Cell ReproductionCell Reproduction

Starting at the beginning…Starting at the beginning…

Biologically Biologically speaking, where speaking, where did YOU come did YOU come from?from?

CellsCells

How many cells How many cells make up a human make up a human body?body?

Did you have the Did you have the same number last same number last year? What about year? What about when you were 2 when you were 2 years old? 2 years old? 2 months old?months old?

CellsCells

Your body is made Your body is made up of between 10 up of between 10 and 100 trillion cells. and 100 trillion cells. (100,000,000,000,0(100,000,000,000,000)00)

One-thousandth of One-thousandth of them die every daythem die every day

CellsCells

Where do all these cells come from?Where do all these cells come from?

Cell SpecializationCell Specialization

Different body cells Different body cells perform different perform different functionsfunctions

Examples: skin, Examples: skin, nerve, red blood nerve, red blood cells, liver cells, cells, liver cells, plateletsplatelets

Cell SpecializationCell Specialization

Different cells live for different amounts of Different cells live for different amounts of timetime

Cellular ReproductionCellular Reproduction

New cells are made New cells are made from copies of old from copies of old cellscells

This process began This process began occurring before occurring before you were born and you were born and will continue until will continue until after you dieafter you die

Types of Cellular Types of Cellular ReproductionReproduction

MITOSIS – results in MITOSIS – results in two identical cells; two identical cells; used for the used for the majority of cells in majority of cells in the bodythe body

MEIOSIS – results in MEIOSIS – results in four cells that are four cells that are different from the different from the “parents”; used for “parents”; used for sex cells onlysex cells only

MitosisMitosis

Results in body Results in body growth or body growth or body repairrepair

Two new cells are Two new cells are called “daughter called “daughter cells”cells”

A Review of Cell FeaturesA Review of Cell Features

Cell MembraneCell Membrane CytoplasmCytoplasm NucleusNucleus Nuclear MembraneNuclear Membrane Chromosomes – strands Chromosomes – strands

that carry a cell’s DNAthat carry a cell’s DNA Centrioles – strong, Centrioles – strong,

barrell-shaped organellebarrell-shaped organelle

MitosisMitosis

Goals – duplicate chromosomes and Goals – duplicate chromosomes and move them to two new daughter move them to two new daughter cellscells

Before Mitosis BeginsBefore Mitosis Begins

Chromosomes are Chromosomes are duplicated within the duplicated within the cells (exact copies)cells (exact copies)

Held together at centerHeld together at center

Two strands are called Two strands are called “sister chromatids”“sister chromatids”

MitosisMitosis

Step 1: Step 1: PROPHASEPROPHASE– Sister chromatids Sister chromatids

thickenthicken– Nuclear membrane Nuclear membrane

breaks downbreaks down– Two centrioles move Two centrioles move

apartapart– Fibers (strands of Fibers (strands of

protein) form between protein) form between centriolescentrioles

MitosisMitosis

Step 2: Step 2: METAPHASEMETAPHASE– Centrioles to Centrioles to

opposite ends of opposite ends of cellcell

– Fibers stretch Fibers stretch betweenbetween

– Sister chromatids Sister chromatids attach to fibersattach to fibers

– Sister chromatids Sister chromatids line up at center of line up at center of the cellthe cell

MitosisMitosis

Step 3: ANAPHASEStep 3: ANAPHASE– Sister chromatids Sister chromatids

pulled apart from pulled apart from partnerpartner

– Fibers pull chromatids Fibers pull chromatids towards centrioles at towards centrioles at opposite ends of the opposite ends of the cellcell

MitosisMitosis

STEP 4: STEP 4: TELOPHASETELOPHASE– Each side now has Each side now has

complete set of complete set of chromosomeschromosomes

– Fibers disappearFibers disappear– Nuclear membrane re-Nuclear membrane re-

formsforms– Cell membrane pinches Cell membrane pinches

inwards to form 2 cellsinwards to form 2 cells

Mitosis in Plant CellsMitosis in Plant Cells

2 Differences2 Differences– No centriolesNo centrioles– Cell wall must re-Cell wall must re-

form between new form between new cellscells

INTERPHASEINTERPHASE

ANAPHASE

TELOPHASE

PROPHASE

METAPHASE

Importance of Importance of ChromosomesChromosomes

All chromosomes come in All chromosomes come in pairspairs

Humans have 23 pairs, so Humans have 23 pairs, so a normal cell has 46 a normal cell has 46 chromosomeschromosomes

All cells need a full set to All cells need a full set to function properly (except function properly (except sex cells)sex cells)

Chromosome NumberChromosome Number

Before mitosis begins, cells Before mitosis begins, cells have two of each have two of each chromosome (2N)chromosome (2N)

After chromosomes After chromosomes duplicate, cells have four of duplicate, cells have four of each chromosome (4N)each chromosome (4N)

After mitosis, cells have After mitosis, cells have two of each chromosome two of each chromosome (2N)(2N)

MeiosisMeiosis

MeiosisMeiosis Process that creates gametes (eggs and Process that creates gametes (eggs and

sperm)sperm)

Cells divide twiceCells divide twice

Chromosome NumberChromosome Number Cells start with two of Cells start with two of

each chromosome each chromosome (2N)(2N)

Chromosomes double Chromosomes double (4N)(4N)

Pairs divide (2N)Pairs divide (2N)

Sister chromatids Sister chromatids divide (N)divide (N)

Importance of MeiosisImportance of Meiosis

During fertilization, During fertilization, sperm (N) and egg sperm (N) and egg (N) fuse to create (N) fuse to create one cell (2N)one cell (2N)

New cell has New cell has complete set of complete set of chromosomes (half chromosomes (half from mother, half from mother, half from father)from father)

Chromosome NumberChromosome Number

N represents number of PAIRS of N represents number of PAIRS of chromosomeschromosomes

2N = total number of chromosomes 2N = total number of chromosomes in a normal cellin a normal cell

N – total number of chromosomes in N – total number of chromosomes in a gamete (sex cell)a gamete (sex cell)

Steps of MeiosisSteps of Meiosis

Step 1Step 1– PROPHASE IPROPHASE I

Steps of MeiosisSteps of Meiosis

Step 2:Step 2:– METAPHASE IMETAPHASE I

Steps of MeiosisSteps of Meiosis Step 3:Step 3:

– ANAPHASE IANAPHASE I Sister chromatids DO Sister chromatids DO

NOT separate.NOT separate.

– TELEPHASE ITELEPHASE I

Steps of MeiosisSteps of Meiosis

Step 4:Step 4:– PROPHASE IIPROPHASE II– Cell has been split Cell has been split

in twoin two– No nuclear No nuclear

membrane formsmembrane forms

Steps of MeiosisSteps of Meiosis

Step 5:Step 5:– Occurs in both cellsOccurs in both cells– METAPHASE IIMETAPHASE II

Steps of MeiosisSteps of Meiosis

Step 6:Step 6:– ANAPHASE IIANAPHASE II– TELEPHASE IITELEPHASE II

THE MOST IMPORTANT THE MOST IMPORTANT DIFFERENCEDIFFERENCE

In the first cell division, In the first cell division, CHROMOSOME PAIRS are pulled CHROMOSOME PAIRS are pulled apart.apart.

In the second cell division, SISTER In the second cell division, SISTER CHROMATIDS are pulled apart.CHROMATIDS are pulled apart.

Cancer and AgingCancer and Aging

Cancer/AgingCancer/Aging How are cancer and aging similar?How are cancer and aging similar?

Cancer/AgingCancer/Aging

Changes in rates of mitosisChanges in rates of mitosis

AgingAging

What properties of What properties of a person’s body a person’s body change as they change as they age?age?

Physically? Physically? Physiologically?Physiologically?

CancerCancer

Rapid, abnormal, Rapid, abnormal, uncontrolled uncontrolled mitosismitosis

What causes What causes cancer?cancer?

Cancer CausesCancer Causes

VirusesViruses ChemicalsChemicals RadiationRadiation