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Biology A-level > 8A Mutations and Gene Expression > Flashcards

8A Mutations and Gene Expression Flashcards

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1
Q

How can hypomethylation lead to cancer?

A

It switches on the oncogene

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2
Q

Which type of tumourc an metastatise?

A

Malignant

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3
Q

Give an example of where you may find a multipotent stem cell

A

Bone marrow

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4
Q

What is the science of collecting and analysing complex biological data called?

A

Bioinformatics

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5
Q

What type of tumour is not surrounded by a capsule

A

Malignant

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6
Q

What do we call molecules that move into the nucleus and switch genes on?

A

Transcriptional factors

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7
Q

What is the purpose of whole-genome shotgun sequencing?

A

Cut the genome into lots of pieces to then later reassemble

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8
Q

If the code has a base added or taken away, this will produce a…

A

Frame shift

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9
Q

If the gene is inaccessible, associated histones have…

A

Decreased acetylation

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10
Q

If the gene is accessible, the cytosine in DNA have…

A

Decreased methylation

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11
Q

What type of gene mutation separates a DNA sequence which then rejoins on a different chromosome?

A

Translocation

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12
Q

Multipotent stem cells can differentiate into _______ type of cell

A

Limited

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13
Q

What process does siRNA inhibit?

A

Translation

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14
Q

What type of gene mutation separates a DNA sequence which then rejoins in the same place but in the reverse order?

A

Inversion

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15
Q

What type of gene mutation removes a nucleotide?

A

Deletion

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16
Q

If the gene is accessible, associated histones have…

A

Increased acetylation

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17
Q

Give an example of where you may find a unipotent stem cell

A

Adult tissue

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18
Q

What is the proteome?

A

All the proteins produced by the genome

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19
Q

If the gene is inaccessible, the cytosine in DNA has…

A

Increased methylation

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20
Q

What type of tumour produces adhesion molecules?

A

Benign

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21
Q

What type of gene mutation replaces one nucleotide with another?

A

Substitution

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22
Q

What effect does oestrogen have on transcription?

A

Activates it

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23
Q

What type of stem cell is an iPS cell produced from?

A

Unipotent

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24
Q

What type of chromatin is tightly packed?

A

Heterochromatin

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25
Q

Hypermethylation can lead to cancer because…

A

It switches off the tumour supressor gene

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26
Q

The epigenome forms a layer around the DNA and histones made up of what?

A

Chemical tags

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27
Q

What type of chromatin is loosely packed?

A

Eurochromatin

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28
Q

What is a SNP?

A

A single base variation in the genome

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29
Q

Give an example of where you may find a pluripotent stem cell

A

Embryo

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30
Q

What type of tumour has systemic effects?

A

Malignant

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31
Q

Give an example of where you may find a totipotent stem cell

A

Zygote/early embryo

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32
Q

What type of gene mutation repeats a base?

A

Duplication

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33
Q

Pluripotent stem cells can differentiate into _______ type of cell

A

Almost any

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34
Q

Unipotent stem cells can differentiate into _______ type of cell

A

Single

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35
Q

What type of tumour rarely reoccurs after treatmen?

A

Benign

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36
Q

What type of gene mutation inserts an extra base in the sequence?

A

Addition

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37
Q

What factors can the epigenome be influenced by?

A
  • Stress
  • Diet
  • Toxis
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38
Q

A mutated proto-oncogene causes the cell to…

A

Rapidly divide

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39
Q

A mutated tumour suppressor gene causes the cell to…

A

Rapidly divide

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40
Q

Does changing the epigenome change the sequence of bases in DNA?

A

No

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41
Q

What chemical acts normally as a transcriptional factor, but increased amounts can lead to tumour formation?

A

Oestrogen

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42
Q

Totipotent stem cells can differentiate into _______ type of cell

A

Any

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43
Q

What are mutations?

A

Changed to the base sequence of DNA

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44
Q

What can cause mutations?

A

Errors during DNA replication

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45
Q

What can increase the rate of mutations?

A

Mutagenic agents

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46
Q

What are the types of mutations that can occur?

A
  • Substitution
  • Deletion
  • Addition
  • Duplication
  • Inversion
  • Translocation
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47
Q

What is a substitution mutation?

A

One or more bases are swapped for another

e.g. ATGCCT becomes ATTCCT

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48
Q

What is a deletion mutation?

A

One or more bases are removed

e.g. ATGCCT becomes ATCCT

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49
Q

What is an addition mutation?

A

One or more bases are added

e.g. ATGCCT becomes ATGACCT

50
Q

What is a duplication mutation?

A

One or more bases are repeated

e.g. ATGCCT becomes ATGCCCCT

51
Q

What is an inversion substitution?

A

A sequence of bases is reversed

e.g. ATGCCT becomes ACCGTT

52
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

53
Q

What can happen if there’s a change in the amino acid sequence (due to mutation)?

A

Change in amino acid sequence of a polypeptide may change final 3D shape of the protein - which might not work properly

e.g. could change the active site

54
Q

How can some mutations cause disease?

A

Genetic disorders - Inherited disorders caused by abnormal genes or chromosomes

e.g. cystic fibrosis

Can also increase the likelihood of developing certain cancers

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

55
Q

What happens if a gamete with a mutation is fertilised?

A

If they contain a mutation for a genetic disease or cancer & is fertilised, the mutation will be present in the foetus formed

These are called hereditary mutations as they’re passed on to offspring

56
Q

Do all mutations affect the order of amino acids and why?

A

No - degenerate nature of the genetic code means that some amino acids are coded for by more than one DNA triplet

e.g. tyrosie - coded for by TAT or TAC in DNA

57
Q

Will a substitution mutation affect the amino acid sequence?

A

Not always, the degenerate nature of genetic code

Some substitutions will still code for the same amino acid if the bases still code for the same triplet - this is called a silent muation

58
Q

Which types of mutations will almost always affect the order of amino acids?

A
  • Additions
  • Duplications
  • Deletions
59
Q

Why do additions, duplications and substitutions almost always change the amino acid sequence?

A

These mutations all change the number if bases in the DNA code

This causes a frameshift in the base triplets that follow so the triplet code is read in a differnt way

60
Q

Which way does a deletion mutation cause a frameshift?

A

To the left

61
Q

Which way does an addition mutation cause a frameshift?

A

To the right

62
Q

What do mutagenic agents do?

A

They increase the rate of mutation

63
Q

How do mutations generally occur?

A

Spontaneuosly

e.g. when DNA is misread during replication

64
Q

Give some examples of mutagenic agents

A
  • Ultraviolet radiation
  • Ionising radiation
  • Some chemicals
  • Some viruses
65
Q

What are the 3 way which mutagenic agents can increase the rate of mutation?

A

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

66
Q

How can 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 base seq. in the new DNA

e.g. 5-bromouracil

67
Q

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

A

Some chemicals can delete/alter bases

e.g. alkylating agents can add an alkyl group to guanine - changes structure so it pairs w thymine (instead of cytosine)

68
Q

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

A

Some types of radiation can change the structure of DNA - causes problems during DNA replication

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

69
Q

What is cancer?

A

Uncontrolled cell growth

70
Q

What are acquired mutations?

A

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

71
Q

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

A
  • Tumour suppressor genes
  • Proto-oncogenes

Mutations in these genes cause cancer

72
Q

What is a tumour?

A

The result of a cell uncontrollably dividing - it is a mass of abnormal cells

Tumours that invade & destroy surrounding tissue are called cancers

73
Q

What happens if an acquired (adulthood) mutation occurs in a control gene?

A

They affect the function of the genes that control the rate of cell division

It can cause uncontrolled cell division

74
Q

What do tumour suppressor genes do?

A

When functioning normally:

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

75
Q

What happens when a tumour suppressor gene mutates?

A

When a mutation occurs:

The protein that stops cell division isn’t produced

The cells divide uncontrollably (rate of division increases) - resulting in a tumour

76
Q

How can tumour suppressor genes be inactivated?

Why is this bad?

A

They can be inactivated if a mutation occurs in the DNA sequence

can allow uncontrolled cell division

77
Q

What is the function of a proto-oncogene?

A

When functioning normally:

They stimulate cell division by producing proteins that make cells divide

78
Q

What happens when a proto-oncogene is mutated?

A

When mutated:

The gene can become overactive - stimulates cells to divide uncontrollably (rate of division increases) resulting in a tumour

Called an oncogene

79
Q

What is the difference in the effects of a mutated tumour suppessor gene and a mutated proto-ongcogene?

A

Mutated tumour suppressor gene –> tumour is not “suppressed”/controlled (rate of division increases)

Mutated proto-oncogene –> divides uncontrollably, rather than at a controlled rate (rate of division increases)

80
Q

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

A

If a mutation occurs in the DNA sequence - the effects fo the proto-oncogene will be increased

81
Q

What is a mutated proto-oncogene called?

A

An oncogene

82
Q

What are the two types of tumours?

A
  • Benign

- Malignant

83
Q

What are malignant tumours like?

A
  • Canerous
  • Grow rapidly & invade and destroy surrounding tissues
  • Cells can break off and spread around the body
84
Q

How can malignant cells travel around the body?

A

They break off the tumour & spread around the body

In the bloodstream and lympatic system

85
Q

What are benign tumours like?

A
  • Not cancerous
  • Slower growing than malignant
  • Often covered in fibrous tissue that stop cells invading other tissues
86
Q

What effects do benign tumours have on the body?

A

They are often harmelss but can cause blockages & put pressure on organs

Some benign tumours can become malignant

87
Q

Are tumour cells the same as normal cells?

A

No - they look different and are functionally different to normal cells

88
Q

How do cancer cells differ to normal cells?

A
  • Have an irregular shape
  • Nucleus larger & darker than normal cells
  • Sometimes cells have more than 1 nucleus
  • Don’t produce proteins needed to function properly
  • Have different antigens on surface
  • Don’t respond to growth regulating processes
  • Divide by mitosis more freq. than normal cells
89
Q

What can abnormal methylation of cancer-related genes cause?

A

Tumour growth

90
Q

What is methylation?

A

It means adding a methyl (-CH3) group onto something

91
Q

Why is methylation of DNA important?

A

It is an important method of regulating gene expression

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

92
Q

When is methylation a good process?

A

When it happens normally - it plays a key role in many bodily processes

93
Q

When does methylation become a bad process?

A

When it happens too much - HYPERMETHYLATION

When it happens too little - HYPOMETHYLATION

It then becomes a problem

94
Q

How can methylation affect cancer?

A

The growth of tumours can be caused by abnormal methylation of certain cancer-related genes

95
Q

What is HYPERMETHYLATION?

A

When methylation occurs too much

96
Q

What is HYPOMETHYLATION?

A

When methylation occurs too little

97
Q

How can HYPERmethylation cause a tumour to form?

A

When tumour suppressor genes are hypermethylated, genes are not transcribed

So proteins they produce to slow cell division aren’t made

Means that cells are able to divide uncontrollably by mitosis & tumours can develop

98
Q

How can increased oestrogen be a risk for some women?

A

Increased exposure to oestrogen over an extended period of time –> thought to increase a woman’s risk for breast cancer

99
Q

How sure are we of how increased oestrogen affects development of breast cancer?

A

The exact reasons why this occurs aren’t fully understood

There are several theories how it can happen

100
Q

What is the theory of how oestrogen can cause some breast cancers?

A

1 - Oestrogen stimulates certain breast cells to divide & replicate - more cell divisions happening = naturally increases chance of mutations & increases chance of cells becoming cancerous

2 - Ability to stimulate division may also mean if cells become cancerous, their rapid replication could be assisted by oestrogen - helps tumours form quickly

3 - Other research shows that oestrogen is able to introduce mutations directly into DNA of certain breast cells, increasing chance of cells becoming cancerous

101
Q

What can totipotent stem cells mature into?

A

Any type of cell

102
Q

Give some examples of specialised cells

A

Liver cells, muscles cells and white blood cells

103
Q

Where do all specialised cells come from?

A

From stem cells

104
Q

What are stem cells?

A

Unspecialised cells that can develop into other types of cell

All multicelluar organisms have some form of stem cell

105
Q

How do stem cells become specialised?

A

They divide to become new cells - they are therefore specialised

106
Q

Where are stem cells found?

A

In the embryo and some adult tissues

107
Q

What happens to stem cells found in an embryo?

A

They become all the specialised cells needed to form a fetus

108
Q

What happens to stem cells found in some adult tissues?

A

They become specialised cells that need to be replaced

e.g. stem cells in the intestines constantly replace intestinal epithelial cells

109
Q

Stem cells that can mature into any type of body cell in an organism are called what?

A

Totipotent cells

110
Q

When are totipotent stem cells present in mammals?

A

They are only present in mammals for the first few cell divisions of an embryo

111
Q

After the first few cell divisions, what do stem cells become like in an embryo and why?

A

Embryonic stem cells become pluripotent

They can still specialise into any cell in the body, but lose the ability to become the cells that make up the placenta

112
Q

What are the two types of stem cells present in adult mammals?

A
  • Multipotent stem cells

- Unipotent stem cells

113
Q

What are multipotent stem cells?

A

They’re able to differentiate into a few different types of cell

e.g. both red & white blood cells can be formed from multipotent stem cells found in bone marrow

114
Q

What are unipotent stem cells?

A

They can only differentiate into one type of cell

e.g. there’s a type of unipotent cell that can only divide to produce epiderman skin cells, that make up the outer layer of your skin

115
Q

Why do stem cells become specialised into cells with different functions?

A

Because different genes are expressed

Stem cells all contain the same genes - but when they develop, not all of the genes are trascribed/translated

116
Q

What are the factors that increase the chance of cancer called?

A

Risk factors

117
Q

What are the 2 risk factors?

A
  • Genetic

- Environmental

118
Q

What are examples of environmental factors that increase risk of cancer?

A
  • Exposure to radiation
  • Smoking
  • Alcohol
  • High fat diet
119
Q

What is the process of a cell becoming specialised?

A

1 - Stem cells all contain same genes - in development not all are transcribed/translated

2 - Under right conditions some genes are expressed & others are switched off

3 - mRNA only transcribed from specific genes

4 - The mRNA from these genes is then translated into proteins

5 - These proteins modify the cell – they determine cell structure & crontrol cell processes (including expression of more genes)

6 - Changes to cell produced by these proteins cause cell to become specialised - changes are difficult to reverse so cell stays specialised

120
Q

Why do cells stay specialised (they cannot become stem cells again)?

A

The changes that have been made to the cell (by the proteins) are too difficult to reverse so the cell stays specialised

121
Q

Where are the stem cells that form red blood cells found?

A

The type of stem cell that forms RBC is found in bone marrow

122
Q

How do red blood cells become specialised from a stem cell?

A

The stem cell produces a new cell in which the genes for haemoglobin production are expressed

Other genes such as those involved in removing the nucleus are expressed too

Many other genes are not expresssed (switched off) - results in specialised RBC

(RBC has lots of haemoglobin & no nucleus)

Biology A-level (20 decks)

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