CELL DIVISION

Mitosis and MeiosisMitosis and MeiosisASEXUAL

(EUKARYOTES ONLY)

SEXUAL

I CAN: Compare the advantages of sexual reproduction and asexual reproduction in different situations.

DNA is the molecule that transfers hereditary information from one cell to the next.

This is a model of the double helix shape of DNA.

Pg 233

When a cell is dividing, DNA winds up tightly and forms chromosomes in the nucleus of the cell. A Copy of DNA is needed in all cells.

A specific portion of the DNA code is called a gene, which has genetic information.

The genes are contained within the chromosome.

Pg 139

A karyotype is a picture showing the arrangement of a full set of human chromosomes.

Humans have 46 (or 23 pairs) of chromosomes

In animals…

Somatic cells (cells of the body) are diploid. This means that each cell has two chromosomes of each type. They are in PAIRS.

Gamete cells (egg, sperm) are haploid. This means that each cell has only one of each type of chromosome.

Biologists use “2N” to symbolize diploid.

Biologists use “N” to symbolize haploid.

MITOSIS

When somatic (body) cells reproduce themselves the process

is called MITOSIS.

Main purposes of mitosis:1. Growth2. Repair3. Asexual reproduction (bacteria)

Mitosis leads to the production of two “daughter cells”.

Each daughter cell has the same number of chromosomes as the parent cell.

2N

2N

2N

Somatic Cell

Daughter Cells

Pg 141

INTERPHASE - DNA replicates

PROPHASE - chromatin condenses into chromosomes/nuclear membrane breaks down

METAPHASE - chromosomes are lined up in the middle..

ANAPHASE - Sister chromatids separate and migrate to opposite poles.

TELOPHASE - chromosomes decondense

CYTOKINESIS. division of cytoplasm

The steps of Mitosis: PAGE 141

WEEKLY TEST – CELL REPRODUCTION AND

ENERGY• IT’S TIME TO TAKE YOUR

EDUCATION MORE SERIOUSLY…

• FRESH …MEN AND WOMEN!!!

UNDERSTANDINGMEIOSIS

• STEP 1: GET A LINELESS SHEET OF PAPER– ON THE FRONT – GIVE TITLE

MY BODY AND

HOW IT GROWS AND

REPAIRS ITSELF!

–DRAW AND DESCRIBE THE PHASES OF MITOSIS! (PAGE 175)

UNDERSTANDINGMITOSIS VIDEO

• STEP 2: ON THE BACK!!! – NUMBER TO 1- 10– GIVE THE ANSWERS (letter only) to

VIDEO QUESTIONS!!!

The steps of Meiosis I and Meiosis II:

MEIOSISWhen gamete (sperm or egg) cells reproduce themselves the process is called MEIOSIS.

Meiosis reduces chromosome #to half.

N

2N

N

Gamete Cell

N N

During meiosis, a single diploid cell divides and produces FOUR

genetically different haploid cells.

In Meiosis there is one chromosome duplication followed by two cellular

divisions (into four cells) so Meiosis is broken down into Meiosis I and Meiosis II.

1 N egg1 N sperm

Upon fertilization, a “N” sperm meets a “N” egg and a zygote (2N) is formed.

2N zygote

Pg 175 Crossing Over, pg 190

Mitosis

• 1 Cell Division

• Produces Body Cells

• Produces 2 daughter cells

• Daughter Cells are Diploid 2N

• Daughter cells IDENTICAL to parent cells

• 2 Cell Divisions

• Produces Sex Cells

• Produces 4 daughter cells

• Daughter cells are haploid N

• Daughter cells are GENETICALLY different from parent cell due to CROSSING OVER of chromosomes

Meiosis