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A-level Biology > 8A - Mutations and Cancer (including data) > Flashcards

8A - Mutations and Cancer (including data) Flashcards

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1
Q

What are mutations?

A

Changes to the base sequence of DNA.

Any change to one or more nucleotide bases or any rearrangement of bases in DNA.

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2
Q

What can mutations be caused by?

A

Can arise spontaneously as errors during DNA replication however can be increased by mutagenic agents, e.g. high energy ionising radiation and chemicals.

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3
Q

What can the rate of mutation be increases by?

A

Mutagenic agents.

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4
Q

What are the types of mutations?

A 
Substitution
Deletion
Addition
Duplication
Inversion
Translocation
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5
Q

What is a substitution mutation?

A

One or more bases (nucleotides) are swapped for another different base.

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6
Q

What are the consequences of a substitution mutation?

A

Depending on what base is substituted, there are 3 consequences:

  • Formation of a stop codon, production of the polypeptide would be stopped and protein most likely significantly different, not functional.
  • Formation of a codon for a different amino acid, structure differs slightly so protein would differ in shape and functionality e.g. sickle cell anaemia.
  • Formation of a different codon but same amino acid, genetic code degenerate so most amino acids have more than one codon (no effect on polypeptide and therefore protein).
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7
Q

What is a deletion mutation?

A

One or more bases are removed.

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8
Q

What are the effects of a deletion mutation?

A

Causes a frameshift because each 3 letters of the code has been shifted to the left. Most triplets will be different and therefore the amino acid they code for, non-functional protein produced will significantly alter the phenotype.

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9
Q

What is an addition mutation?

A

One or more bases are added.

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10
Q

What are the effects of an addition mutation?

A

Frame shift to the right.

If 3 bases are inserted it will not have as much of an effect but would still have a different polypeptide.

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11
Q

What is a duplication mutation?

A

One or more bases are repeated.

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12
Q

What are the effects of a duplication mutation?

A

Frame shift to the right.

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13
Q

What is an inversion mutation?

A

A sequence of bases is reversed.

Group of bases (of any number) becomes separated from the sequence then rejoins in the same position but in inverse order.

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14
Q

What are the effects of an inversion mutation?

A

Affects the amino acid produced.

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15
Q

What is a translocation mutation?

A

A sequence of bases is moved from one location in the genome to another. This could be movement within the same chromosome or movement to a different chromosome.

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16
Q

What are the effects of a translocation mutation?

A

Significant effect on gene expression leading to abnormal phenotype, includes the development of certain cancers and reduced fertility.

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17
Q

What can a mutation in a polypeptide that makes up an enzyme cause?

A

May change the shape of the enzyme’s active site. This may stop substrates from being able to bind to the active site, leaving the enzyme unable to catalyse the reaction.

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18
Q

How can some mutations increase the likelihood of developing certain cancers - example?

A

E.g. mutations of the gene BRCA1 can increase the chances of developing breast cancer.

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19
Q

What are hereditary mutations/how do they work?

A

If a gamete (sex cell) containing a mutation for a genetic disorder or a type of cancer is fertilised, the mutation will be present in the fetus formed - so the mutation is passed on to the offspring.

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20
Q

What is it called if a gamete (sex cell) containing a mutation for a genetic disorder or a type of cancer is fertilised, the mutation will be present in the fetus formed - why?

A

Hereditary mutations because they are passed on to the offspring.

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21
Q

What do beneficial hereditary mutations do?

A

Drive evolution.

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22
Q

Which types of mutations may not always cause a change to the amino acid sequence of the polypeptide?

A

Substitution and inversion mutations.

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23
Q

Which types of mutations almost always cause a change to the amino acid sequence of the polypeptide?

A

Additions, duplications and deletions within a gene.

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24
Q

Why do additions, duplications and deletions within a gene almost always cause a change to the amino acid sequence of the polypeptide?

A

Because they all change the number of bases in the DNA code.

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25
Q

What does changing the number of bases in the DNA code cause?

A

A frameshift in the base triplets that follow, so that the triplet code is read in a different way.

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26
Q

What is it called if a mutation doesn’t cause a change in the amino acid order?

A

A ‘silent mutation’.

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27
Q

What is a ‘silent mutation’?

A

If a mutation doesn’t cause a change in the amino acid order.

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28
Q

What are the base triplets that follow on from the mutation said to be?

A

‘Downstream’ of the mutation.

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29
Q

What mutagenic agents increase the rate of mutation?

A
  • High energy ionising radiation - alpha and beta particles as well as short wavelength radiation, e.g. X-rays and UV.
  • Chemicals such as nitrogen dioxide (burning of fossil fuels) and benzopyrene (tobacco smoke).
  • Viruses.
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30
Q

How can mutagenic agents increase the rate of mutation?

A

1) Acting as a base.
2) Altering bases.
3) Changing the structure of DNA.

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31
Q

How do mutagenic agents acting as a base increase the rate of mutation?

A

Chemicals called base analogs can substitute for a base during DNA replication, changing the base sequence in the new DNA.

E.g. 5-bromouracil is a base analog that can substitute for thymine. It can pair with guanine (instead of adenine), causing a substitution mutation in the new DNA.

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32
Q

How do mutagenic agents altering bases increase the rate of mutation?

A

Some chemicals can delete or alter bases.

E.g. alkylating agents can add an alkyl group to guanine, which changes the structure so that it pairs with thymine (instead of cytosine).

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33
Q

How do mutagenic agents changing the structure of DNA increase the rate of mutation?

A

Some types of radiation can change the structure of DNA, which causes problems during DNA replication.

E.g. UV radiation can cause adjacent thymine bases to pair up together.

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34
Q

What are the positives of mutations?

A
  • Produces genetic diversity necessary for natural selection and speciation.
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35
Q

What are the negatives of mutations?

A
  • Harmful.
  • Produce organisms less well suited to its environment.
  • If in body cells leads to disruption of normal cellular activities, such as cell division, can then lead to cancer.
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36
Q

What can mutations in genes cause?

A

Uncontrolled cell growth.

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37
Q

What are mutations that occur in individual cells after fertilisation called?

A

Acquired mutations.

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38
Q

What are acquired mutations?

A

Mutations that occur in individual cells after fertilisation (e.g. in adulthood).

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39
Q

If mutations occur in the genes that control the rate of cell division (by mitosis) what can it cause?

A

Uncontrolled cell division.

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40
Q

What is the result if a cell divides uncontrollably?

A

A tumour.

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41
Q

What is a tumour?

A

A mass of abnormal cells.

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42
Q

What are tumours that invade and destroy surrounding tissue called?

A

Cancers.

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43
Q

What are cancers (what makes them up)?

A

Tumours that invade and destroy surrounding tissue.

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44
Q

How many types of gene control cell division?

A

2

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45
Q

What are the 2 types of gene that control cell division?

A

Tumour suppressor genes and proto-oncogenes.

46
Q

What can mutations in the genes that control cell division cause?

A

Cancer.

47
Q

What is cancer?

A

A group of diseases caused by damage to the genes that regulate mitosis and the cell cycle; leading to unrestricted growth.

48
Q

What does metastasize mean?

A

Move/spread.

49
Q

How can tumour suppressor genes cause cancer?

A

Can be inactivated if a mutation occurs in the DNA sequence meaning the proteins that it normally produces can’t be produced so the rate of cell division increases, resulting in a tumour.

50
Q

Explain the function of tumour suppressor genes

A

They slow down cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis).

51
Q

How do tumour suppressor genes slow down cell division?

A

By producing proteins that stop cells dividing or cause them to self-destruct (apoptosis).

52
Q

What is apoptosis?

A

When cells self-destruct.

53
Q

What happens to cells when tumour suppressor genes become inactivated?

A

Most dies but some clone themselves and go on to form tumours.

54
Q

Explain the function of proto-oncogenes

A

They stimulate cell division by producing proteins that make cells divide.

55
Q

How do proto-oncogenes make cells divide?

A

By producing proteins that make cells divide.

56
Q

What is a mutated proto-oncogene called?

A

An oncogene.

57
Q

What is an oncogene?

A

A mutated proto-oncogene.

58
Q

How can the effect of a proto-oncogene be increased?

A

If a mutation occurs in the DNA sequence.

59
Q

What do oncogenes do?

A

Stimulate a cell to divide when growth factors attach to a protein receptor on its cell surface membrane, activating a gene that tells DNA to replicate and the cell to divide.

60
Q

How can proto-oncogenes cause cancer?

A

They can mutate into oncogenes meaning they become overactive - this stimulates the cells to divide uncontrollably (the rate of division increases) resulting in a tumour.

61
Q

What happens to a proto-oncogene when it mutates into an oncogene?

A

It remains permanently switched on as:
1) The receptor protein is activated so cell division continues even in the absence of growth factors.
2) Oncogene may code for a growth factor which is then produced in excessive amounts and stimulates cell division.
The cell then divides rapidly, causing a tumour (mutations can be inherited).

62
Q

Can mutations be inherited?

A

YES

63
Q

What are the 2 types of tumours?

A

Benign and malignant.

64
Q

Are malignant tumours cancerous?

A

YES

65
Q

Are benign tumours cancerous?

A

NO

66
Q

Describe the size of benign tumours

A

Large (but not as large as malignant tumours).

67
Q

Describe the size of malignant tumours

A

Large

68
Q

How fast do benign tumours grow?

A

Slow-growing.

69
Q

How fast do malignant tumours grow?

A

Fast-growing.

70
Q

Describe the appearance of the nucleus in benign tumours

A

Normal appearance.

71
Q

Describe the appearance of the nucleus in malignant tumours

A

Bigger and darker as holds more DNA (to divide).

72
Q

Do benign tumours undergo differentiation?

A

YES

73
Q

Do malignant tumours undergo differentiation?

A

No - they are differentiated in the process (simpler form).

74
Q

Do benign tumours spread?

A

No - they have adhesion molecules which sticks molecules together so they can’t move.

75
Q

Do malignant tumours spread?

A

Yes - the metastasize (spread) quickly to other parts of the body (and some parts break off).

76
Q

Do benign tumours have a capsule?

A

Yes - makes them difficult to spread.

77
Q

Do malignant tumours have a capsule?

A

No - they have finger like projections which allows them to spread.

78
Q

Are benign tumours life threatening?

A

Can be depending on where they are.

79
Q

Are malignant tumours life threatening?

A

Yes - more life threatening then benign tumours.

80
Q

What size effects on the body do benign tumours have?

A

Localised effects.

81
Q

What size effects on the body do malignant tumours have?

A

Whole body issues.

82
Q

What treatments are there for benign tumours?

A

Removal.

83
Q

What treatments are there for malignant tumours?

A

Chemotherapy, surgery, radiotherapy.

84
Q

What is occurrence of a benign tumour like after removal?

A

Generally won’t come back.

85
Q

What is occurrence of a malignant tumour like after removal?

A

Can come back.

86
Q

Where can cells of a malignant tumour go if they break off?

A

Spread to other parts of the body in the bloodstream or lymphatic system.

87
Q

What are benign tumours often covered in and why?

A

Fibrous tissue that stops cells invading other tissues.

88
Q

Although they are often harmless, what can benign tumours cause/do?

A

Blockages and put pressure on organs.

89
Q

What can some benign tumours turn into?

A

Malignant tumours.

90
Q

In what ways do tumour cells differ from normal cells?

A

1) They have an irregular shape.
2) The nucleus is larger and darker than in normal cells. Sometimes the cells have more than one nucleus.
3) They don’t produce all the proteins needed to function correctly.
4) They have different antigens on their surface.
5) They don’t respond to growth regulating processes.
6) They divide (by mitosis) more frequently than normal cells.

91
Q

What has DNA analysis told us about cancer cells?

A

That they originate from 1 mutant cell leading to uncontrolled mitosis (as a result of the mutations).

92
Q

What does metastasize mean?

A

Move/spread.

93
Q

What is methylation?

A

Adding a methyl (-CH3) group onto something.

94
Q

What is methylation of DNA an important method of?

A

Regulating gene expression.

95
Q

Why is methylation of DNA an important method of regulating gene expression?

A

It can control whether or not a gene is transcribed (copied into mRNA) and translated (turned into a protein).

96
Q

What is hypermethylation?

A

Too much methylation.

97
Q

What is hypomethylation?

A

Too little methylation.

98
Q

How can abnormal methylation (hypermethylation) of cancer-related genes cause tumour growth.

A
  • Happens in the promoter region of the tumour suppressor genes.
  • They are hypermethylated which causes they to become inactive.
  • This means there is no transcription of the promoter region - so the proteins they produce to slow cell division aren’t made.
    (The TSG are silenced - switched off)
  • This means that cells are able to divide uncontrollably by mitosis and tumours can develop.
99
Q

How can abnormal methylation (hypomethylation) of cancer-related genes cause tumour growth.

A
  • Hypomethylation of proto-oncogenes causes them to act as oncogenes (oncogenes are activated) - increasing the production of the proteins that encourage cell division.
  • This stimulates cells to divide uncontrollably, which causes the formation of tumours.
100
Q

What might increased exposure of oestrogen be a result of?

A

Starting menstruation earlier than usual or the menopause later than usual - oestrogen concentrations increase during the menopause.

101
Q

What is increased exposure to oestrogen over an extended period of time thought to increase?

A

A woman’s risk of developing breast cancer.

102
Q

What is thought to increase a woman’s risk of developing breast cancer?

A

Increased exposure to oestrogen over an extended period of time.

103
Q

In what ways is oestrogen thought to contribute to the development of some breast cancers?

A

1) Oestrogen can stimulate certain breast cells to divide and replicate. The fact that more cell divisions are taking place naturally increases the chance of mutations occurring, and so increases the chance of cells becoming cancerous.
2) This ability to stimulate cell division could also mean that if cells do become cancerous, their rapid replication could be further assisted by oestrogen, helping tumours form more quickly.
3) Other research suggests that oestrogen is actually able to introduce mutations directly into the DNA of certain breast cells, again increasing the chance of these cells becoming cancerous.

104
Q

What effect can oestrogen have once a tumour has developed?

A
  • More oestrogen produce, increasing the size of the tumour further.
  • The white blood cells are drawn to the tumour and increase oestrogen production and tumour growth.
  • Oestrogen activates a transcription factor, promoting transcription.
105
Q

What tumour suppressor genes are associated with breast cancer?

A

BRAC1, BRAC2.

106
Q

What tumour suppressor gene is associated with leukemia/(blood cancer)?

A

TP53.

107
Q

How can genetic factors increase a person’s chance of getting cancer?

A

Some cancers are linked with specific inherited alleles. If you inherit that allele you’re more likely to get that type of cancer (but it doesn’t mean you’ll definitely get that type of cancer).

108
Q

How can environmental factors increase a person’s chance of getting cancer?

A

Exposure to radiation, lifestyle choices such as smoking, increased alcohol consumption, and a high-fat diet have all been linked to an increase chance of developing some cancers.

109
Q

What does polygenic mean?

A

When some characteristics are affected by many different genes.

110
Q

Why is knowing the mutation useful for the prevention of cancer?

A

1) If a specific cancer-causing mutation is known, then it is possible to screen for the nutation in a person’s DNA.
2) Knowing about this increased risk means that preventative steps can be taken to reduce it.
3) Knowing about specific mutations also means that more sensitive tests can be developed, which can lead to earlier and more accurate diagnosis.

111
Q

Why is knowing the mutation useful for the treatment of cancer?

A

1) The treatment for cancer can be different for different mutations, so knowing how specific mutations actually cause cancer can be very useful for developing drugs to effectively target them.
2) Some cancer-causing mutations require more aggressive treatment than others, so understanding how the mutation that causes tham works can help produce the best treatment plan.
3) Gene therapy (where faulty alleles in a person’s cells are replaced by working versions of those alleles) may also be able to treat cancer caused by some mutations.

112
Q

What is gene therapy?

A

Where faulty alleles in a person’s cells are replaced by working versions of those alleles.

A-level Biology (42 decks)

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