DNA STRUCTURE, DNA REPLICATION, MITOSIS &

CANCER

CP Biology

DNA Holds the genetic information. DNA is inside every cell except for mature

Red Blood Cells (RBCs). In humans, DNA is divided up into 46

pieces called chromosomes. Chromosomes are paired(23). Chromosomes are made up of thousands

of genes. Genes are various sequences of DNA

bases.

DNA SHAPE: DOUBLE HELIX – SPIRAL STAIRCASE

WATSON, CRICK & WILKINS Discovered the

structure of DNA in 1953.

Won the Nobel Prize for this discovery in 1962.

FYI: Rosalind Franklin was responsible for much of the research and discovery work that led to the understanding of the structure of DNA. She died at the age of 37, four years before the Nobel Prize was given. Many believe her name should also be included in discovering the structure of DNA since her X-ray diffraction image was paramount for Watson & Crick.

http://www.youtube.com/watch?v=sf0YXnAFBs8

“Steps” of the ladder are made up of four bases also held together by hydrogen bonds.

Sides of “ladder” are made up of alternating sugars and phosphates held together by a hydrogen bond.

S

S

S

S

P

P

P

PS

A - T

G - C

CHARGAFF’S RULE: ONE PYRIMIDINE AND ONE PURINE MATCH UP TO MAKE ONE STEP OF THE DNA LADDER.

Adenine always pairs with Thymine.

Guanine always pairs with Cytosine.

Bases only attach to:

another base

sugar

Phosphates only attach to sugars

SECRET OF LIFE: PART 1:

http://www.youtube.com/watch?v=unBlYYxMWjE&feature=related

10 min.

DO NOW!1. What structure holds genetic information?2. What are the 4 bases?3. What does phosphate attach on the DNA

strand?4. What sugar is found in DNA?5. How many rings do purines have? ____

Pyrimidines?___6. Name the 2 purines and pyrimidines,

respecitively.

7. To what two structures does sugar connect to in the DNA strand?

Our DNA is split up into 46 chromosomes. Before a cell can divide, the DNA must

first replicate. (46 92) In that way, we keep the same amount of

DNA in our cells after they divide into two cells.

Our cells go through DNA replication right before they go through cell replication.

CHROMOSOME STRUCTURE

COPYING THE CODE

Each strand (of the double helix) has all the information needed to reconstruct the other half by the mechanism of base pairing.

Because each strand can be used to make the other strand, the strands are said to be complementary.

STEP 1: DNA REPLICATION

A section of DNA unwinds and opens into a replication fork.

STEP 2: DNA REPLICATION New nucleotides are added according

to the base pairing rule (Chargaff’s Rule) forming a new complimentary strand.

STEP 3: DNA REPLICATION

DNA Polymerase proofreads the new strand for mistakes and if a mistake is found, it can go back, remove the mistake, insert the correction, and continue on.

After proofreading, there may be only one mistake every 1 billion nucleotides

During replication, DNA may be lost from the tips of chromosomes, which are called telomeres.

When the telomeres are all used up, a normal cell will self-destruct thus preventing loss of any valuable DNA from the exposed tips which could lead to a mutation.

REPLICATION IN EUKARYOTIC CELLS

Eukaryotic cells have much more DNA (all contained in chromosomes, which are in the nucleus)

Replication begins at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.

REPLICATION IN PROKARYOTIC CELLS

Most prokaryotes have a single, circular DNA molecule in the cytoplasm.

Replication in most prokaryotic cells starts from a single point and proceeds in two directions until the entire chromosome is copied.

DNA REPLICATION

http://youtube.com/watch?v=Luw5_z8mIrI&feature=related

http://youtube.com/watch?v=teV62zrm2P0&feature=related

Now that the DNA has replicated, the cell is ready to divide.

This step is called mitosis.•www.synapses.co.uk/genetics/dnastruc.html

•

ASEXUAL VS. SEXUAL REPRODUCTION

Asexual Reprod.: no mix of DNA; all offspring are clones of the original.

Sexual Reprod.: genetic variation; DNA from two individuals are mixed together.

Sexual Reprod. Is an evolutionary advancement over asexual reproduction.

Binary Fission

Ex. bacteria

THE CELL CYCLE• Interphase (G1, S, G2)

• Mitosis (prophase, metaphase, anaphase, telophase)

• Cytokinesis

cytokinesis

INTERPHASE

Most cells spend a majority of their life in Interphase.

In G1 stage: cell growth. S stage: DNA replication occurs.

The G2: all other organelles replicate.

Interphase

*G0 phase is the phase where the cell is just hanging out. Its not growing; it is an active cell undergoing regular cell processes.

WHAT IS MITOSIS?

Definition:Mitosis is nuclear division plus cytoplasmic division, that produces two identical daughter cells.

MITOSIS IS DIVIDED INTO 4 PHASES:

PROPHASEPROPHASE

Plant cell

Animal cell

Animal cell

METAPHASMETAPHASEE

ANAPHASEANAPHASE

The paired chromosomes separate at the centromeres and move to opposite poles.

ANAPHASEANAPHASECONTINUEDCONTINUED

Late Telophase in Animal Cells:

-a cleavage furrow begins to form pinching the one cell eventually into two cells.

Cleavage furrow

LATE TELOPHASE IN PLANTSLATE TELOPHASE IN PLANTS:: --A A CELL PLATE CELL PLATE BEGINS TO FORM, BEGINS TO FORM, EVENTUALLY DIVIDING THE CELLS INTO TWO EVENTUALLY DIVIDING THE CELLS INTO TWO CELLS.CELLS.

Telophase marks the end of mitosis.

The next phase is Cytokinesis: the division of the cytoplasm.

The two phases usually run together.

CYTOKINESIS

HOW LONG DOES THIS ALL TAKE?

Time length varies depending on the type of cell.

A TYPICAL ANIMAL MITOSIS SLIDEA TYPICAL ANIMAL MITOSIS SLIDE

TYPICAL PLANT CELL

CAN YOU FIND ALL THE PHASES IN THE CAN YOU FIND ALL THE PHASES IN THE PLANT MITOSIS SLIDE?PLANT MITOSIS SLIDE?

Can you find all the phases in the plant mitosis slide?Can you find all the phases in the plant mitosis slide?

DO NOW! NAME THAT PHASE

1. 5.

2. 6.

3. 7. 4.

8. What do plant cells create during telophase that animal cells do not?

9. What do animal cells create during telophase that plant cells do not?

10. What mitotic structure is found in animals but not in plants?

WHY DIVIDE? As a cell becomes larger, its volume

increases faster than its surface area. When a cell is too big there are more

demands on the DNA: Obtaining enough oxygen Obtaining nutrients Getting rid of waste

A cell may die due to starvation or poisoning.

MITOSIS ON YOUTUBE

http://www.youtube.com/watch?v=VlN7K1-9QB0&NR=1

Mitosis gone wild

WHAT IS CANCER?WHAT IS CANCER?

What we think of as "cancer" is actually a group of more than one hundred separate diseases.

These diseases are all characterized by an abnormal and unregulated growth of cells, in essence, mitosis ‘gone wild”

This growth destroys surrounding body tissues and may spread to other parts of the body in a process that is known as metastasis.

You cannot catch cancer from someone else.

CANCER IS….

Unregulated cell growthCells no longer respond to normal control mechanisms

They no longer heed to normal signals that regulate cell cycle

They do not stop dividing when growth factors are depleted.

FYI: Cancer affects only multi-cellular organisms

CHECKPOINTS (P53)CHECKPOINTS (P53)

All cells have checkpoint controls where certain genes/proteins, such as p53 , help cells decide whether they should:

1. repair damaged DNA (when this occurs, cells are said to be in CELL-CYCLE ARREST) or

2. commit cellular death (apoptosis).

CHECKPOINTS (P53) CONTINUEDCHECKPOINTS (P53) CONTINUED

Mutation is a sudden change in the base pair sequence of DNA.

Mutations to p53 result in damaged DNA being allowed to proceed through mitosis, passing on even more mutations.

Half of all cancers involve mutations to p53

NORMAL CHECKPOINT SITES

1. WHICH DIAGRAM SHOWS CANCER CELLS? HOW DO YOU KNOW?

2. Compare and Contrast Explain how cancer cells are different from normal cells. Then, relate these characteristics to the diagram above that shows cancer cells.

3. Predict Look at the cancer cells shown above. What can happen if these cells are left untreated?

4. Apply Concepts Explain the role that p53 might have had in the growth and division of the cells shown in each diagram above.

5. Problem Solving How might the cancer cells shown in the illustration above be prevented from doing more harm to the organism they are a part of?

CANCERCANCER:: When a cell repeatedly divides, a

mass called a tumor forms. Tumors put pressure on surrounding

cells and interfere with their function. Cancer cells may also break off of a

tumor and spread throughout the body in a process called metastasis.

When these proto-oncogenes mutate and become When these proto-oncogenes mutate and become oncogenesoncogenes, , they become capable of causing cancer.they become capable of causing cancer.

Melanoma: Dear 16 year old me:

http://www.youtube.com/watch?v=_4jgUcxMezM

TUMORS

The tumor is fed by anThe tumor is fed by an independent blood supply to the tumor.

TUMORS CAN CAUSE TUMORS CAN CAUSE DESTRUCTION IN FOUR COMMON DESTRUCTION IN FOUR COMMON

WAYS:WAYS:1. Tumors put 1. Tumors put pressurepressure on nearby tissues on nearby tissues

and/or organs. and/or organs. 2.2. Tumors Tumors invade tissues and organsinvade tissues and organs directly directly

(direct extension), often damaging or (direct extension), often damaging or disabling them in the process.disabling them in the process.

3. 3. Tumors make invaded tissues and/or organs susceptible to infection.

4. Tumors can also 4. Tumors can also release substancesrelease substances that that destroy tissues in close proximity to them.destroy tissues in close proximity to them.

LUNG TUMOR HAS INVADED THE SOFT TISSUE SURROUNDING IT AND HAS PUT PRESSURE ON OTHER ORGANS.

TUMORS CAN BE EITHER MALIGNANT OR BENIGN.

A malignant tumor is cancer, and a benign tumor is not. Benign tumor will not spread (metastasize). Benign tumor grow by enlarging rather than invading. Ex. Fat tumors A malignant tumor will eventually metastasize and

invade all parts of the body (if left untreated). Don’t look at following picture if you’re squeamish.

Cancer cells metastasize throughout the body via the vascular system.

Cancer can develop anywhere in the body, and at any age.

CARCINOGEN

Is a cancer-causing agent

WHAT ARE THE CAUSES AND RISK FACTORS FOR CANCER?

1. Tobaccosmoking causes 30% of all cancer deaths in the U.S. and is responsible for 87% of cases of lung cancer.

Quitting smoking immediately decreases your risk factor for cancer.

Girls who smoke 10 cigarettes per day or more are at greatest risk, particularly for abdominal obesity.

What are the Causes & Risk Factors for What are the Causes & Risk Factors for Cancer?Cancer?

2. Environmental Factors2. Environmental Factors

RadiationRadiation•Solar UV radiationSolar UV radiation •X-raysX-rays•power linespower lines •cell phonescell phones

3. Air Pollution

4. Water Pollutants• Carcinogens such as chlorine by-products, industrial chemicals, heavy metals, pesticide residues, fluoride, arsenic, hormone-disrupting chemicals, coal-fired power wastes.

Pharmaceuticals Found in Drinking WaterAOL ^ | 3/9/08 | AP Staff Posted on Sunday, March 09, 2008 7:13:43 PMPharmaceuticals — including antibiotics, anti-convulsants, mood stabilizers and sex hormones — have been found in the drinking water supplies measured in quantities of parts per billion or trillion, far below the

levels of a medical dose.

5. Toxic Products

•Plastics: • Never freeze liquids in plastic then thaw

out to drink/eat. • Never microwave food in plastic

containers. Plastic chemicals (dioxins) will leech into the food/drink.

• Dioxins can cause cancer.Read about Personal Health: http://chicagoconservationcorps.org/blog/wp-content/uploads2/2008/08/L05%20Green%20Guide%20Print_%20Plastic%20Containers.pdf

6. Natural Carcinogens

Mold growth in damp areas like basements.Radon gas leaking into buildings

7. Unsafe Sex Practicing unsafe sex can increase your risk of developing a

virus called HPV (human papillioma virus.) HPV increases your risk factor for cervical, anal, vulvar and

vaginal cancer. HPV is so common that at least 50% of sexually active men and

women get it at some point in their lives.

FYI: there is now a controversial vaccine available to prevent getting HPV.

FYI: CERVARIX AND GARDASIL. Gardasil is also licensed, safe, and effective for

males ages 9 through 26 years for girls who are 11 or older .

Several types of cancer are associated with HPV:

Cervical cancer: The most common HPV-associated cancer. Almost all cervical cancer is caused by HPV.

Vulvar cancer: About 40% are linked to HPV. Vaginal cancer: About 70% are linked to HPV. Penile cancer: About 40% are linked to HPV. Anal cancer: About 85% are linked to HPV. Cancers of the head and neck are mostly caused by

tobacco and alcohol, but recent studies show that about 25% of mouth and 35% of throat cancers may be linked to HPV.

8. Lifestyle and Diet Factors

Diet–too much meat, not enough fruits and vegetables.

Obesity, and lack of regular exercise.

9. Other Food Factors1. Processed food such as nitrosamines, aspartame, some food colorants.•2. Bovine growth hormone in milk. (this hormone makes the beef muscle bigger and then it is secreted in the cows milk)

•3. Some salt-cured, pickled, and smoked food.

4. Alcohol consumption.

5. Food contaminated with pesticides and herbicides (not grown organically.)

RBGH in your milk: http://vimeo.com/1221481

10. Other Factors:

Exposure to toxic substances pre-conceptually, in utero, during infancy, during puberty.Family history of cancer–shared habits, shared pollution, shared genes.Poverty.Living near toxic sources.Genetic variability–some people are more vulnerable than others. (Braca 1)

TREATMENTS

1. Chemotherapy: kills all fast replicating cells

2. Radiation: locally kills cells3. Surgery: removes cells/tumor4. Stem cell: research may lead to cancer cures because stem cells can be turned into any kind of cells. (Section 10.4: Stem Cells)

5. News in cancer treatment: Personalized medicine?

http://www.cbsnews.com/video/watch/?id=4580875n

TUMOR PHOTOS

WARNING:

Not for the squeamish.Neurofibromitosis

Breast cancer

Facial tumors

Skin cancer

Tongue cancer

Lip cancer

NEUROFIBROMITOSIS: benign

Breast Cancer: malignant

Facial Tumors: benign

Skin cancer: malignant

Tongue cancer: malignant

LIP CANCER: FROM SMOKING

Most cancer is preventable. Take the time and effort to take care of

yourself. Stay away from harmful environments,

activities, and foods that are known to be carcinogens.

Check yourself. Don’t be embarrassed to seek help. Don’t ignore a noticeable change in

your body. Early detection could save your life.

Testicular cancer is the most common cancer in American males between the ages of 15 and 34 ( 1 in 270 people will get it)

Over the course of a lifetime, 1 in 8 women will be diagnosed with breast cancer.

FYI

Answers to some questions that I have been asked during this chapter.

ASEXUAL REPRODUCTION

Some organisms reproduce without the use of sex cells or a partner.

BUDDING

Ex. Sponges,Yeast & Hydra

VEGETATIVE PROPAGATION

REGENERATION

Ex. Sea Star

SPORES

Fungi and some algae can also utilize true asexual spore formation, which involves mitosis giving rise to reproductive cells called mitospores that develop into a new organism after dispersal. This method of reproduction is found for example in conidial fungi and the red alga

PARTHENOGENESIS

is an asexual form of reproduction found in females where growth and development of an embryo or seed occurs without fertilization by males. The offspring produced by parthenogenesis are always female in species where the XY chromosome system determines gender.

HOW ARE TWINS CREATED? Fraternal twins – 2 eggs fertilized by two sperm. Identical Twins – 1 egg fertilized by 1 sperm. The embryo splits

with the first few days creating 2 identical people sharing 1 placenta.

WHAT’S A HERMAPHRODITE?

Hermaphrodites are divided into two main categories: 1. Organisms that possess both active male and active Organisms that possess both active male and active

female reproductive organs at the same timefemale reproductive organs at the same time. . 2. Both male and female reproductive organs may be 2. Both male and female reproductive organs may be

present, but only one is active and viable at any given time.present, but only one is active and viable at any given time.

Hermaphrodites are mostly found Hermaphrodites are mostly found among invertebrates and plants, few among invertebrates and plants, few fishes and rarely among the higher fishes and rarely among the higher chordates.chordates.

Banana Slugs Earthworms

PLANTS HAVE BOTH MALE & FEMALE PARTS IN THEIR FLOWERS.

Sea bass

Hamlets

Hermaphroditic fish

In birds and mammals, hermaphroditism is usually a pathological condition causing infertility .