CELL GROWTH AND DIVISION

Unit 3: Chapter 10

Mr. DiBiasio

Question?

When a living thing grows, what happens to its cell? Does an animal get larger

because each cell increases in size or because it produces more cells?

All Living Things Grow and Develop …

Growth means an increase in cell number, not size.

Limits to Cell Growth

There are two main reasons why cells divide rather than continuing to grow:

1) the larger a cell becomes, the more demands the cell places on it DNA2) the cell has more trouble moving enough nutrients and wastes across the cell membrane

DNA Overload

• DNA is what controls a cell’s function and is located in the nucleus

• When a cell gets larger it does not make extra copies of DNA

• This puts extra pressure on the DNA and causes it not to function properly

Cell Division

• To stop the cells from becoming too large, a growing cell divides forming two “daughter cells”. This process is what is known as Cell Division

• Before Cell Division occurs, the cell replicates, or copies, all of its DNA.

• Each Daughter Cell will get its own complete set of genetic information

Reproduction

• Parents produce a new generation of cells or multi-celled individuals like themselves

• Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation

Chromosomes

1. In Eukaryotic cells, chromosomes carry the genetic information that is passed on from one generation of cells to the next.

2. Chromosomes are made up of DNA, which carries the cells coded genetic information- and proteins.

3. The cells of every organism have a specific number of chromosomes.

Chromosomes

7. Because of this, each chromosome consists of two identical, “sister” chromatids.

Human Chromosome Number Diploid chromosome number (n) = 46

Two sets of 23 chromosomes eachOne set from fatherOne set from mother

Mitosis produces cells with 46 chromosomes--two of each type

Cell Division

Mitosis

Division of the nucleus

Cytokinesis

Division of the cytoplasm

Process of Mitosis

MitosisCell reproduction in which two

genetically identical cells are made from one cell.

Which Cells undergo Mitosis?

Body CellsCells that make up the body

Examples: skin, hair, blood, bones, nerves, muscle, etc.

Cell Cycle

Interphase

Usually longest part of the cycle

Divided into 3 phases (G1, S, G2)

Cell increases in mass

DNA is duplicated

Mitosis

Period of nuclear division Usually followed by cytoplasmic division Four stages:

Prophase

Metaphase

Anaphase

Telophase

Prophase Centrosomes move

toward opposite poles.

Spindle fibers form. Nuclear envelope

breaks down. Chromatids are

attached at the centromere.

Nucleolus disappears.

PROPHASE

Metaphase

Chromosomes line up across the center of the cell.

Spindle fibers attach to each chromosomes at their centromere

METAPHASE

Anaphase

Centromeres split.

Sister Chromatids move toward opposite poles.

ANAPHASE

Telophase

Chromosomes disperse. Spindles break apart. Nuclear envelope re-forms

around each group of chromosomes.

Nucleolus becomes visible in each daughter nucleus.

Mitosis Ends

TELOPHASE

Cytokinesis Division of the cytoplasm Usually occurs with Telophase

In animal cells, the cytoplasm is pinched inward, forming a cleavage furrow.

Plant cells form a cell plate, which forms from the inside out.

Uncontrolled Cell Growth

What happens to cells that do not respond to signals that regulate growth?

Cancer a disorder in which some of the body’s own

cells lose the ability to control growth.A disease of the cell cycle

Cancer Cancer cells don’t respond to signals that

regulate growth They divide excessively and form masses of

cells called tumors They can break loose and spread throughout

the body.

Cancer One in three people will develop cancer.

One in four people will die of cancer.

More than 1500 Americans died each day of cancer this year.

Over 1,000,000 cases of skin cancer will be diagnosed this year.

Cancer is the leading cause of death among Americans under the age of 85.

What causes cancer cells?

Cells are transformedBy chemicals, certain viruses, and X-rays

If these cells are not destroyed, they divide and form a mass of abnormal cells called a tumor

Progression of Cancer

NORMAL CELLS

BENIGN

fast dividing cells, not really toxic, only cause mechanical damage

MALIGNANT

toxic, cause local toxicity and inflammation

METASTATIC

travel from one place to another. The real killer

Treatments Surgery – remove the affected cells Radiation – high-dose X-rays kill cells Chemotherapy – drugs kill cells Hormone therapy – hormones stop cell

growth

What causes cancer cells? Cells are transformed What can cause cells to be transformed? (carcinogens)

Chemicals○ Tobacco, pesticides

X-rays (radiation)UV lightFamily HistoryViruses

○ HPV (human papillomavirus), increases risk of cervical cancer.