Telomeres

Each chromosome has an “end cap” called a telomere (“telo” = end, “meros” = part)

Without telomeres,

chromosomes

stick to each other and

“misbehave”

in other ways.

So, telomeres are

important.

When linear DNA gets copied, the enzymes can’t quite get the last section. That means that every DNA replication results in just a little less DNA.

Telomeres are “expendable” in terms of information, because they seem to be repeating nucleotides that don’t code for anything important.

BUT… eventually you run out of telomeres and start getting into actual DNA.

• In many cells (particularly embryonic cells and unicellular organisms) an enzyme called telomerase will add telomere nucleotides to the DNA sequences.

• Normal human somatic cells lose their telomeres as we age.

• However, telomerase is often at work in cancer cells, allowing them to continue to divide without dying.

CancerCancerNormal Cells

• Cell cycle is regulated (spend a lot of time in interphase)

• Die when “old”• Contact inhibition• Anchorage

dependency

Cancer Cells• Unregulated cell

cycle (short interphase)

• Some never “die”• Grow even when

crowded• Don’t need

something to grow on

• 200+ types

Some terms:

• Oncology = Study of Cancer

• Tumors:

Benign = do not spread to other tissues

Malignant = spread to other tissues

(metastasis)

Causes

1. More than 80% of cancers are “caused”

by factors that can be controlled:

a) Chemicals, such as tobacco

b) High fat, low fiber diets , alcohol

c) Obesity

d) Radiation, like UV rays and X-rays

e) Viruses, like HPV

2. Heredity causes a predisposition to certain cancers. Ex: BRCA1 gene

“Predisposition” means you are more likey to get that kind of cancer, but having the gene doesn’t mean you will definitely get it.

Most Common Types of Cancer

1. Skin Cancer – 98% survival rate

Symptoms of Skin CancerA small lump (spot or mole) that is shiny, waxy, pale in color, and smooth in texture.A red lump (spot or mole) that is firmA sore or spot that bleeds or become crusty. Also look for sores that don't heal.Asymmetrical growths or spots, jagged edges.Flat scaly areas of the skin that are red or brown. Spots or lumps that are various colors.

Some pictures of skin cancerBasal Cell Carcinoma

Malignant Melanoma

Squamous

Cell

Carcinoma

2. Lung Cancer – only 13%

survival rate

9 out of 10 due to smoking

Second-hand smoke a risk

factor

Most common cancer to die from

3. Breast Cancer – survival rate up to 85%

0.5% of patients are men!

Heredity / high fat diet increase risk

4. Colon Cancer – survival rate 61%Second-highest cause of cancer deathsHeredity, high fat/low fiber diet increaserisk

5. Pancreas – survival rate only 4%Smoking/high fat diet increase riskDeath within 6 months of diagnosis

6. “Leukemia” is a term that refers to a type of cancer that affects blood cells. With leukemia, there is no tumor, just an overproduction of blood cells (that aren’t working properly)

Screening for Cancer

Screening for cancer has increased survival rates because the sooner treatment starts, the better chance you have …. Hopefully you catch cancer before it spreads (metastasizes)

Examples: Self screens for skin, breast cancer

PAP smears for cervical cancerPSA test for prostate cancer

Colonoscopy for colon cancer

Treatment

1. Surgery2. Chemotherapy – chemicals that kill

rapidly dividing cells3. Radiation – usually X-rays, that kill cells4. Bone Marrow Transplants (Leukemia) 5. Many others – each type demands a specific therapy. No one treatment “fits all”