Chapter 12-The cell Cycle

C-12 The Cell Cycle

 

1855 Rudolf Virchow- A german doctor

"Omnis cellula e cellula

Cells divide by Mitosis

 

 

Cell Division is for:

Reproduction (Amoeba)

Growth and development (Fertilized egg)

Renewal and repair of tissues (Liver, skin)

 

Some Definitions

Genome- the total number of genes in a basic set of chromosomes.

Examples: Humans_________

Frog__________

Dog___________

Chimpanzee_______

Ducks__________

 

Definitions continued

Somatic cells- body cells. All contain 46 chromosomes (Produced by Mitosis)

Gametes- egg or sperm cells. All contain 23 chromosomes (produced by Meiosis)

Chromosomes=Chromatin= Genes=DNA

 

Mitosis

Mitosis- the division of the nucleus and its contents (DNA, nucleolus)

Cytokinesis-the division of the cytoplasm

Mitosis and cytokinesis are just one part of the Cell Cycle

 

Cell Cycle
(Four Parts)

G1 phase- a growth phase

S phase- this is where the DNA (chromosomes) are duplicated)

G2 phase- the cell continues to grow

M phase- this is when mitosis and cytokinesis occur.

 

Mitosis
(Five Parts)

Prophase

Prometaphase

Metaphase

Anaphase

Telophase

 

Cleavage of Animal and Plant Cells

Fig 12.8

Animal Cells- Cleavage furrow

Plant Cells- Cell plate

 

Bacteria Reproduce by Binary Fission

Binary Fission-The type of cell division by which prokaryotes (Bacteria) reproduce. Each dividing daughter cell receives a copy of the single parental chromosome.

Fig 12.10

 

Mitotic Controls

The cell cycle is controlled by:

Internal Signals-Proteins and enzymes- which act as chemical messengers to tell the cell cycle to stop or proceed (Fig 12.13)

External Signals- nutrients, growth factors, cell density and cell attachment.

 

                                                               Cancer

In cancer the cell cycle and all of its control mechanisms become defective and abnormal

Remember- genes control cell division turning it on and off in a controlled fashion.

In cancer cell division stays in the "ON" position. (Fig 12.16)

 

Causes of Cancer

Normal cell>>>>>>> Cancer cell

External carcinogens- chemicals, radiation, viruses- which damage the genes (DNA) that control cell division

Internal mutations- accidental damage during mitosis to the genes (DNA) that control cell division.

Types of Tumors

1.Benign: Usually Harmless

Cells Remain at their original site

Cells are fairly normal looking

Can still cause trouble

 

2.Malignant: Harmful

Metastasize

Cells are not normal looking

Exhibit excessive growth

Abnormal functions and # of chromosomes

 

                                                      Some External Causes of Cancer

Chemicals- smoking, (even secondary smoke) diet

Radiation- UV from sun, nuclear radiation from the atom-alpha, beta and gamma radiation.

Viruses- certain forms of leukemia and cancers of the cervix and liver.

 

Can Cancer be Prevented?

Some- Such as lung cancer which is caused by smoking and is responsible for 164,200 of the 563,000 cancer deaths per year

About 28% of all cancer deaths are caused by just one external factor--Cigarettes

Also causes cancers of: mouth, pharynx, larynx, esophagus, pancreas, uterus, cervix, kidney and bladder.

 

What major chemicals do cigarettes emit?

Benzene

Carbon monoxide

Formaldehyde

Ammonia

Hydrogen cyanide

Others- Nickel, zinc, acetone, formic acid

 

Five Reasons Why You Should Stop Smoking

Live longer

Look younger

Avoid cancer

Save money

Raise healthy kids

 

Can Cancer be Prevented?

ETS- environmental tobacco smoke (secondhand smoke) contains over 4000 chemical compounds

Each year about 3000 nonsmoking adults die of lung cancer as a result of breathing the smoke of others’ cigarettes

ETS-35,000-40,000 deaths from heart disease

ETS-150,000-300,000 respiratory infections

 

Cancer in Woman

22% of woman and 26% of men smoke

20% of female high school seniors smoke

68,000 woman in the U.S. will die of lung cancer this year. (That is-of all the different kinds cancers woman can get, 25% will be from lung cancer.

 

R.J. Reynolds

A recent new ad by this company says:

" Until I find a real man, I’ll take a real smoke"

 

Additional Problems Faced by Woman Smokers

Menstrual irregularities

Infertility

Osteoporosis, Arthritis

Blood clots

Low birth weights, stillbirths, miscarriages and SIDS.

 

Can Cancer be Prevented?

Dietary factors-about 30% of all cancer deaths

Eat more fruits and vegetables

Reduce your intake of fat and cholesterol.

Exercise more to burn calories and strengthen your heart and lungs.

 

Everything Doesn’t Cause Cancer

Relatively few chemicals cause cancer. Most chemicals, even the most toxic or dangerous ones, are not carcinogenic.

 

Test Animals

To determine if a chemical is carcinogenic we test it on animals (mice) in high dosages

We use high dosages to make the cancer appear quicker. A lower dose would take to long.

Noncarcinogens do not produce tumors no matter how how the dose

 

Some Simple Statistical Calculations

If it is determined that a particular chemical is carcinogenic and I told you that this carcinogen can cause cancer in 1 of every 10,000 people exposed to it would this be cause for concern ?

 

Warning signs of Cancer
(CAUTION))

C- change in bowl habits

A- a sore that does not heal

U- unusual bleeding or discharge

T- thickening or lump in the breast or elsewhere

I- indigestion or difficulty in breathing

O- obvious change in a wart or mole

N- nagging cough or hoarseness

Weakness

Fatigue

Weight loss

 

Cancer Treatments

Surgery

Radiation

Chemotherapy

Cancer vaccines

Monoclonal antibodies

Designer drugs

Angiogenesis inhibitors

Oncolytic Viruses

Chemo-prevention