The Cell Cycle, Mitosis The Cell Cycle, Mitosis & Cell Division& Cell Division

Omnis cellula e cellulaOmnis cellula e cellula

Chapter 9 Biology In FocusChapter 9 Biology In Focus

AP Biology 2014AP Biology 2014

Ms. EggersMs. Eggers

Why?Why? From fertilization to arrival of baby, to From fertilization to arrival of baby, to

adulthood, we grow from one cell into trillions adulthood, we grow from one cell into trillions of cells. Why?of cells. Why?

Why arenWhy aren’’t we just one big cell? What limits cell t we just one big cell? What limits cell size?size?

What are the functions of cell division?What are the functions of cell division? ReproductionReproduction Growth and developmentGrowth and development Tissue repair and renewalTissue repair and renewal RegenerationRegeneration

Each of our cells is the same in one Each of our cells is the same in one way…way…

Every single cell in our body has the exact Every single cell in our body has the exact same set of genes – the blue print for same set of genes – the blue print for making an entire new organism (which making an entire new organism (which gives rise to the idea that someone could gives rise to the idea that someone could make a clone of you from a few of your make a clone of you from a few of your skin cells). skin cells).

The entire set of DNA in an organism is The entire set of DNA in an organism is called its called its genomegenome..

Division requires duplicationDivision requires duplication Every time a cell grows and divides, it Every time a cell grows and divides, it

must duplicate this set of blue prints (its must duplicate this set of blue prints (its genomegenome), so that each of the two cells ), so that each of the two cells produced (called produced (called daughter cellsdaughter cells) gets an ) gets an EXACT copy of what the EXACT copy of what the parent cellparent cell originally had.originally had.

This process of duplicating the genetic This process of duplicating the genetic blue print and then dividing into two new blue print and then dividing into two new cells is called cells is called cell divisioncell division..

The The cell cycle cell cycle is the life of a cell is the life of a cell from the time it is first formed from a from the time it is first formed from a dividing parent cell until its own dividing parent cell until its own division into daughter cells.division into daughter cells.

How is the DNA organized How is the DNA organized within our cells?within our cells?

The genetic The genetic information of a information of a eukaryotic eukaryotic organism is stored organism is stored in the in the nucleusnucleus of of the cell.the cell.

Within the nucleus are found Within the nucleus are found chromosomes…chromosomes…

ChromosomesChromosomes are are composed of composed of chromatinchromatin, which is a , which is a long, coiled strand of long, coiled strand of DNADNA and some and some proteins to help with proteins to help with structure.structure.

That long strand of That long strand of DNA contains DNA contains thousands of thousands of genesgenes – – each gene contains each gene contains the information to the information to make just one protein.make just one protein.

Chromosome structureChromosome structure

One arm of a duplicated chromosome

Where do we get our Where do we get our genes?genes?

Well, from Mom and Dad…Well, from Mom and Dad… So we have 2 copies of every gene – So we have 2 copies of every gene –

one from Mom and the other from Dad one from Mom and the other from Dad (a good back-up!)(a good back-up!)

Therefore, Therefore, we have 2 copies of we have 2 copies of every chromosome in our nucleus.every chromosome in our nucleus.

One pair of alike chromosomes are One pair of alike chromosomes are calledcalled homologous chromosomes. homologous chromosomes.

We have 46 chromosomes in We have 46 chromosomes in every every somaticsomatic (body) (body) cellcell… or … or

23 pairs.23 pairs. Two copies of chromosome # Two copies of chromosome #

1, # 2, # 3, etc.1, # 2, # 3, etc. There are 22 pairs of There are 22 pairs of

numbered chromosomes – numbered chromosomes – called called autosomesautosomes..

The last pair are called The last pair are called sex sex chromosomeschromosomes..

If your are female, you have If your are female, you have two copies of the X two copies of the X chromosome.chromosome.

If you are male, you have one If you are male, you have one X chromosome and one Y X chromosome and one Y chromosome.chromosome.

Our body cells are Our body cells are diploiddiploid..

Because our cells have 2 copies of each Because our cells have 2 copies of each type of chromosome, we refer to them type of chromosome, we refer to them as as diploiddiploid – and would write this as – and would write this as 2N2N..

Reproductive cells, called Reproductive cells, called gametesgametes, , only have one copy of each only have one copy of each chromosome (wechromosome (we’’ll talk about these ll talk about these later). We call these cells later). We call these cells haploidhaploid – and – and write this write this NN..

Different organisms have a Different organisms have a different number of different number of

chromosomes.chromosomes. The number of The number of

chromosomes an chromosomes an organism has bears no organism has bears no relation to its relation to its ““complexity.complexity.””

Having a different Having a different diploid number is also diploid number is also one of the reasons that one of the reasons that members of different members of different species cannot mate species cannot mate and produce fertile and produce fertile offspring.offspring.

OrganismOrganism Diploid Diploid Chromosome Chromosome ##

HumanHuman 4646

DogDog 7878

CatCat 3838

HorseHorse 6464

Cell divisionCell division

A parent cell divides A parent cell divides into 2 into 2 daughter daughter cellscells..

Then each daughter Then each daughter cell can divide again cell can divide again to form 2 daughter to form 2 daughter cells of their own.cells of their own.

Before division, a cell Before division, a cell must must growgrow, and it , and it must must duplicateduplicate its its chromosomes.chromosomes.

From the time a daughter cell From the time a daughter cell is is ““bornborn”” and divides again is and divides again is

called the called the cell cyclecell cycle..

Cytokinesis: when the membrane divides the cell into 2 separate cells

Parts of the cell cycleParts of the cell cycle CytokinesisCytokinesis: the division of the membrane and : the division of the membrane and

cytoplasm into two daughter cellscytoplasm into two daughter cells InterphaseInterphase: the cell grows, produces proteins : the cell grows, produces proteins

and cytoplasmic organellesand cytoplasmic organelles GG11 phase phase – the phase when cells are “doing their job”– the phase when cells are “doing their job” S phase S phase – chromosomes duplicate– chromosomes duplicate GG22 phase phase – completes preparations for cell division– completes preparations for cell division

MitosisMitosis: the division of the genetic material in : the division of the genetic material in the nucleusthe nucleus

What occurs in each stage What occurs in each stage of mitosis?of mitosis?

During the S phase, the During the S phase, the chromosomes have been chromosomes have been duplicated…duplicated…

In G2 there are now In G2 there are now centrosomescentrosomes, , which are the regions where the which are the regions where the microtubule spindles are organizedmicrotubule spindles are organized

ProphaseProphase:: Chromosomes Chromosomes

condensecondense Sister chromatids Sister chromatids

become apparentbecome apparent Nucleoli disappearNucleoli disappear Mitotic spindle Mitotic spindle

forms, centrosomes forms, centrosomes appear as asters appear as asters and begin to and begin to separateseparate

PrometaphasePrometaphase:: Nuclear membrane Nuclear membrane

fragmentsfragments Chromosomes become Chromosomes become

even more condensedeven more condensed Kinetochores form at the Kinetochores form at the

centromere of each centromere of each chromosomechromosome

Mitotic spindles now Mitotic spindles now extend across the cell extend across the cell and meetand meet

Microtubule spindles Microtubule spindles attach to the attach to the kinetochoreskinetochores

ProphaseProphase PrometaphasePrometaphase

MetaphaseMetaphase:: Chromosomes line up Chromosomes line up

in “single file” on the in “single file” on the metaphase platemetaphase plate

Centrosomes are at Centrosomes are at either side of the celleither side of the cell

Kinetochore Kinetochore microtubules are microtubules are connected to each connected to each chromosome at the chromosome at the centromerecentromere

AnaphaseAnaphase:: Cohesion proteins holding Cohesion proteins holding

the two sister chromatids the two sister chromatids together at the together at the centromere are cleavedcentromere are cleaved

The mitotic spindles The mitotic spindles begin to shorten, pulling begin to shorten, pulling each new individual each new individual daughter chromosome to daughter chromosome to opposite ends of the cellopposite ends of the cell

This is the shortest phase This is the shortest phase

MetaphaseMetaphase AnaphaseAnaphase

TelophaseTelophase Two nulcei reformTwo nulcei reform Nucleoli reappearNucleoli reappear Chromosomes Chromosomes

decondensedecondense Mitotic spindles Mitotic spindles

disassemble and disassemble and disappeardisappear

CytokinesisCytokinesis In animal cells this In animal cells this

involves the involves the development of a development of a cleavage furrow cleavage furrow created by a ring of created by a ring of microfilamentsmicrofilaments

In plant cells, a cell In plant cells, a cell plate forms plate forms between the two between the two daughter cells and daughter cells and eventually becomes eventually becomes the new cell wallthe new cell wall

Telophase Telophase CytokinesisCytokinesis

Mitosis Animations, etc.Mitosis Animations, etc.

Mitosis video 1 (6:20)Mitosis video 1 (6:20) Mitosis Rap (3:17)Mitosis Rap (3:17)

Binary Fission Binary Fission in Bacteriain Bacteria

Reproduction in bacteria Reproduction in bacteria involves duplicating their involves duplicating their bacterial chromosome, bacterial chromosome, enlarging, and dividingenlarging, and dividing

It does NOT involve the It does NOT involve the exchange of genetic exchange of genetic material that occurs in material that occurs in eukaryotic sexual eukaryotic sexual reproductionreproduction

The new bacterium is The new bacterium is identical to the original identical to the original bacteriumbacterium

Videos of actual mitosis (tutorial Videos of actual mitosis (tutorial videos can be found on my videos can be found on my

Weebly site)Weebly site)

Mitosis in developing sea urchin cellsMitosis in developing sea urchin cells Contrast microscopy video of mitosisContrast microscopy video of mitosis Fluorescent microscopy video of Fluorescent microscopy video of

mitosis in early developing fruit fly mitosis in early developing fruit fly embryoembryo

Binary fission in bacteria videoBinary fission in bacteria video