CELL DIVISION
Mitosis and Meiosis
ASEXUAL
SEXUAL
(EUKARYOTES
ONLY)
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.
Pg 139
The genes are contained
within the chromosome.
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.
Biologists use “2N” to symbolize diploid.
Gamete cells (egg, sperm) are haploid. This
means that each cell has only one of each type
of chromosome.
Biologists use “N” to symbolize haploid.
MITOSIS
When somatic (body) cells
reproduce themselves the process
is called MITOSIS.
Main purposes of mitosis:
1. Growth
2. Repair
3. 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.
Pg 141
Somatic Cell
2N
2N
2N
Daughter Cells
The steps of Mitosis: PAGE 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
WEEKLY TEST –
CELL REPRODUCTION AND
ENERGY
• IT’S TIME TO TAKE YOUR
EDUCATION MORE SERIOUSLY…
• FRESH …MEN AND WOMEN!!!
UNDERSTANDING
MEIOSIS
• STEP 1: GET A LINELESS SHEET OF
PAPER
– ON THE FRONT – GIVE TITLE
MY BODY AND
GROWS AND
REPAIRS ITSELF!
HOW IT
–DRAW AND DESCRIBE THE PHASES OF
MITOSIS! (PAGE 175)
UNDERSTANDING
MITOSIS 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:
Pg 175
MEIOSIS
Crossing Over, pg 190
When gamete (sperm or egg) cells reproduce
themselves the process is called MEIOSIS.
Meiosis reduces chromosome #to half.
Gamete Cell
2N
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.
Upon fertilization, a
“N” sperm meets a “N”
egg and a zygote (2N)
is formed.
1 N egg
1 N sperm
N
N
N
N
2N zygote
Mitosis
•
•
•
•
1 Cell Division
Produces Body Cells
Produces 2 daughter cells
Daughter Cells are
Diploid 2N
• Daughter cells
IDENTICAL to parent
cells
Meiosis
•
•
•
•
•
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