Meiosis

Why Do cells Go through Meiosis?Cells go through

Meiosis in order to make Sex Cells

Sex cells are also called Gametes

Four Daughter Cells are created

Haploid (1N)

Interphase

Cell GrowsDuplicates DNACell Prepares to divide

After InterphaseIn order to make sex cells or cells with half

the number of chromosomes meiosis has TWO phases

Meiosis I and Meiosis II

Prophase IChromosomes

Condense (visible)Homologous

chromosomes form a tetrad

Crossing Over Occurs

Crossing OverHomologous

Chromosomes- Similar Chromosomes, Same genes in the same location

When the chromosomes touch they switch genes

Causes genetic variation

Metaphase I Homologous

chromosomes move together to the middle of the cell

Spindle attaches to the centromere

Anaphase IHomologous

chromosomes separate

Sister chromatids stay attached

Move towards opposite poles

Telophase IDivision of

cytoplasmCreates Two

daughter cellsBegin Meiosis IIThere is no

interphase IIWhy?

Prophase IISpindles re-appearNuclear membrane

stays separated

Metaphase IIChromosomes line

up in the middleSpindle attaches

How are metaphase I and II different?

Anaphase IISister Chromatids

Separate from each other

How are Anaphase I and II different from each other?

Telophase IINucleus reformsDivision into four

daughter cellsHaploid (1N)Gametes (egg and

sperm)

Mitosis & the Cell Cycle

Cell Growth & Development

Are cells of organisms the same size? Do your cells get bigger as you grow, or do you just produce more cells?

When talking about Cell Size…… Smaller is Better!

The larger a cell becomes, the more demands the cell places on its DNA, and the harder it is to supply with nutrients.

Cell Division Before a cell becomes to large, a

growing cell will divide. Cell division is the process by which

a Single cell divides into 2 Daughter cells.

Cell Division = the series of events that cells go through as they grow and divide.

Chromosomes Chromosomes=

are composed of DNA-Which carries the cell’s coded genetic information.

Humans have 46 chromosomes(23 pairs).

The chromosomes consist of two identical sister chromatids.

Two Major Types of Cell Division

Mitosis- Somatic cells (Body Cells) Diploid 2N

Meiosis- Sex cells/ Gametes Haploid 1N

Mitosis Mitosis is the process by which the

genetic information is replicated and distributed to daughter cells.

2 diploid(2N) daughter cells are produced from 1 diploid (2N) parent cell.

The Daughter cells are genetically identical to the parent cells.

There are 4 major stages to mitosis, Not including interphase.

Interphase Interphase= The cell spends most of

its life here; not part of the actual reproduction. NOT PART OF MITOSIS. Cell grows and replicates its DNA and

centriole Nuclear membrane is visible Nucleus, Nucleoli, and chromatin can

be seen.

Interphase

Prophase Prophase: first

phase of Mitosis Nuclear membrane

breaks down Chromosomes

become visible Centrioles

separate Spindle forms

Metaphase Metaphase:

Second part of Mitosis Chromosomes

attach to spindle Chromosomes line

up across the MIDDLE of the cell

Anaphase Anaphase: Third

step in Mitosis The sister

chromatids separate and move apart towards opposite poles

Telophase Telophase: Fourth

stage of Mitosis Chromosomes

gather at opposite ends of the cell

The nuclear membrane begins to form and enclose the chromosomes

Cell membrane begins to move inwards

Cytokinesis Cytokinesis: Final

stage in cellular division

Not Mitosis Works with

telophase The cytoplasm

divides completely in half.

2 daughter cells with identical genetic information are produced.