Mitosis Notes

2

Cell DivisionCell Division All cells are derived from All cells are derived from pre-pre-

existingexisting cells cells New cells are produced for New cells are produced for

growthgrowth and to and to replace damaged replace damaged or or old cellsold cells

Differs in Differs in prokaryotes (bacteriaprokaryotes (bacteria) ) and and eukaryotes (protists, fungi, eukaryotes (protists, fungi, plants, & animals)plants, & animals)

3

Keeping Cells Keeping Cells IdenticalIdentical

The instructions for The instructions for making cell parts making cell parts are encoded in are encoded in the DNA, so each the DNA, so each new cell must get new cell must get a complete set of a complete set of the DNA the DNA moleculesmolecules

4

DNA ReplicationDNA Replication DNA must be DNA must be

copied or copied or replicated before replicated before cell division cell division

Each new cell Each new cell will then have an will then have an identical copy of identical copy of the the DNADNA

Original DNA Original DNA strandstrand

Two new, Two new, identical DNA identical DNA strandsstrands

Mitosis NotesCells divide to make more cells…

this is called mitosis. All organisms start as just one

cell and continue to divide and make more. Humans have over 50,000,000,000,000 cells.

Mitosis Mitosis is the division of the nucleus in

eukaryotic cells. Mitosis has 6 steps. In mitosis the DNA is copied so that each

cell gets a copy. The DNA is condensed into a

chromosome. Humans have 46 chromosomes.

Chromosomes Notes Each of the cells in your body have the

same 46 chromosomes. You get 23 chromosomes from each parent.

Not all species have the same number of chromosomes. Corn has 20, flies have 10, chimpanzees have 48.

Chromosome Notes Each chromosomes has a central region

called a centromere that is an important attachment point for mitosis.

Chromosome Notes The cell providing the

DNA to be copied is the “parent cell,” the cells that are created are identical “daughter cell.”

Chromosome A chromosome contains

the DNA for the organism.

During mitosis the chromosome divides into two chromatids that are copied during mitosis.

These chromatids are “sister chromatids”

11

KaryotypeKaryotype First 22 pairs are

called autosomes Last pair are the sex

chromosomes XX female or XY male

12

Boy or Girl?Boy or Girl?

Y - ChromosomeY - Chromosome

X - ChromosomeX - Chromosome

The Y Chromosome DecidesThe Y Chromosome Decides

13

Prokaryotic Prokaryotic ChromosomeChromosome

The DNA of The DNA of prokaryotes prokaryotes (bacteria) is (bacteria) is one, circular one, circular chromosome chromosome attached to the attached to the inside of the inside of the cell membranecell membrane

14

Cell Division in Cell Division in ProkaryotesProkaryotes Prokaryotes such as

bacteria divide into 2 identical cells by the process of binary fission

Single chromosome makes a copy of itself

Cell wall forms between the chromosomes dividing the cell

Parent cellParent cell

2 identical daughter cells2 identical daughter cells

Chromosome Chromosome doublesdoubles

Cell splitsCell splits

15

Types of Cell Types of Cell ReproductionReproduction

Asexual reproduction Asexual reproduction involves a involves a single cell single cell dividing to make dividing to make 2 new, identical daughter 2 new, identical daughter cellscells

MitosisMitosis & & binary fission binary fission are examples of are examples of asexual reproductionasexual reproduction

Sexual reproduction Sexual reproduction involves involves two cells two cells ((egg egg & sperm& sperm) joining to make a new cell ) joining to make a new cell ((zygotezygote) that is ) that is NOT identical NOT identical to the original to the original cellscells

MeiosisMeiosis is an example is an example

The cell cycle Some cells divide constantly like skin cells

and stomach cells. Some cells divide only every 10 years. Actively dividing cells go through the cell cycle. The cell cycle has four parts.

The Cell Cycle G1- (GAP) Each chromosome has 1

chromatid. Cells spend most of their time here if they are not dividing.

S- (Synthesis) this is when DNA is copied. The chromosome goes from one chromatid to 2 chromatids.

G2- Is the period between S and mitosis. The cell prepares for Mitosis

M- is Mitosis

18

Daughter Daughter CellsCells

DNA CopiedDNA Copied

Cells Cells MatureMature

Cells prepare for DivisionCells prepare for Division

Cell Divides into Identical cellsCell Divides into Identical cells

Interphase During Interphase chromosomes are

copied (sister chromosome) but remain in loose structures called chromatin.

All the organelles are copied. Interphase is not technically part of mitosis

because mitosis is division of the nucleus and Interphase involves division of other organelles.

Prophase Prophase means “the before stage.”

Prophase is the start of mitosis. Chromatin condenses into chromosomes. The microtubules condense into

centrisomes which move to opposite poles of the cell.

The nuclear membrane starts to dissolve. Spindle fibers begin to form to help line the

chromosomes up.

Metaphase Chromosomes line up on the equator of the

cell. Spindle fibers attach to the centromeres of the chromatids.

Everything is now aligned for the rest of division to occur.

Anaphase Chromatids (or pairs of chromosomes)

separate and move to opposite ends of the cell.

The spindle fibers contract and the chromosomes are pulled towards the centrioles.

Telophase In telophase the cell divides. Two new

nuclei begin to form. The chromosomes are at the poles and the

spindle fibers disintegrate. Chromosomes begin to appear as

chromatin (the threads not the rods). This is the end of mitosis.

Cytokinesis The organelles get divided evenly into each

(daughter cell). Each cell has identical chromosomes in their own nucleus.

Plant and animal cells divide differently. Plants form a new cell wall that cuts the two cells apart. Animal cells form actin fibers around the equator of the cell and this pinches the cell in half.

Cytokinesis isn’t part of mitosis (doesn’t involve the nucleus). After Cytokinesis we go back to G1 and start over.

White Board Mitosis Review

What part of mitosis is shown?

What part of mitosis is shown?

What part of mitosis is shown?

What part of mitosis is shown?

What part of mitosis is shown?

In what part of mitosis do chromosomes double?

In what part of mitosis do chromosomes attach to spindle

fibers?

In what part of mitosis does the nuclear membrane start to re-form?

In what part of mitosis do the chromosomes line up at the cell

equator?

When do the copied chromosomes move to opposite ends of the cell?