CELL DIVISION

Cell Division/Reproduction

Why?

Cells divide for many reasons: In order to stay

small Diffusion occurs

at a faster, more efficient rate in smaller cells.

Why would diffusion rate matter in cells?

Remember what materials need to enter and exit the cell.

DNA limits their size DNA can only

control cells up to a certain size.

Repair/replace old or damaged cells.

Growth and Development We start out as one

cell, mitosis allows that 1 cell to turn into billions of cells.

Cell Cycles

No nucleus No membrane bound

organelles (ex. mitochondria, vacuole, chloroplast) A.) Cell division takes

place in 2 steps: 1.) DNA is copied 2.) Cell splits by

binary fission

Prokaryotic Cells

Cell Cycles

Contain a nucleus and organelles. Repeating

sequence of growth and division

Occurs in two cycles for two purposes

Mitosis Occurs in somatic

(ordinary body cells) for growth and repair

Creates 2 identical cells

Meiosis Occurs in germ cells

(ovaries and testes) to make gametes (sex cells).

Creates 4 similar cells.

Eukaryotic Cells

Eukaryotic Cell Cycle

3 Stages Interphase

G1: First growth phase

S: Synthesis phase G2: Second growth

phase Mitosis

nuclear division Prophase Metaphase Anaphase Telophase

Cytokinesis Division of cytoplasm

Centromere

Interphase

This is when the cell is preparing to divide.

The LONGEST phase of the cell cycle

90% of the cell’s life is spent in Interphase.

G1 – first growth phase: The cell doubles in

size and the organelles double

S – synthesis phase: the DNA that makes

up the chromatin is copied (DNA replication) this is the longest phase of interphase.

G2 – second growth phase: Growth and

preparation for mitosis, second check-point.

Interphase (G1, S, G2)

Terms to know: (Start a VOCAB page)

Chromosome Single piece of coiled

DNA Diploid

A cell that contains a set of chromosomes from mom and dad. (46 in Humans)

Replicated Chromosome A single piece of DNA

that has been copied through DNA replication

Sister Chromatids 2 identical strands of

DNA Non-Replicated

Chromosome Single strand of DNA

before it is copied

Spindle Fibers Fibers that are

attached to centrioles to help pull apart chromosomes

Centrioles Organelles that aid in

pulling apart chromosomes

Centromere Structure that holds

the replicated chromosomes together

DNA related terms Structural Terms

Mitosis (PMAT)

Mitosis The nucleus of a cell

is divided into two nuclei with the same number of chromosomes.

Cell Stays diploid Consists of 4 phases

ProphaseMetaphaseAnaphaseTelophase

Mitosis Step1: Prophase

Longest phase of MITOSIS Chromatin coils and

forms chromosomes

Nuclear envelope breaks down

Spindle fibers form and stretch from one end of the cell to the other They attach to the

centrioles They help to pull

the cell apart

Mitosis Step2: Metaphase

Chromosomes line up in the middle of the cell

Mitosis Step3: Anaphase

Centromere of each chromosome splits

Two sister chromatids separate and move to opposite poles

Each chromatid becomes separate (non-replicated) chromosome in each daughter cell.

Mitosis Step4: Telophase

Last stage of Mitosis

Chromosomes at each pole uncoil and become chromatin

Nuclear envelope reforms

Spindle fibers break down

Cytokinesis

NOT part of mitosis

The cytoplasm divides into two cells

Cell membrane reforms

In plant cells the cell wall reforms