The Cell Cycle

The Cell CycleThe Cell Cycleand and

ReproductionReproduction

The Cell CycleThe Cell Cycle

Like all living things, cells must be able to Like all living things, cells must be able to grow and reproduce.grow and reproduce.

This happens during the cell cycle. The This happens during the cell cycle. The cell cycle is divided into two parts:cell cycle is divided into two parts:

• Cell Growth (Interphase)Cell Growth (Interphase)

• Cell Division (Mitosis)Cell Division (Mitosis)

The ChromosomeThe Chromosome

http://www.biologycorner.com/resources/chromosome-labeled.gif www.sciencelearn.org.nz/var/sciencelearn/stor...

The Cell Cycle cont.The Cell Cycle cont.

The longest part of the cell cycle is called The longest part of the cell cycle is called interphase. It is divided into 3 main parts:interphase. It is divided into 3 main parts: G1 stageG1 stage- (1- (1stst Growth stage)- the cell grows Growth stage)- the cell grows

and develops; new proteins are made.and develops; new proteins are made. S stageS stage- (Synthesis stage)- the chromosomes - (Synthesis stage)- the chromosomes

replicate in the nucleus to form a new set of replicate in the nucleus to form a new set of identical chromosomesidentical chromosomes

G2 stageG2 stage- The cell is getting ready to divide. - The cell is getting ready to divide. RNA and proteins are made. Organelles are RNA and proteins are made. Organelles are duplicated.duplicated.

The Cell Cycle, cont.The Cell Cycle, cont.

The M phase (Mitosis) is the process of The M phase (Mitosis) is the process of nuclear division.nuclear division.

There are 4 stages of MitosisThere are 4 stages of Mitosis ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase

The Cell Cycle, cont.The Cell Cycle, cont.

Mitosis is the process of nuclear divisionMitosis is the process of nuclear division

Mitosis is also important because it allows Mitosis is also important because it allows tissues to repair themselves by producing tissues to repair themselves by producing new cells.new cells.


1. 1. ProphaseProphase Chromatin coils up, Chromatin coils up,

shortens, and shortens, and thickens.thickens.

Nuclear membrane Nuclear membrane dissolvesdissolves

Spindle starts to Spindle starts to formform

http://www.macroevolution.net/images/prophase.jpg


2. 2. MetaphaseMetaphase Chromosomes Chromosomes

attach to the attach to the spindle fibers by spindle fibers by the centromere. the centromere.

Chromosomes line Chromosomes line up at the equator of up at the equator of the nucleus. the nucleus.

Meta = MiddleMeta = Middlehttp://med.mui.ac.ir/slide/genetic/metaphase.jpg


3. 3. AnaphaseAnaphase The chromosomes The chromosomes

are in pairs and are are in pairs and are pulled apart by the pulled apart by the spindle fibers.spindle fibers.

Looks like an “X” Looks like an “X” that is being pulled that is being pulled apart.apart.

http://micro.magnet.fsu.edu/micro/gallery/mitosis/earlyanaphase.jpg


4. 4. TelophaseTelophase Chromosomes Chromosomes

have reached the have reached the opposite ends of opposite ends of the cell.the cell.

Opposite of Opposite of Prophase! Prophase! Everything done in Everything done in prophase is prophase is undone in undone in telophase.telophase.

http://www.bioweb.uncc.edu/1110Lab/notes/notes1/labpics/Animal%20Telophase%20(Google).jpg


After telophase is finished, the cytoplasm After telophase is finished, the cytoplasm is divided during the process of is divided during the process of cytokinesis.cytokinesis.

Cyto- means “Cell” -kinesis means “to cut”Cyto- means “Cell” -kinesis means “to cut” Interphase- G1- begins again at the end of Interphase- G1- begins again at the end of

cytokinesiscytokinesis


In plant cells, a cell In plant cells, a cell plate is formed down plate is formed down the equator of the cell the equator of the cell to divide the cell in to divide the cell in half. The cell plate will half. The cell plate will become the cell wall become the cell wall between the two new between the two new identical cells.identical cells.

http://iknow.net/images/screen_cellplate_512.jpg


In animal cells, the In animal cells, the cell membrane begins cell membrane begins to “pinch” in at the to “pinch” in at the end of telophase end of telophase creating 2 new creating 2 new identical cells.identical cells.

This indention is This indention is called cleavage called cleavage furrow. furrow.

http://www.dkimages.com/discover/previews/801/908016.JPG

http://education.kings.edu/dsmith/cytokinesis.gif

RememberRemember

PMATPMAT

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophase

Sexual Reproduction and MeiosisSexual Reproduction and Meiosis

Organisms using sexual reproduction have Organisms using sexual reproduction have 2 types of cells:2 types of cells: 1. 1. Somatic CellsSomatic Cells- Body Cells- Body Cells 2. 2. GametesGametes- Sex Cells- Sex Cells

**Sex Cells are reproduced by a process **Sex Cells are reproduced by a process called MEIOSIS**called MEIOSIS**


When you see Meiosis you should When you see Meiosis you should think “Sex”. think “Sex”.

Male cells (sperm cells) and Female Male cells (sperm cells) and Female cells (Egg cells) are used in the cells (Egg cells) are used in the process of Meiosis.process of Meiosis.


Male Cells (Sperm Cells)Male Cells (Sperm Cells) Sperm cells are produced in the testes and Sperm cells are produced in the testes and

are released through the penis.are released through the penis. Sperm begin reproduction at puberty and Sperm begin reproduction at puberty and

continue until death.continue until death. It takes 72 hours for a cell to reach maturity.It takes 72 hours for a cell to reach maturity. 400-500 million sperm are released each 400-500 million sperm are released each

ejaculation.ejaculation.


Male cells….(cont.)Male cells….(cont.) Sperm can build up over time and must be Sperm can build up over time and must be

released. Some dribble out and are released released. Some dribble out and are released during urination. Some may be reabsorbed during urination. Some may be reabsorbed into the body.into the body.

Sperm require temperatures of about 5 Sperm require temperatures of about 5 degrees cooler than the body. That’s why the degrees cooler than the body. That’s why the testes hang outside the body.testes hang outside the body.

A change in temp. will cause the testes to A change in temp. will cause the testes to draw closer to the body for warmth or get draw closer to the body for warmth or get really lose when it gets hot.really lose when it gets hot.


Female sex cells are called eggs.Female sex cells are called eggs. Eggs are produced in the ovaries.Eggs are produced in the ovaries. Egg production begins at birth in females but Egg production begins at birth in females but

the eggs are not released until the onset of the eggs are not released until the onset of menstruation.menstruation.

Egg production stops at menopause.Egg production stops at menopause. Ovaries contain thousands of eggs.Ovaries contain thousands of eggs. Only one egg is released each month in Only one egg is released each month in

humans.humans.


Female sex cells….(cont.)Female sex cells….(cont.) Before ovulation (releasing an egg) the uterus Before ovulation (releasing an egg) the uterus

swells with blood and become a nice thick swells with blood and become a nice thick pillow for the prospective baby.pillow for the prospective baby.

When fertilization does not take place, the When fertilization does not take place, the lining of the uterus, the egg, and all the extra lining of the uterus, the egg, and all the extra blood must be removed from the body. This blood must be removed from the body. This takes place during the menstrual cycle.takes place during the menstrual cycle.


Chromosome NumberChromosome Number The normal number of chromosomes an The normal number of chromosomes an

organism is supposed to have is referred to organism is supposed to have is referred to as diploid (2n).as diploid (2n).

Haploid (n) is half the number of Haploid (n) is half the number of chromosomes.chromosomes.

Sex cells are haploid and body cells are Sex cells are haploid and body cells are always diploid.always diploid.


Chromosome number (cont.)Chromosome number (cont.) Chromosomes exist in pairs (homologous Chromosomes exist in pairs (homologous

chromosomes. Humans have 23 pair of chromosomes. Humans have 23 pair of chromosomes which equals 46.chromosomes which equals 46.

The diploid number for humans body cells is The diploid number for humans body cells is 46. 46.

The haploid number for human sex cells is 23.The haploid number for human sex cells is 23.• Eggs have 23 chromosomesEggs have 23 chromosomes• Sperm cells have 23 chromosomesSperm cells have 23 chromosomes• Skin cells have 46 chromosomes.Skin cells have 46 chromosomes.


Chromosome number…(cont.)Chromosome number…(cont.) Meiosis therefore produces haploid cells.Meiosis therefore produces haploid cells. Meiosis adds genetic variation.Meiosis adds genetic variation. Chromosomes separate randomly and get Chromosomes separate randomly and get

“mixed up” therefore it adds variation to the “mixed up” therefore it adds variation to the way organisms look. For example, you and way organisms look. For example, you and your siblings were made by the 2 same your siblings were made by the 2 same parents but are genetically different.parents but are genetically different.

Stages of MeiosisStages of Meiosis

Meiosis IMeiosis I It is very similar to It is very similar to

MitosisMitosis Meiosis I results in 2 Meiosis I results in 2

identical cellsidentical cells The 4 stages of The 4 stages of

Meiosis I are:Meiosis I are:• Prophase IProphase I• Metaphase IMetaphase I• Anaphase IAnaphase I• Telophase ITelophase I

Meiosis IIMeiosis II End product is 4 cells End product is 4 cells

with half the number of with half the number of chromosomeschromosomes

Stages of Meiosis II Stages of Meiosis II are:are:

• Prophase IIProphase II• Metaphase IIMetaphase II• Anaphase IIAnaphase II• Telophase IITelophase II

Mitosis vs. MeiosisMitosis vs. Meiosis

MitosisMitosis MeiosisMeiosis

Makes Body CellsMakes Body Cells Makes Sex CellsMakes Sex Cells

Makes diploid cellsMakes diploid cells Makes haploid cellsMakes haploid cells

1 Division1 Division 2 Divisions2 Divisions

Occurs in most all living thingsOccurs in most all living things Occurs only in organisms that Occurs only in organisms that perform sexual reproductionperform sexual reproduction

Types of ReproductionTypes of Reproduction

Reproduction is an essential part of the Reproduction is an essential part of the characteristics of life.characteristics of life.

Assures the continuation of the speciesAssures the continuation of the species An organisms adaptations and drives are An organisms adaptations and drives are

for one purpose: reproductionfor one purpose: reproduction An organism is only successful if it can An organism is only successful if it can

reproducereproduce


There are 2 types of reproduction:There are 2 types of reproduction: 1. Sexual Reproduction1. Sexual Reproduction Examples:Examples:

• Egg and sperm (haploid) meet and create a new Egg and sperm (haploid) meet and create a new organism (diploid)organism (diploid)

• Pollen fertilizing an eggPollen fertilizing an egg• Female frog lays eggs in the water and the male Female frog lays eggs in the water and the male

sprays sperm all over them (external fertilization).sprays sperm all over them (external fertilization).• Sperm is deposited into the female’s vagina by the Sperm is deposited into the female’s vagina by the

penis (internal fertilization).penis (internal fertilization).


2. Asexual Reproduction2. Asexual Reproduction Comes from 1 parentComes from 1 parent Produces genetically identical offspring (clones)Produces genetically identical offspring (clones) There is NO halving of the chromosomesThere is NO halving of the chromosomesTypes of Asexual ReproductionTypes of Asexual Reproductiona. a. Binary FissionBinary Fission- a single cell splits in half. Common in - a single cell splits in half. Common in

bacteria and some protists.bacteria and some protists.b. b. BuddingBudding- small areas of cells that begin to grow into a - small areas of cells that begin to grow into a

new, separate organism. Used by fungi and simple new, separate organism. Used by fungi and simple animals.animals.

c. c. Vegetative propagationVegetative propagation-plants send runners out that -plants send runners out that grow into a new plant or cuttings can be taken from a grow into a new plant or cuttings can be taken from a plant and grown.plant and grown.

The Cell Cycle

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Transcript of The Cell Cycle