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AS Biology > CELLS : Mitosis/Cancer > Flashcards

CELLS : Mitosis/Cancer Flashcards

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1
Q

What is mitosis?

A

Cell division that results in each of the daughter cells having exact copies of the DNA of the parent cell.

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2
Q

What are the products of mitosis?

A

Two daughter cells that have genetically identical nuclei to the parent cell.

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3
Q

What is mitosis needed for?

A
  • Growth of multicellular organisms.
  • Repairing damaged tissues.
  • Reproduction in single-celled organisms.
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4
Q

Draw the cell cycle:

A
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5
Q

What does the cell cycle consist of?

A
  • Cell growth and DNA replication called interphase.
  • Mitosis
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6
Q

What is interphase subdivided into?

A

Three seperate growth stages:

  • Gap phase 1 = cell grows and new organells and protiens are made.
  • Synthesis = cell replicates its DNA, ready to divide by mitosis.
  • Gap phase 2 = cell keeps growing and proteins needed for cell division are made.
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7
Q

What are the four stages of mitosis?

A
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
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8
Q

What type of process is mitosis?

A

A continuous one.

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9
Q

What happens during interphase?

A
  • Cell carries out normal functions, but is preparing to divide.
  • DNA is unravelled and replicated, to double its genetic content.
  • Organelles also replicated so it has spare ones, and ATP content is also increased.
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10
Q

What does ATP do?

A

Provides the energy for cell division.

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11
Q

What happens during prophase?

A
  • Chromosomes condense and become visible, getting shorter and thinner.
  • Centrioles move to opposite poles.
  • Spindle fibres develop from the centrioles, forming spindle apparatus.
  • Nucleolus disappears and nuclear membrane breaks down, leaving chromosomes free in the cytoplasm of the cell.
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12
Q

What are centrioles?

A

Organelles within an animal cell, that spindle fibres develop from.

They are made of tiny bundles of protein.

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13
Q

What are spindle fibres collectively known as?

A

Spindle apparatus.

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14
Q

How do we know centrioles are clearly not essential to spindle fibre formation?

A

Plant cells lack centrioles yet still develop a spindle apparatus.

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15
Q

What happens during metaphase?

A
  • Chromosomes line up along the equator of the cell, pulled by microtubules from the poles.
  • They are attached to the spindle apparatus by their centromere.
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16
Q

What happens during anaphase?

A
  • Centromeres divide into two, separating each pair of sister chromatids.
  • Spindle fibres contract, pulling chromatids to opposite poles of the spindle, centromere first.
  • Chromatids now appear as v-shapes.
17
Q

What provides the energy for anaphase?

A

The mitochondria, which gathers around the spindle fibres.

18
Q

What happens during telophase?

A
  • Chromatids reach opposite poles on the spindle.
  • They uncoil and become long and thin again - now known as chromosomes again.
  • Eventually, they disappear altogether leaving only widely spread chromatin.
  • Nuclear envelope reforms, so there are two nuclei.
  • Cytoplasm divides through cytokinesis.
19
Q

What is chromatin?

A

A mass of material found in the nucleoplasm that contains the genes of the organism.

It separates into chromosomes during cell division.

20
Q

What are the two strands of the chromosome joined by?

A

The centromere.

21
Q

What are the separate arms of a chromosome called?

A

Chromatids.

22
Q

As mitosis begins, why does each chromosome have two strands?

A

Because they have already made an identical copy of themself during interphase.

23
Q

How long does each stage of mitosis take?

A

It varies for each stage.

Therefore, we must calculate it.

24
Q

How do you calculate the length of each stage of the cell cycle?

A
  • Count how many cells are undergoing mitosis.
  • Count how many cells are in the specific stage of mitosis.
  • Divide number of cells in specific stage by total number of cells undergoing mitosis - this suggests the proportion of time the cells spend in the specific stage of the cell cycle.
  • Convert the cell cycle duration into minutes.
  • Times this number by your calculated fraction.
25
Q

What are the three stages of the cell cycle?

A
  • Interphase
  • Nuclear division
  • Cytokinesis
26
Q

What is cancer a result of?

A

Damage to genes that regulate mitosis and the cell cycle.

This leads to uncontrolled growth and division of cells.

27
Q

What is cancer?

A

A group of diseases caused by uncontrollable cell division.

28
Q

What is a tumour?

A

A group of abnormal cells resulting from uncontrollable growth and division of cells.

It becomes cancerous if it changes from benign to malignant.

29
Q

Describe how mitosis can lead to the formation of a tumour:

A
  • Mitosis is how most cells divide.
  • It is controlled by two genes.
  • A mutation in one of these results in uncontrolled mitosis.
  • Mutant cells mostly die.
  • However, some survive and are capable of dividing to form clones of themselves.
  • This forms tumours.
30
Q

What is the difference between malignant and benign tumours?

A
  • Malignant tumours grow rapidly, whereas benign ones grow more slowly.
  • Malignant tumours can spread to other tissues, whereas benign tumours are more compact.
  • Malignant tumours are more likely to be life-threatening, whereas benign tumours are less likely to be life-threatening.
31
Q

What is the treatment of cancer designed to do?

A

Control the rate of cell division by disrupting the cell cycle.

This kills the tumour cells, and hence cancer growth ceases.

32
Q

What are the problems with cancer treatments?

A
  • Also disrupt the cell cycle of normal cells (although they are more effective in the cell cycles of cancer cells, as they divide more often).
  • Common body cells killed are those that divide rapidly, eg hair-producing cells.

This explains the hair loss frequently seen in patients undergoing chemotherapy.

33
Q

Describe some cell cycle targets of cancer treatments?

A
  • G1 (cell growth and protein production) - chemotherapy prevetns the synthesis of enzymes needed for DNA replication. So the cell is unable to enter the synthesis phase (S), disrupting cell cycle and forcing cell to be killed.
  • S phase (DNA replication) - radiation and some drugs damage DNA. This means at checkpoints before and after S phase, severe damage of DNA is detected, so the cell is killed - preveting further tumour growth.

AS Biology (51 decks)

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