell cycle. Initiate cell-cycle arrest if

problems are detected DNA mutations, incorrect attachment of spindlefibers to centromere

Proto-oncogenes Code for genes that initiate thecell cycle.

Have the potential tobecome oncogenes: cancer-causing genes.

Tumor suppressor genes code forproteins thatarrest, monitor, or slow the cell cycle.


42/48


How does a healthy cell knowwhen to divide? Attachment requirement cells mustbe able to attach to surroundingenvironment.

Space and nutrient requirements cells will only divide when they haveenough space and nutrition

Cancerous cells ignore these

requirements


43/48


If DNA gets damaged, cells stop listening

to correct instructions

mutations Causes ofmutations:

UV radiation

chemical exposure radiation exposure

heat

cigarette smoke

pollution age

Genetics

Viruses


44/48

Control ofthe Cell Cycle Cells usually require an accumulation of

several mutations before becoming cancerous Mutations toproto-oncogenes

Become over-active

Mutations to tumor suppressor genes

Become inactive

This explains why cancerbecome more likelyas a person gets older.

Genetic Predisposition: When a few mutations

are inherited, it becomes more likely thatcancer will develop. Fewermutations stillneeded.


45/48

Tumors

Benign tumor abnormal cells remain at original site as a

lump

most do not cause serious problems &

can be removed by surgery


46/48

Tumors

Malignant tumor cells leave original site

carried by blood system toother tissues

start more tumors

damage functions oforgans throughout body


47/48

Treatments forcancers

Treatments kill rapidly dividing cells chemotherapy

poisonous drugs that kill rapidly dividing cells

radiation high energy beam kills rapidly dividing cells

localized


48/48

Any Questions?

Notes Cell Cycle 2010

Documents