ChromosomesChromosomesand and CellCell

ReproductionReproduction

Chromosome Structure

ChromosomesChromosomes are the coiled are the coiled up version of DNA.up version of DNA.

They consist of DNA and They consist of DNA and proteins: proteins: histoneshistones and and nonhistonesnonhistones

Chromosome Packing Animation

Point of Confusion: Chromatin Point of Confusion: Chromatin vs. Chromatid vs. Chromosomevs. Chromatid vs. Chromosome

What is the Difference???What is the Difference???

centromere

sister chromatids

single-strandedchromosomes

double-strandedchromosomes

Chromatids are attached at the Chromatids are attached at the center called a center called a centromerecentromere..

Sister Chromatids

What is a Kinetochore?What is a Kinetochore?

Kinetochore Animation

Centrosome & Centrioles Centrosome & Centrioles oh the definitions…oh the definitions…

Centrioles: ANIMAL CELLS ONLYCentrioles: ANIMAL CELLS ONLYNonmembrane-bound organelles that occur in pairs just outside the Nonmembrane-bound organelles that occur in pairs just outside the nucleus of animal cells. Each centriole is composed of a cylinder or nucleus of animal cells. Each centriole is composed of a cylinder or ring of 9 sets of microtubule triplets with none in the middle (9 + 0 ring of 9 sets of microtubule triplets with none in the middle (9 + 0 pattern). During cell division a pair of centrioles moves to each end of pattern). During cell division a pair of centrioles moves to each end of the cell, forming the poles of the mitotic spindle. Centrioles also give the cell, forming the poles of the mitotic spindle. Centrioles also give rise to basal bodies that control the origin of cilia and flagella in motile rise to basal bodies that control the origin of cilia and flagella in motile cells of protists. In cross section, flagella and cilia have 9 sets of cells of protists. In cross section, flagella and cilia have 9 sets of microtubule doublets surrounding a pair of single microtubules in the microtubule doublets surrounding a pair of single microtubules in the center (9 + 2 pattern). This characteristic pattern also occurs in motile center (9 + 2 pattern). This characteristic pattern also occurs in motile cells of higher organisms, such as human sperm.cells of higher organisms, such as human sperm.

Centrosome:Centrosome:In animal cells the centrosome includes a pair of centrioles surrounded In animal cells the centrosome includes a pair of centrioles surrounded by radiating strands of microtubules called the aster. The microtubule by radiating strands of microtubules called the aster. The microtubule organizing centre that forms the mitotic spindle in dividing cells.organizing centre that forms the mitotic spindle in dividing cells.

In Plants there is no CentrioleIn Plants there is no Centriole

They use MTOCs: Microtuble Organizing They use MTOCs: Microtuble Organizing CentersCenters

Plant cells create mitotic spindle fibers and Plant cells create mitotic spindle fibers and have a centrosome they lack centrioles. have a centrosome they lack centrioles.

What are spindle fibers made of?What are spindle fibers made of?

MicrotublesMicrotubles

Microtubles grow from the centrosomes Microtubles grow from the centrosomes Polar Microtubles: Attach to other polar Polar Microtubles: Attach to other polar

microtubles spaning the cell.microtubles spaning the cell. Kinetochore microtubles: attach to the Kinetochore microtubles: attach to the

kinetochore. Breakdown From Here.kinetochore. Breakdown From Here.

Microtubuleformation

and disassembly

A gene is a segment of DNA that codes for a protein or RNA molecule which guide the development of traits.

Cell TypesCell Types

Somatic CellsSomatic Cells

GametesGametes

Chromosome NumbersChromosome Numbers

Types: Autosomes and Sex Types: Autosomes and Sex Chromosomes (XX or XY).Chromosomes (XX or XY).

Humans: 22 pair of Humans: 22 pair of homologous chromosomes homologous chromosomes and 1 pair of sex and 1 pair of sex chromosomes.chromosomes.

Chromosome Numbers

All of the cells in the body, other than gametes are Diploid (2n=46 in humans).

Gametes contain only one set of chromosomes: Haploid (n=23 in humans).

Different species have Different species have different numbers of different numbers of chromosomes.chromosomes.

Change in chromosome number

Humans who are missing even one of the 46 chromosomes usually do not survive.

Humans with more than two copies of a chromosome, result in a condition called trisomy.

Abnormalities in chromosome number can be detected by analyzing a karyotype.

Nondisjunction during the production of gametes results in gametes having more or less chromosomes than normal.

Pictures called karyotypes can detect problems after conception.

How do Prokaryotes divide? How do Prokaryotes divide?

They divide by binary fission. Their DNA is They divide by binary fission. Their DNA is circular and usually only has one strand. circular and usually only has one strand.

No Mitosis!!!No Mitosis!!!

Bacterial cells divide to reproduce

Binary fission is a form of asexual reproduction that produces identical

offspring: Mitosis

The Cell Cycle: for Eukaryotes Fig 12.5,12.4, 12.17

The cell cycle is a repeating sequence of cellular growth and division during the life of an organism.

A cell spends 90 percent of its time in the first three phases of the cycle.

Time to divide& multiply!

I’m working here!

Key checkpoints at which feedback signals from the cell can trigger the next phase of the cell cycle (green light).

Cell Cycle Movie/Game

Overview of the cell cycle

Checkpoint control systemCheckpoint control system3 major checkpoints:3 major checkpoints: G1/S: Called “Restriction Point”

can DNA synthesis begin?can DNA synthesis begin?

G2/M

has DNA synthesis been completed has DNA synthesis been completed correctly?correctly?

commitment to mitosiscommitment to mitosis spindle checkpoint

are all chromosomes attached to are all chromosomes attached to spindle?spindle?

can sister chromatids separate can sister chromatids separate correctly?correctly?

GG11/DNA Synthesis checkpoint/DNA Synthesis checkpoint

GG11/S checkpoint is most critical/S checkpoint is most critical primary decision pointprimary decision point

““restriction point” if cell receives if cell receives “GO” signal, it divides it divides

internal signals: cell growth (size), cell nutrition internal signals: cell growth (size), cell nutrition

external signals: “growth factors”external signals: “growth factors” if cell does if cell does not receive receive

signal, it exits cycle & signal, it exits cycle & switches to switches to G0 phase

non-dividing, working statenon-dividing, working state

GG00 phase phase

MMitosis

G1Gap 1

G0Resting

G2Gap 2

SSynthesis

GG00 phase phase non-dividing, differentiated statenon-dividing, differentiated state most human cells in Gmost human cells in G00 phase phase

liver cells in G0, but can be

“called back” to cell cycle by external cues

nerve & muscle cells highly specialized arrested in G0 & can

never divide

What molecules control cell What molecules control cell division?division?

2 types of molecules control2 types of molecules control Cyclins oscillating levels during cell division.Cyclins oscillating levels during cell division. Cycline dependent kinasis or CDKsCycline dependent kinasis or CDKs

First CDK discovered was MPF/ p-phase First CDK discovered was MPF/ p-phase promotor factor. promotor factor.

When control is lost: cancerFig 12.19, 12.20

Cancer is the uncontrolled growth of cells due to loss of contact inhibition / density-dependent inhibition.

Overcrowding and tumors

Mutations in genes that control cell division may result in cancer.

If Telomerase ends are left on DNA, cells don’t die after 50 or so divisions. (Built in destruction control)

HeLa Cells: Most widely used cancer cell line.Named after a woman 40 years ago with cervical cancerImmortal. Each cell has 70-80 chromosomes instead of 46.

Hit the Cancer BiologyDocumentary Link

Why do cells have to divide?Why do cells have to divide?

They outgrow their nuclear capacity.They outgrow their nuclear capacity. Surface area to volume ratioSurface area to volume ratio MetabolismMetabolism

Some cells are large. How do they Some cells are large. How do they overcome the problem?overcome the problem? MultinucleatedMultinucleated

Human skeletal muscle cellsHuman skeletal muscle cells

Paramecium (2 nuclei)Paramecium (2 nuclei)

Slime Mold Fungus (1000’s of nuclei)Slime Mold Fungus (1000’s of nuclei)

The Phases of Mitosis The Phases of Mitosis pg 232-233pg 232-233(How to make a clone)(How to make a clone)

InterphaseInterphase

ProphaseProphase

MetaphaseMetaphase

AnaphaseAnaphase

TelophaseTelophaseCytokinesis Cytokinesis

II PPrefer refer MMy y AAwesome wesome TTeacher…eacher…CCool!ool!

MITOSIS

The Jazzy Version of

Mitosis

ProphaseProphase1.Chromosomes

coil and become visible.

2.Nuclear envelope & nucleolus breaks down.

3. Mitotic Spindle fibers begin to form.

MITOTIC SPINDLE

CENTRIOLES

CENTROMERE

NUCLEAR ENVELOPE

HOMOLOGUES

MetaphaseMetaphase 1.Chromosomes

line up along the equator of the cell.

2.Spindle fibers attach to kinetochore.

3.Centrioles migrate to the poles of the cell.

AnaphaseAnaphase

1.Spindle fibers begin to shorten.

2.Chromatids separate.

3.Chromatids begin moving toward the poles of the cell.

TelophaseTelophase1.Nuclear envelope reforms.

2.Cleavage furrow forms pinching the cytoplasm.

3.Chromosomes uncoil.

4.Cytokinesis begins.

Cytokinesis Fig 12.9

During telophase, cytokinesis occurs.

During cytokinesis, the cytoplasm of the cell is divided in half, and the cell membrane grows to enclose each cell.

Cleavage In

Action

Actin and Myosin in a ring formation contract causing cleavage.

How does a cell plate form in How does a cell plate form in plants?plants?

In Telophase: Golgi apparatus filled with cell wall materials move by microtubles to the middle of the cell and fuse.

Plants do not separate. Plants do not separate.

Middle Lamella holds cells together. Middle Lamella holds cells together. StickySticky

Meiosis Meiosis Fig.13.7 & 13.8Fig.13.7 & 13.8

USA 300,000,000 strong and growingUSA 300,000,000 strong and growing

Meiosis produces gametes and Meiosis produces gametes and reduces the number in chromosomes reduces the number in chromosomes in half.in half.

The following presents mitosis on the The following presents mitosis on the left and the corresponding meiosis left and the corresponding meiosis phase on the right….notice the phase on the right….notice the differences.differences.

The Theory of Inheritance of GenesThe Theory of Inheritance of Genes

First Link First

A forest from the trees momentA forest from the trees moment

Meiosis 1Meiosis 1 Reduction Division: Process by which Reduction Division: Process by which

homologous chromosomes separate.homologous chromosomes separate. Each Chromosome pairs up precisely with its Each Chromosome pairs up precisely with its

homologue.homologue.

Meiosis 2Meiosis 2 Separation of sister chromatids.Separation of sister chromatids. Similar to Mitosis.Similar to Mitosis.

Prophase Prophase IProphase Prophase IGenetic Recombination: Cross-over

Synaptomeal Complex: Pairing of homologues (Synapsis)

The Longest Phase

Chiasmata (pl) Chiasma (s)Chiasmata (pl) Chiasma (s)GeneticsGenetics The point of contact between The point of contact between paired chromatids during meiosis, paired chromatids during meiosis, resulting in a cross-shaped configuration resulting in a cross-shaped configuration and representing the cytological and representing the cytological manifestation of crossing over. manifestation of crossing over.

Metaphase Metaphase IMetaphase Metaphase I

Chromosomes line up on metaphase plate. (double file)

Spindle fibers attach at kinetochore.

Anaphase Anaphase IAnaphase Anaphase I

Homologous chromosomes separate

Telophase Telophase I Telophase Telophase I

& Cytokinesis & Cytokinesis I & Cytokinesis & Cytokinesis I

Each pole has the monoploid number of chromosomes

May or may not go into interphase.

None Prophase II None Prophase II

None Metaphase IINone Metaphase II

None Anaphase IINone Anaphase II

None Telophase II None Telophase II

& Cytokinesis II& Cytokinesis II

Formation of GametesFormation of Gametes

SpermatogenesisSpermatogenesis

spermatids

OogenesisOogenesis

OVUM

Third LinkComparison ofOOGENESIS

&SPERMATOGENISIS

So How Do Mitosis and Meiosis So How Do Mitosis and Meiosis Compare?Compare?

..

Comparison of Mitosis and Meiosis

Types of ReproductionTypes of Reproduction

Sexual and AsexualSexual and Asexual Sexual: MeiosisSexual: Meiosis Asexual: Binary fissionAsexual: Binary fission

What are the three ways genetic What are the three ways genetic variation is produced?variation is produced?

Independent AssortmentIndependent Assortment Meiosis 1: random separation of homologous Meiosis 1: random separation of homologous

chromosomes. 50% maternal or paternal C (2^23)chromosomes. 50% maternal or paternal C (2^23)

CrossoverCrossover Recombinant chromosomes are producedRecombinant chromosomes are produced Humans: 2-3 crossovers/chromosome pairHumans: 2-3 crossovers/chromosome pair RandomRandom

Random FertilizationRandom Fertilization Human Ovum = 8 million chromosomal combos Human Human Ovum = 8 million chromosomal combos Human

Sperm = 8 million chromosomal combosSperm = 8 million chromosomal combos Fertilization = 8 million X 8 million recombinations Fertilization = 8 million X 8 million recombinations

possible. possible.

Did you know? A man and a woman Can create 64 trillion

different offspring?