All cells arise from other cells Flashcards

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1
Q

What is mitosis?

A

A division of a cell that results in two daughter cells having an exact copy of the DNA of the parent cell.

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2
Q

How does cell division take place?

A

Either by:
Mitosis - produces 2 daughter cells with the same number of chromosomes as the parent cell and each other.
Meiosis - produces 4 daughter cells, each with half the number of chromosomes of the parent cell.

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3
Q

What is interphase?

A

The period following mitosis where the cell is not dividing.
It occupies most of the cell cycle.
Lots of cellular activity, including the replication of DNA.

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4
Q

What are the four stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

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5
Q

What is prophase?

A

The chromosomes shorten and thicken (condense) and become visible.
Centrioles move to opposite ends of the cell and spindle fibres develop from them.
Collectively, these are called spindle apparatus.
The nucleolus disappears and the nuclear envelope breaks down.
The chromosomes are left freely in the cytoplasm.
The chromosomes are drawn to the equator of the cell by the spindle fibres.

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6
Q

What is metaphase?

A

The chromosomes are seen to be made up of 2 chromatids.
Each chromatid is an identical copy of DNA from the parent cell.
The chromatids are joined by the centromere.
The chromosomes are pulled along the spindle apparatus by the centromere and arrange themselves along the equator of the cell.

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7
Q

What is anaphase?

A

The centromeres divide into two and the spindle fibres pull the individual chromatids apart.
The chromatids move to their respective poles and are now referred to as chromosomes.
The energy required is provided by the mitochondria, which gather around the spindle fibres.

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8
Q

What is telophase?

A

The chromosomes reach their respective poles and become longer and thinner, finally disappearing completely, and leaving widespread chromatin.
The spindle fibres disintergrate and the nuclear envelope and nucleolus re-form.
The cytoplasm divides through cytokinesis.

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9
Q

How does cell division happen in prokaryotic cells?

A

Binary fission:
The circular DNA molecule replicates and both copies attach to the cell membrane.
The plasmids also replicate.
The cell membrane begins to grow between the two DNA molecules and pinches inwards, dividing the cytoplasm in two.
A new cell wall forms between the two DNA, dividing the cell into two identical daughter cells.
They each have a single copy of the circular DNA and a variable number of copies of the plasmids.

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10
Q

What is mitosis used for?

A

Growth
Repair
Reproduction

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11
Q

Which cells have a cell cycle?

A

Cells that do not divide continuously but undergo a regular cycle of division separated by periods of growth.

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12
Q

What is the first stage of the cell cycle?

A

Interphase - it occupies most of the cycle (about 90%).
It is sometimes known as the resting place as no division takes place.

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13
Q

What is the second stage of the cell cycle?

A

Nuclear division - when the nucleus divides either into two or four.

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14
Q

What is the third stage of the cell cycle?

A

Cytokinesis - the cytoplasm divides to produce two or four new cells.

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15
Q

How long is the cell cycle?

A

Complete cell cycle length varies between organisms.
Typically, a mammalian cell takes about 24 hours, 90% of which is interphase.

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16
Q

What is cancer?

A

A group of diseases caused by a growth disorder of cells.
It is the result of damage to the genes that regulate mitosis and the cell cycle.
This leads to uncontrollable growth and division of cells.
The cells can reject apoptosis (the cell naturally killing itself) and keep mutliplying.

17
Q

What are tumours?

A

A group of abnormal cells that develop and constanly expand.

18
Q

Where do tumours form?

A

Can develop in any organ in the body but most commonly:
The lungs
Prostate gland
Breasts and ovaries
Large intestine
Stomach
Oesophagus
Pancreas

19
Q

When are tumours cancerous?

A

When they develop from benign to malignant.

20
Q

What are malignant tumours?

A

They grow rapidly
Less compact
More likely to be life-threatening

21
Q

How is cancer often treated?

A

It often involves killing dividing cells by blocking part of the cell cycle.
The cell cycle is disrupted and cell division, and hence, cancer growth ceases.

22
Q

How is the cell cycle disrupted?

A

Drugs - chemotherapy - prevent the DNA from replicating.
Inhibits the metaphase stage of mitosis by interfering with spindle formation.

23
Q

What is the disadvantage with chemotherapy?

A

They also disrupt the cell cycle of normal cells.
For example, hair-producing cells, that divide rapidly, are also vulnerable to damage, and therefore hair loss is frequent in cancer patients.

24
Q

What is the advantage with chemotherapy?

A

The drugs are more effective against rapidly dividing cells.
Cancer cells have very fast rate of division, so are damaged to a greater degree than normal cells.

25
Q

How do mutations affect mitosis?

A

A mutation to one of the genes controlling mitosis causes uncontrolled mitosis.
The mutant cells are usually structurally and functionally different.
Most mutated cells die.
But those that survive are capable of dividing to form clones of themselves and form tumours.

26
Q

What is cell specialisation?

A

Cells are specialised to perform specific functions.
Depending on their function, cells have developed to have more or less of certain cells.