ChromosomesChromosomesand and CellCell

ReproductionReproduction

The Cell Cycle

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.

CELL GROWTH

DNA SYNTHESIS

GROWTH & PREP. FOR MITOSIS

M PASE

G0 PHASE

A cell will enter the last two phases of the cell cycle only if it is about to divide.

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

Bacterial cells divide to reproduce

Binary fission is a form of asexual reproduction that produces identical

offspring: Mitosis

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

How ChromosomesCoil

Each half of a chromosome is Each half of a chromosome is an exact copy called a an exact copy called a chromatidchromatid..

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

A gene is a segment of DNA that codes for a protein or RNA molecule.

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.

Karyotypes Explained

When control is lost: cancer

Cancer is the uncontrolled growth of cells.

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

Cancer Biology

All the Details

The Phases of MitosisThe Phases of MitosisInterphaseInterphase

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

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

MeiosisMeiosisUSA 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.

First Link First

Prophase Prophase IProphase Prophase IGENTEIC RECOMBINATION

INDEPENDENT ASSORTMENT

SYNAPSIS

Metaphase Metaphase IMetaphase Metaphase I

Anaphase Anaphase IAnaphase Anaphase I

Telophase Telophase I Telophase Telophase I

& Cytokinesis & Cytokinesis I & Cytokinesis & Cytokinesis I

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