Chapter 14 - The Cell Cycle

Question 1

Why do cells need to be reproduced?

Answer 1

1. New cells are produced so damaged, diseased, dead or worn out cells can be replaced
   The more WEAR AND TEAR on a cell - the shorter cell lifespan
2. Body Growth = due to increase in the number of cells
   Eg reproduction of cells = more cells - therefore organs can grow larger

Question 2

Study the average lifespan of human cells

Answer 2

Study the Table

Question 3

What is the cell cycle?

Answer 3

The cells cycle refers to the events that take place from cell division to the next.

Is a cycle because events keep repeating as cell divides again and again

Question 4

What are (4 + 1 extra) phases of the cell cycle?

Answer 4

G1 phase - 1st GROWTH phase - cell produces new proteins, grows and carries out it’s normal tasks for the body.
Phase ends when the cell’s DNA begins to duplicate.

S phase - SYNTHESIS phase - DNA molecules in cell nucleus forms exact duplicates of themselves.

G2 phase - 2nd GROWTH phase - relatively short phase which involves preparation for cell division.

M phase - MITOTIC phase - cell divides into two daughter cells

• cells continue the cycle and enter G1 phase again
• G0 phase - some cells leave the cell cycle and stops dividing for days, years or even for the rest of the person’s life

Question 5

Why is it necessary that DNA is duplicated exactly into daughter cells?

Answer 5

When new cells known as daughter cells are produced it is vital that they contain the same genetic information as the parent cell for the following reasons

• DNA is a molecule which colours in the nucleus of cell which determines the types of protein a cell can make
• protein are structural materials of a cell, and DNA determines the structure of the cell and because the body is made up of cells, the DNA therefore determines the structure of the whole body
• DNA codes for particular cell functions and the way in which the body functions
• enzymes are proteins, so DNA determines which enzymes cell makes and therefore determines the chemical reaction that occur inside and outside of the body cells.

Question 6

What is Mitosis

Answer 6

Mitosis is the process of cell division to produce cell - in which two daughter cells are produced which have the same identical genetic information present in them as the parent cell. ( same Type and number of chromosomes as the parent cell)

Through mitosis the body cell receives exact same heritage material (DNA) possess by the parent cell.

IPMAT= 4 stages **however process is continuous; does not occur in steps

Note; although the term ‘mitosis’ is commonly used to refer to cell division, it technically refers just to the division of the nucleus

Question 7

Explain INTERPHASE in detail

Answer 7

** DNA molecules duplicate**

• It is pre mitosis ( Period between nuclear divisions)
• Cell growth occurs = cells goes through the G1, S and G2 phases
• In S phase - DNA molecules in nucleus form exact copies of themselves thus in this Period the quantity of the DNA molecules doubles - cell a little large

Question 8

Explain PROPHASE in detail

Answer 8

• Nucleoli disappear and nuclear membrane breaks down
• centrioles become visible migrate to opposite poles and microtubules begin to radiate from them
  DNA tightly coils to become chromosomes and them appear as pairs of chromatids joined by a centromere ( are identical tightly coiled DNA)
• spindles form- because the centrioles have reached the end poles and some of the microtubules radiating from them join to form a framework of fibres = spindle
• 1st phase of mitosis

Question 9

Explain METAPHASE in detail

Answer 9

When the nuclear membrane has complete broken down (ending stage of Prophase)

* chromosomes line up on the spindle at the equator of the cell*

• The Chromatid pairs migrate towards the middle (equator) of the cell
• the Chromatid pairs line up on the equator of the spindle
• centromere of each pair is attached to a spindle fibre

Question 10

Explain ANAPHASE in detail

Answer 10

Centromeres divide; chromosomes move to opposite ends of the spindle

• each pair of chromatids separates at the centromere
• the chromatids have become independent of each other and are now called chromosomes
• new chromosomes are then pulled apart towards opposite poles of the cell
• centromeres are still attached to the spindle fibres and it seems that the spindle fibres pull these chromosomes apart in some way

Question 11

Explain TELOPHASE in detail

Answer 11

• Spindle fibres disappear;
• nuclear membranes forms
• nucleolus appears in each new nucleus
• centrioles divide,
• chromosomes uncoil and disappear to become chromatin threads once more;
• cytokinesis begins

Question 12

Explain CYTOKINESIS in detail

Answer 12

• cytoplasm of the cell divides into two, each with nucleus
• occurs during events of telophase
• cytoplasm begins to divide = known as cytokinesis
• furrow develops in the cytoplasm between the two nuclei which gradually deepens until it cuts the cytoplasm into 2 parts ; each with its own nucleus

Question 13

What is produced after mitosis

Answer 13

Mitosis and cytoplasmic division results in TWO DAUGHTER CELLS (two new cells produced from the parent cell) which are now in interphase

Because each chromosome was duplicated and becaus the duplicates have separated into daughter cells - each daughter cell has exactly the same number and Theo of chromosomes as the parent cell — therefore the genetic information is passed on completely and without change from parent cell - daughters

Question 14

Draw and understand the mitosis stages

Answer 14

From book and the photo

Question 15

What is cancer?

Answer 15

An uncontrolled/unrestrained growth; one that has the capability of spreading to other body parts

• not just one Disease but many (collective term for many)
• results from a situation where the normal differentiation of cells goes wrong
• an abnormal mass of tissue called TUMOUR results from uncontrollable division of cells
• cancer cells do not differentiate into normal tissue cells that surround the tumour
• Can be easily identified under a microscope because they look different

Question 16

What are the different types of tumours?

Answer 16

an abnormal mass of tissue called TUMOUR results from uncontrollable division of cells

1. MALIGNANT - the tumour cells are able to spread to other parts of the body
   * METASTASIS = secondary tumours developing in other parts of the body a well way away from the original tumour
2. Benign = tumours that grow and press on surrounding tissues
   Because the cells in the dividing mass are not able to invade normal tissues, blood or lymph vessels and so do not spread to parts of the body.
   * such tumours can be dangerous if they except pressure on vital organs such as Brain.
   * however since a capsule often surround them, they are usually easily removed.

Question 17

What causes Cancer?

Answer 17

Cause of some cancers are unknown, however it is known that certain environmental factors can trigger Malignant tumours.
Such factors are called CARCINOGENS.

Cancer usually only occurs after long exposures or high amounts of exposure to a carcinogen
- and the cancer may develop many years after the exposure has ended.

CARCINOGEN: a cancer causing agent

Question 18

List and explain the (5) carcinogens that are cancer causing.

Answer 18

1. Ultraviolet (UV) radiation - part of sunlight, provides cancer of the skin, especially in people with light-coloured skin.
   * sunburns and overexposure to UV radiation are the main causes of skin cancer.
2. X-rays - are known to cause cancer. In Australia, exposure to x-rays are limited and controlled.
   * amount of radiation produced by modern machines poses little risk to patients from routine medical use.
3. Ionising radiation. Produced by radium and ores of uranium.
   - a single exposure to a high dose may result in LEUKAEMIA.
   Eg, atomic bombs dropped on HIROSHIMA and NAGASAKI in japan at end of WW2 caused a significant increase in the incidence of cancers in the people of those cities.
4. Viruses - have been found to cause some forms of cancer
   Eg Human Papillomavirus (HPV) causes cancer of the cervix in women (cervix is the neck of the uterus).
   A vaccine called GARDASIL that protects young women against some forms of HPV (was introduced in Aus in 2007)

5. Chemical Carcinogens - are widespread in modern society but simple precautions can usually be taken to avoid excessive exposure.
Known chemical carcinogens include 
* alcohol (excessive consumption)
* asbestos 
* soot
* tar 
* organic solvents I’m glued and paints 
* tobacco ta

Question 19

How To prevent cancer Aus.

Answer 19

In Aus incidents of cancer have been reduced in 2 ways
1. Education; made the public aware through advertising and other education programs of the need to limit exposure to the carcinogens.
Eg ‘Slip!,Slop!,Slap!’ Program to make people aware of the need to limit exposure of the skin to UV radiation.

2. Legislation - Aus gov passed laws to control exposure to carcinogens
   * Eg smoking is banned in public areas, advertising of tobacco is not permitted, cigarettes must be sold in plain packaging
   * Eg standards have been imposed for the manufacture and operation of X - ray machines d
   * Eg Asbestos banned

Theses are measures used which have helped to reduce the incidence of cancer

2. Legislation

Question 20

What are some positive steps to do individually to reduce the risk of cancer? (7)

Answer 20

1. Avoid smoking
2. Use sunscreens, sunglasses, long-sleeved clothing, shade and hats to reduce UV exposure
3. If possible stay out of direct sunlight between 10am - 3pm
4. Ensure that diet has adequate fibre and low fat
5. Avoid being overweight or fat
6. Limit alcohol intake
7. Use protective clothing and face mask when handling chemicals such as organic solvents or vinyl chlorides

Question 21

What are the most common cancer caused deaths in Aus (men and women)

Answer 21

1 in 2 men and 1 in 3 women will be diagnosed with cancer by the age of 85. * early detection important for successful treatment of disease.

Women most common cancers and deaths causes

1. Lung
2. Breast
3. Bowel (colorectal)

Men most common cancer and causes deaths

1. Lung
2. Prostate
3. Bowel (colorectal)

Question 22

What is Cervical cancer? And what are the medical treatments for it.

Answer 22

• any women who had sex at any time of life can have risk of cancer of cervix

Cervical cancer is caused by HPV transmitted by genital skin contact through sex.

• most cases the infection clears up naturally (8-14months)
• most people are infected with HPV at once in their life but never know it
• if HPV persistently comes back up, in a number of women the infection does not get clear by body and abnormalities I’d cervical cells can develop.

Treatment / medical support
1928 Dr George Papanicolaou (Greek Born in USA) discovered changes occur in cervical cells before becoming cancerous.
He created a simple test for theses cells called Pap test

Pap test - some cells are collected from cervix and smeared on microscope slide, and examined for abnormalities.
Does not diagnose cancer; only detects early changes in cervical cells that may develop to cancer. Early treatment for cancer is then possible.

Pap smear - every 2 yrs can prevent up to 90% (common forms of cervical cancer and now most is preventable and curable.

New test - tests for the HPV virus present, taken every 5 yrs

Question 23

What is Breast Cancer. And medical treatments are there?

Answer 23

Most common in women and 2nd most cancer for causing deaths in women.
- tumour in breast

Since 1991 Breast Screen Aus has run screening program for Aus women - targeted 50 to 74 age. However 40-49 and 75+ can also take part

Screening is done by MAMMOGRAPHY; an X-ray of breasts.
The X- ray results in a mammogram = X-ray picture on which tumours as small as 1cm in diameter can be detected
* digital mammography uses computer instead of X-ray film to record images of breast.

Question 24

What is bowel Cancer and Treatment for it.

Answer 24

Bowel Cancer or Colorectal Cancer is a malignant tumour that develops in the large intestine - colon or rectum.

Can be successful treated if diagnosed early - but no symptoms and fewer than 40% of bowel cancers are detected in early stages

Medical support

• Australian turning 50,55,60,65 yrs can take part in Bowel Cancer screening program. (Extends to 70 yr old in 2015)
• eligible person is sent a test by mail called FAECAL OCCULT TEST (FOBT).

FOBT - tests for blood in faeces, done at home and sent to laboratory for analysis. With this very small amounts of blood - not visible to eye can be detected.

Blood in Faeces can come from Polyps or from Bowel Cancer.
POLYPS = small growths inside the colon or rectum.
Most bowel cancers develops from polyps, although not all polyps are cancerous. Removal of polyps - reduces risk of bowel cancer.

If FOBT test is (+) patients are referred to colonoscopy, a visual examination of the inside of the large intestines using an instrument called a colonoscope.

Question 25

What is Prostate Cancer and What is the Medical Support Offered?

Answer 25

Many prostate cancers grow very slowly and do not require any treatment but other forms are life-threatening because they grow and spread rapidly.

• no screening because it showed little benefit
• no test distinguishing between the rapid and slow occurring cancers

Treatment
- aggressive prostate cancer can be cured if diagnosed while it is still confined to prostate gland.
The three methods include

1. DIGITAL RECTAL EXAMINATION (DRE)
   - doctor inserts a gloved finger into anus, from where it is possible to feel part of the surface of prostate gland.
   - any swelling, hardening or irregularities of the surface may indicate cancer
   * problem is that only part of the prostate surface can be felt therefore some irregularities may be beyond reach
2. PROSTATE SPECIFIC ANTIGEN (PSA)
   - Test checks the blood for presence of a particular protein produced by the prostate gland. If the PSA is rising it may indicate the presence of a prostate tumour.
3. BIOPSY
   - if PSA and DRE indicates possibility of cancer, then a biopsy can be performed.
   - BIOPSY= is a small sample tissue that can be checked for cancer cells.
   - a spring loaded needle is used and several samples are taken from the prostate gland, while patient is under General anaesthetic
   - samples are examined to determine the presence of tumour cells, if present what type. * then decision about treatment

• diagnostic procedures do Have side effects and limitations

Question 25

When should you check for cancer

Answer 25

Any suspicious change in body occurs

• breast lump,
• lump in testicles
• change in a mole
• change in bowel or bladder habits
• sore that does not heal
• persist cough or hoarseness
• indigestion or difficulty swallowing
• unusual bleeding
• check skin regularly
• women - Pap test 2yrs, talk about cervical cancer vaccine
• men - prostate check (50)
  Over 50 - mammogram, regular tests for bowel cancer