Mitosis and Cell Division

Chromosomes

• Single molecules of DNA, containing thousands of genes

• Humans have 23 pairs or 46 total

• Normally you can’t tell them apart- called chromatin

Chromosome vs. Replicated

Chromosome

Purpose of Mitosis

• To copy the nucleus so that two new cells may form by cell division

Importance of Mitosis• How we grow from a single cell

(zygote) into approximately 100 trillion cells

Identical DNA

• Despite very different appearances and functions every cell in your body has the exact same DNA- because they all came from one original cell dividing

• Differences are due to very complex mechanisms of gene expression that we are only beginning to understand

Other functions of Mitosis

• Grow new cells or repair tissues•Only some cells are capable of regenerating (i.e. skin cells constantly divide, brain cells do not)

Stages of the Cell Cycle

• Interphase – cell grows and prepares for division

• Mitosis – nucleus divides• Prophase• Metaphase• Anaphase• Telophase

• Cytokinesis- Cell divides (overlaps with mitosis)

Interphase

• G1- cell grows and copies necessary molecules/organelles

• S – chromosomes are copied

• G2- cell grows and prepares to divide

Prophase

• Nucleus starts to disappear

• Chromosomes Condense

Metaphase

• Replicated chromosomes line up

Anaphase

• The chromatids are pulled apart

Telophase

• 2 new nuclei form, each with the full set of chromosomes

Cytokinesis

• The cell splits into 2

Control of Mitosis

• The steps are usually closely regulated by “checkpoints” – which prevent the process from continuing if something is wrong

Density and Anchorage Dependencies

• Cells normally stop dividing when things get crowded

• Cells normally have to be anchored to other cells

When Mitosis Is Not Controlled…

• It leads to cancer

What is Cancer?

• A wide variety of diseases, all of which involve abnormal and uncontrolled cell division

• Cancers can get in the way, use up energy resources and cause many other damaging affects

Cell Abnormalities

• Because cells divide early and often, cancerous cells are much more prone to mutations

• These in turn cause the cancer to obey fewer and fewer body control mechanisms and the cancer gets progressively worse

Benign Tumors vs. Malignant (Cancerous)

Benign

• Tumor obeys anchorage dependence and doesn’t spread

• Although not cancerous can still cause health problems

Malignant

• Tumor stops obeying anchorage dependence and spreads (metastasizes)

• Bad news

Facts about Cancer

• Over 100 types – just about any part of the body can become cancerous (usually parts of the body that undergo mitosis often!)

• Around 8-9 million people in the world die each year of cancer (and its increasing!)

• 30% of cancers could be prevented- mainly by avoiding tobacco and eating a healthy diet

• (according to the World Health Organization*)

Cancer in the US

• 1.5 million new cases and about 570,000 deaths per year

• 2nd leading cause of death (1in 4 deaths)

• Estimated to cost the country $228 billion per year

• From Radiation Therapy Answers

• http://www.rtanswers.org/statistics/aboutcancer.aspx

Cancer Research• As a group pick a type of cancer

• Conduct some basic research• What is the cancer? What might cause it?• How prevalent is it? How fatal is it?• What are the effects? Can it be cured?• What else should we know about the cancer?

• Should be basic – 2-4 minutes. Don’t overload us with text – just a nice overview.

• Know what you are going to say- don’t read to us!

Common Types of Cancer

• Lung

• Breast

• Skin

• Prostate

• Leukemia

• Lymphoma

• Pancreatic

• Thyroid

• Kidney

• Colorectal

• Bladder

• Endometrial (uterine)