Cellular Reproduction - Mitosis

MITOSIS = Cell division

When parent cell forms two identical daughter cells

Momma!

Momma!

Daughters!

Why do cells divide?

Multicellular organisms: 1) Growth  2)

Maintenance/repair of tissues (ex: blood cells)

Unicellular organisms: Asexual reproduction

Replication of DNA – copying the genetic material

Distribution of DNA – dividing the genetic material evenly between two cells

Cytokinesis – dividing the cytoplasm between two cells

Cell division involves:

DNA double helix

proteins

Chromatin

Chromosome

DNA is a double helix

When stretched out, it can be as long as 2 meters

Normally, DNA in the nucleus is called CHROMATIN. It is seen as a thin thread loosely wrapped around proteins like a beaded necklace.

Just before cell division, DNA coils tightly into a chromosome. The chromosome is very compact and can be seen with a light microscope

Replication: Copying the DNA

Occurs before the DNA condenses (S phase of interphase)

The original and its identical copy are called sister chromatids.

Sister chromatids are attached to each other by a centromere.

During mitosis, the sister chromatids will be separated so each cell has the complete DNA information

A chromosome is made up of two identical halves called chromatids.

The Cell Cycle

Time from the formation of a cell until it divides

The Cell Cycle Two major phases:

InterphaseMost cell activities occur

Growth

Making proteins

Performing specialized functions

The Cell Cycle Two major phases:

MitosisCell divisionCycle time varies:

Embryonic cells complete the cycle in hours

Stem cells are in interphase for 20 hours

Nerve cells remain in interphase

G1 phase of interphase – growth, duplication of organelles, making proteins.

S-phase of interphase: DNA replication

G2 phase: duplication of centrosome

Stages of Mitosis

Prophase : centrosomes separate and spindle forms; chromosomes are condensing

ProMetaphase : break down of nuclear envelope; centrosomes arrive at two

opposite poles; spindles attach to chromosomes

Metaphase : chromosomes move to the equator

Anaphase : sister chromatids separate (become daughter chromosomes)

Telophase : spindle disappears; nuclear envelope forms, DNA unfolds

cytokinesis: cytoplasm divides

Two daughter cells are now complete

Cytokinesis

Division of the Cytoplasm

Animal cells: cleavage furrow forms

Cell pinches in towards the center

Cytokinesis

 Plant cells: cell plate forms

New cell walls and membranes form from the cell plate

SUMMARY: What happens to chromosomes prior/during mitosis?

 1) chromosomes replicate

 2) chromosomes coil

 3) chromosomes align

 4) sister chromatids separate

 5) chromosomes uncoil

**interphase

**prophase

**metaphase

**anaphase

**telophase

Animal Prophase

Plant

Animal Metaphase

Animal Anaphase

Animal Telophase

Cancer results from uncontrolled cell division.

A cancerous growth is called a tumor.

The Cell Cycle and Cancer

In Cancer, often one of the checkpoints that regulate mitosis don’t work

Cancer cellsLack differentiation

Have abnormal nuclei

Undergo metastasis

The Cell Cycle and Cancer

Cancer treatment:

•Radiotherapy

•Chemotherapy

•Hormonal therapy

•Consumption of foods rich in vitamins A and C (dark green leafy vegetables, carrots, fruits)

•Avoid salted, pickled or smoked food.

•Consumption of vegetables from the cabbage family.

Cancer prevention:

1. Cellular reproduction is an important process for growth and development as well as repair of tissues in multicellular organisms.

2. The cell cycle is composed of a number of phases where specific events occur (interphase and mitosis are the two major phases).

3. Mitosis is divided into four phases: prophase, metaphase, anaphase and telophase, which is followed by cytokinesis

4. Cancer is caused by uncontrolled cell division

Learning objectives