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Human Biology Y11 > cell division > Flashcards

cell division Flashcards

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1
Q

cell cycle

A

new cells are needed to replace old, dead or damaged cells

the events that take place from one cell division to the next are called the cell cycle, keeps repeating as the cell divides again and again

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2
Q

phases in the cell cycle

A
  • G1 phase
  • S phase
  • G2 phase
  • ## M phase
  • G0 phase
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3
Q

G1 phase

A

G1 phase: or first growth phase - the cell produces new proteins, grows and carries out its normal tasks for the body; this phase ends when the cell’s DNA begins to duplicate

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4
Q

S phase

A

S phase: or synthesis phase - DNA replication, the DNA molecules in the cells nucleus form exact copies of themselves

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5
Q

G2 phase:

A

G2 phase: or second growth phase - this relatively short phase involves preparation for cell divisions

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6
Q

M phase

A

M phase: or mitotic phase - the cell divides into two daughter cells

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7
Q

after division

A

After division, cells may continue the cell cycle and re-enter G1 phase.

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8
Q

G0 phase

A

some cells leave the cycle and stop dividing for days, years or even for the rest of the person’s life. These cells are in G0 phase.

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9
Q

mitosis purpose

A

Cells must divide for overall growth of an organism, as well as for the replacement and repair of damaged or worn out cells. Purpose of mitosis is to produce two identical daughter cells with diploid number of chromosomes for replacement of cells due to wear or damage

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10
Q

process of mitosis

A
  • Interphase
  • Metaphase
  • Prophase
  • Anaphase
  • Telophase
  • Cytokinesis
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11
Q

interphase

A

during this phase, the cell goes through the G1, S and G2 phase. Most of this phase the cell is carrying out its normal cellular functions. Toward the end of this phase the DNA is copied (DNA replication occurs) and the centriole in the cytoplasm also replicates.

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12
Q

prophase

A

the phase of mitosis in which the duplicated DNA strands condense (coiling) and form structures called chromosomes, the nucleolus disappears, the nuclear membrane breaks down, and 2 centrioles move to opposite ends of the cell. Spindle fibres (microtubules) form between the centrioles.

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13
Q

metaphase

A

the phase of mitosis in which the chromosomes attach to the spindle fibres and line up at the equator (the central plane) of the cell.

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14
Q

anaphase

A

the phase of mitosis in which the spindle fibres contract pulling on the chromosomes until they separate into individual chromatids, moving towards opposite ends of the cell.

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15
Q

telophase

A

the last phase of mitosis, when the chromatids migrate to opposite ends of the cell, two new nuclear membranes form around each group of chromatids, and the chromatids uncoil back into DNA strands.

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16
Q

cytokinesis

A

division of cytoplasm, this is basically when the cell divides into two new daughter cells.It is not considered a phase of mitosis.

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17
Q

cell classification

A

Cells can be classified as either stem cells or specialised cells. In general, specialised cells are unable to divide. Therefore, they must be replaced by other means. When stem cells undergo mitosis, the daughter cells may be new stem cells (stem cell proliferation) or cells that differentiate to form specialised cells.

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18
Q

differentiation

A

Mitosis ensures that each daughter cell receives the same genes that were in the parent cell. Therefore, every cell in a person’s body has the same genetic information.

  • cells are specialised so that they can carry out particular tasks. The process by which cells become specialised is called differentiation. it seems that as the cells undergo division by mitosis, different genes become activated.
  • This makes the cells differentiate into specialised cells that can perform particular functions - for example, stomach cells that secrete enzymes, muscle cells that can contract, or red blood cells that can carry oxygen
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19
Q

stem cells

A
  • The cells that can undergo differentiation are called stem cells. They are very different from other cells because they are not specialised for any particular role and are capable of repeated division by mitosis.
  • In the right conditions, stem cells can differentiate into specialised cells.
  • Because stem cells have the potential to develop into any cell type, they could possibly provide an unlimited source of cells for repair of tissues such as bone, skin, muscle, liver or blood.
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20
Q

how are stem cells classified?

A

Stem cells can be classified based on where they originate (embryonic, adult or cord blood) or the type of cells that they can form.

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21
Q

stem cell classifications

A
  • totipotent
  • pluripotent
  • multipotent
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22
Q

totipotent stem cells

A

Totipotent stem cells have the potential to create any type of cell necessary for embryonic development, including the embryo itself and all the membranes associated with embryonic development. The cells of the embryo within the first couple of mitotic divisions after fertilisation are the only totipotent cells.

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23
Q

pluripotent stem cells

A

Pluripotent stem cells can give rise to any of the cells in the body. Embryonic stem cells are pluripotent as they differentiate to form all cells of the individual.

24
Q

multipotent stem cells

A

Multipotent stem cells have the potential to form a number of different types of cells. For example, blood stem cells give rise to red blood cells, white blood cells and platelets, whereas skin stem cells give rise to the different types of skin cells. Embryonic stem cells, adult stem cells/somatic cells and cord blood stem cells are multipotent

25
Q

meiosis

A

Meiosis produces gametes for reproduction and involves DNA replication, chromosome pairing, and two successive nuclear divisions distributing haploid sets of chromosomes to each gamete

26
Q

interphase I

A

the DNA replicates

27
Q

prophase I

A

the DNA coils and individual chromosomes become visible and go into homologous pairs

28
Q

metaphase I

A

each pair of homologous chromosomes line up and exchange genetic material during crossing over. Either maternal or paternal homologue may orientate towards either pole. This creates variation.

29
Q

anaphase I

A

spindle fibres pull one chromosome from each homologous pair towards opposite poles of the cell. Each pole ends up with one copy of each chromosome. The cell now has half the number of chromosomes. (haploid). There are no longer any chromosome pairs.

30
Q

telophase I

A

the nuclear membrane reforms

31
Q

prophase II

A

spindle fibres form and attach to each of the chromatids.

32
Q

metaphase II

A

the chromosomes line up along the equator of the cell.

33
Q

anaphase II

A

the spindle fibres contract and pull one chromatid from each chromosome to opposite ends of the cell.

34
Q

telophase II

A

the cell divides through forming 4 nuclei each with half the number of chromosomes as the parent cell.

35
Q

mitosis vs meiosis

A

number of nuclear divisions:
Mitosis: 1, Meiosis: 2

number of daughter cells produced
Mitosis: 2, Meiosis: 4

crossing over occurs:
Mitosis: No, Meiosis: Yes

location
Mitosis: somatic cells, Meiosis: gonads (reproductive organs)(testes and ovaries)

function:
Mitosis: growth and repair, Meiosis: production of gametes

number of chromosomes in daughter cells:
Mitosis: 46 (2n), Meiosis: 23 (n)

homologous chromosomes pair up in:
Mitosis: No, Meiosis: Yes

variation is produced:
Mitosis: No, Meiosis: Yes

36
Q

human variations as a result of:

A
  • crossing over
  • independent assortment
  • non-disjunction
  • random fertilisation
37
Q

crossing over

A
  • during metaphase 1
  • chromatids may break and exchange segments in homologous chromosome pairs
  • this results in a new combination of genes along the chromosome, this is called recombination
38
Q

non-disjunction

A
  • during anaphase 1 and 2
  • one or more homologous pairs of sister chromatids may fail to separate when the cell divides
  • this results in once daughter cell with an extra chromosome and one daughter cell lacking a chromosome
  • changed to the chromosome number can cause severe birth defects and miscarriage early in the pregnancy
  • trisomy - an extra copy of a chromosome (3 instead of 2) e.g trisomy 21
  • monosomy - missing a chromosome (1 instead of 2)
39
Q

random assortment

A
  • during metaphase 1
  • chromosomes have a random orientation of homologous pair and move randomly to separate poles during meiosis
  • this results in a gamete with genes arranged in an order that has never occurred before and will never occur again
40
Q

random fertilisation

A
  • any egg with any sperm
41
Q

cancer

A

Normally, the division of cells is controlled. However, under certain conditions this control is lost, and the cells divide uncontrollably. This condition is known as cancer. This uncontrolled growth of abnormal cells produces a mass, or tumour as this process may occur in almost any type of tissue. there are many different types of cancer - for example, breast cancer, brain cancer, leukaemia, lung cancer and skin cancer.
Cancer cells do not differentiate into the normal tissue cells that surround the tumour. They can therefore be easily identified with a microscope.

42
Q

malignant tumours

A

Some tumours are malignant, which means the tumour cells are able to spread to other parts of the body. This is known as metastasis. in this way, secondary tumours may develop in parts of the body well away from the original tumour.

43
Q

benign tumours

A

Some tumours are not malignant as they are not able to invade normal tissues, blood or lymph vessels and so do not spread to other parts of the body. these tumours are called benign. benign tumours grow and press on surrounding tissues. Such tumours can be dangerous if they exert pressure on organs such as the brain. However, because a capsule often surrounds them. they are usually easily removed.

44
Q

causes of cancer

A

While the cause of some cancers is unknown, we do know that certain environmental factors called carcinogens can trigger malignant tumours. Cancer usually occurs only after long exposure to a carcinogen, and the cancer may develop many years after the exposure has ended. Other factors, such as genetics, can also affect the likelihood of developing cancer.

45
Q

carcinogens

A

A great many substances and forms of radiation have been found to be associated with cancers.

46
Q

types of carcinogens

A
  • ultraviolet (uv) radiation
  • x-rays
  • ionising radiation
  • viruses
  • chemical carcinogens
47
Q

carcinogen: ultraviolet radiation

A

Ultraviolet (v) radiation, which is a part of sunlight, produces cancer of the skin, especially in people with light-coloured skin. Sunburn and overexposure to UV radiation are the main causes of skin cancer.

48
Q

carcinogen: x-rays

A

X-rays are Known to cause cancer. In Australia, exposure to X-rays is limited and controlled. The amount of radiation produced by modern machines poses little risk to patients from routine medical use.

49
Q

carcinogen: ionising radiation

A

lonising radiation, such as that produced by radium and ores of uranium, can cause cancer. A single exposure to a high dose may result in leukaemia. Radiation from the atomic bombs dropped on Hiroshima and Nagasaki in Japan at the end of World War caused a significant increase in the incidence of cancers in the people of those cities.

50
Q

carcinogen: viruses

A

Viruses have been found to cause some forms of cancer. For example, the human papilloma virus (HPV) causes cancer of the cervix in women. A vaccine called Gardasil® that protects young women against some forms of HPV was introduced in Australia in 2007.

51
Q

chemical carcinogens

A

Chemical carcinogens are widespread in modern society, but simple precautions can usually be taken to avoid excessive exposure. Some Known chemical carcinogens are alcohol (excessive consumption), asbestos, soot and tar, organic solvents in glues and paints, and tobacco tar.

52
Q

prevention of cancer

A

Many cancers are associated with lifestyle factors, such as exposure to UV radiation, smoking, alcohol consumption and diet.
In Australia, the incidence of cancer has been reduced in two ways:
- by education
- by legislation

by taking positive steps

53
Q

reduction of cancer: by education

A

The public has been made aware, through advertising and other education programs, of the need to limit exposure to carcinogens. An example was the very successful Slip!
Slop! Slap! program, introduced in 1981, to make people aware of the need to limit exposure of the skin to Uv radiation. This message has now been expanded to ‘Slip! Slop! Slap! Seek! Slide!.

54
Q

reduction of cancer: by legislation

A

Australian governments have passed laws to control exposure to carcinogens. For example, smoking is banned in most public places, advertising of tobacco is not permitted, and cigarettes must be sold in plain packaging with graphic health warnings. Standards have been imposed for the manufacture and operation of X-ray machines, and products containing asbestos have been banned. These and other measures have helped to reduce the incidence of cancer, but each of us still has a responsibility to minimise our own risks as far as possible.

55
Q

positive steps to take to reduce the risk of cancer

A
  • Avoid smoking.
  • Use sunscreen, sunglasses, long-sleeved clothing, shade and hats to reduce exposure to UV radiation.
  • If possible, stay out of direct sunlight between 10 a.m. and 5 p.m.
  • Ensure that your diet has adequate fibre.
  • Avoid being overweight or obese.
  • Limit alcohol intake, if you choose to drink.
  • Use protective clothing and a face mask when handling chemicals such as organic solvents or vinyl chlorides.
56
Q

early detection

A

Early Detection of cancer is critical for successful treatment of the disease, there are several tests that can detect cancer.

57
Q

individual responsibility

A

Individuals should be familiar with their own body and should see a doctor if any suspicious change is noticed.
For example, a breast lump, a lump in a testicle, a change in a mole, a change in bowel or bladder habits, any sore that does not heal, persistent cough or hoarseness, or indigestion or difficulty swallowing could be an indication of cancer.

Human Biology Y11 (15 decks)

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