8A Mutations and Gene Expression Flashcards
1
Q
How can hypomethylation lead to cancer?
A
It switches on the oncogene
2
Q
Which type of tumourc an metastatise?
A
Malignant
3
Q
Give an example of where you may find a multipotent stem cell
A
Bone marrow
4
Q
What is the science of collecting and analysing complex biological data called?
A
Bioinformatics
5
Q
What type of tumour is not surrounded by a capsule
A
Malignant
6
Q
What do we call molecules that move into the nucleus and switch genes on?
A
Transcriptional factors
7
Q
What is the purpose of whole-genome shotgun sequencing?
A
Cut the genome into lots of pieces to then later reassemble
8
Q
If the code has a base added or taken away, this will produce a…
A
Frame shift
9
Q
If the gene is inaccessible, associated histones have…
A
Decreased acetylation
10
Q
If the gene is accessible, the cytosine in DNA have…
A
Decreased methylation
11
Q
What type of gene mutation separates a DNA sequence which then rejoins on a different chromosome?
A
Translocation
12
Q
Multipotent stem cells can differentiate into _______ type of cell
A
Limited
13
Q
What process does siRNA inhibit?
A
Translation
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
15
Q
What type of gene mutation removes a nucleotide?
A
Deletion
16
Q
If the gene is accessible, associated histones have…
A
Increased acetylation
17
Q
Give an example of where you may find a unipotent stem cell
A
Adult tissue
18
Q
What is the proteome?
A
All the proteins produced by the genome
19
Q
If the gene is inaccessible, the cytosine in DNA has…
A
Increased methylation
20
Q
What type of tumour produces adhesion molecules?
A
Benign
21
Q
What type of gene mutation replaces one nucleotide with another?
A
Substitution
22
Q
What effect does oestrogen have on transcription?
A
Activates it
23
Q
What type of stem cell is an iPS cell produced from?
A
Unipotent
24
Q
What type of chromatin is tightly packed?
A
Heterochromatin
25
Hypermethylation can lead to cancer because...
It switches off the tumour supressor gene
26
The epigenome forms a layer around the DNA and histones made up of what?
Chemical tags
27
What type of chromatin is loosely packed?
Eurochromatin
28
What is a SNP?
A single base variation in the genome
29
Give an example of where you may find a pluripotent stem cell
Embryo
30
What type of tumour has systemic effects?
Malignant
31
Give an example of where you may find a totipotent stem cell
Zygote/early embryo
32
What type of gene mutation repeats a base?
Duplication
33
Pluripotent stem cells can differentiate into _______ type of cell
Almost any
34
Unipotent stem cells can differentiate into _______ type of cell
Single
35
What type of tumour rarely reoccurs after treatmen?
Benign
36
What type of gene mutation inserts an extra base in the sequence?
Addition
37
What factors can the epigenome be influenced by?
- Stress
- Diet
- Toxis
38
A mutated proto-oncogene causes the cell to...
Rapidly divide
39
A mutated tumour suppressor gene causes the cell to...
Rapidly divide
40
Does changing the epigenome change the sequence of bases in DNA?
No
41
What chemical acts normally as a transcriptional factor, but increased amounts can lead to tumour formation?
Oestrogen
42
Totipotent stem cells can differentiate into _______ type of cell
Any
43
What are mutations?
Changed to the base sequence of DNA
44
What can cause mutations?
Errors during DNA replication
45
What can increase the rate of mutations?
Mutagenic agents
46
What are the types of mutations that can occur?
- Substitution
- Deletion
- Addition
- Duplication
- Inversion
- Translocation
47
What is a substitution mutation?
One or more bases are swapped for another
e.g. ATGCCT becomes ATTCCT
48
What is a deletion mutation?
One or more bases are removed
e.g. ATGCCT becomes ATCCT
49
What is an addition mutation?
One or more bases are added
e.g. ATGCCT becomes ATGACCT
50
What is a duplication mutation?
One or more bases are repeated
e.g. ATGCCT becomes ATGCCCCT
51
What is an inversion substitution?
A sequence of bases is reversed
e.g. ATGCCT becomes ACCGTT
52
What is a translocation mutation?
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
What can happen if there’s a change in the amino acid sequence (due to mutation)?
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
How can some mutations cause disease?
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
What happens if a gamete with a mutation is fertilised?
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
Do all mutations affect the order of amino acids and why?
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
Will a substitution mutation affect the amino acid sequence?
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
Which types of mutations will almost always affect the order of amino acids?
- Additions
- Duplications
- Deletions
59
Why do additions, duplications and substitutions almost always change the amino acid sequence?
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
Which way does a deletion mutation cause a frameshift?
To the left
61
Which way does an addition mutation cause a frameshift?
To the right
62
What do mutagenic agents do?
They increase the rate of mutation
63
How do mutations generally occur?
Spontaneuosly
e.g. when DNA is misread during replication
64
Give some examples of mutagenic agents
- Ultraviolet radiation
- Ionising radiation
- Some chemicals
- Some viruses
65
What are the 3 way which mutagenic agents can increase the rate of mutation?
1 - Acting as a base
2 - Altering bases
3 - Changing the structure of DNA
66
How can mutagenic agents acting as a base increase the rate of mutation?
Chemicals called base analogs can substitute for a base during DNA replication - changing base seq. in the new DNA
e.g. 5-bromouracil
67
How can mutagenic agents altering bases increase the rate of mutation?
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
How can mutagenic agents changing the structure of DNA increase the rate of mutation?
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
What is cancer?
Uncontrolled cell growth
70
What are acquired mutations?
Mutations that occur in individual cells after fertilisation (e.g. adulthood)
71
What are the two types of gene that control cell division?
- Tumour suppressor genes
- Proto-oncogenes
Mutations in these genes cause cancer
72
What is a tumour?
The result of a cell uncontrollably dividing - it is a mass of abnormal cells
Tumours that invade & destroy surrounding tissue are called cancers
73
What happens if an acquired (adulthood) mutation occurs in a control gene?
They affect the function of the genes that control the rate of cell division
It can cause uncontrolled cell division
74
What do tumour suppressor genes do?
When functioning normally:
They slow cell division by producing proteins that stop cells dividing/ cause them to self-destruct (apoptosis)
75
What happens when a tumour suppressor gene mutates?
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
How can tumour suppressor genes be inactivated?
Why is this bad?
They can be inactivated if a mutation occurs in the DNA sequence
can allow uncontrolled cell division
77
What is the function of a proto-oncogene?
When functioning normally:
They stimulate cell division by producing proteins that make cells divide
78
What happens when a proto-oncogene is mutated?
When mutated:
The gene can become overactive - stimulates cells to divide uncontrollably (rate of division increases) resulting in a tumour
Called an oncogene
79
What is the difference in the effects of a mutated tumour suppessor gene and a mutated proto-ongcogene?
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
How can the effects of a proto-oncogene be increased?
If a mutation occurs in the DNA sequence - the effects fo the proto-oncogene will be increased
81
What is a mutated proto-oncogene called?
An oncogene
82
What are the two types of tumours?
- Benign
| - Malignant
83
What are malignant tumours like?
- Canerous
- Grow rapidly & invade and destroy surrounding tissues
- Cells can break off and spread around the body
84
How can malignant cells travel around the body?
They break off the tumour & spread around the body
In the bloodstream and lympatic system
85
What are benign tumours like?
- Not cancerous
- Slower growing than malignant
- Often covered in fibrous tissue that stop cells invading other tissues
86
What effects do benign tumours have on the body?
They are often harmelss but can cause blockages & put pressure on organs
Some benign tumours can become malignant
87
Are tumour cells the same as normal cells?
No - they look different and are functionally different to normal cells
88
How do cancer cells differ to normal cells?
- 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
What can abnormal methylation of cancer-related genes cause?
Tumour growth
90
What is methylation?
It means adding a methyl (-CH3) group onto something
91
Why is methylation of DNA important?
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
When is methylation a good process?
When it happens normally - it plays a key role in many bodily processes
93
When does methylation become a bad process?
When it happens too much - HYPERMETHYLATION
When it happens too little - HYPOMETHYLATION
It then becomes a problem
94
How can methylation affect cancer?
The growth of tumours can be caused by abnormal methylation of certain cancer-related genes
95
What is HYPERMETHYLATION?
When methylation occurs too much
96
What is HYPOMETHYLATION?
When methylation occurs too little
97
How can HYPERmethylation cause a tumour to form?
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
How can increased oestrogen be a risk for some women?
Increased exposure to oestrogen over an extended period of time --> thought to increase a woman's risk for breast cancer
99
How sure are we of how increased oestrogen affects development of breast cancer?
The exact reasons why this occurs aren't fully understood
There are several theories how it can happen
100
What is the theory of how oestrogen can cause some breast cancers?
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
What can totipotent stem cells mature into?
Any type of cell
102
Give some examples of specialised cells
Liver cells, muscles cells and white blood cells
103
Where do all specialised cells come from?
From stem cells
104
What are stem cells?
Unspecialised cells that can develop into other types of cell
All multicelluar organisms have some form of stem cell
105
How do stem cells become specialised?
They divide to become new cells - they are therefore specialised
106
Where are stem cells found?
In the embryo and some adult tissues
107
What happens to stem cells found in an embryo?
They become all the specialised cells needed to form a fetus
108
What happens to stem cells found in some adult tissues?
They become specialised cells that need to be replaced
e.g. stem cells in the intestines constantly replace intestinal epithelial cells
109
Stem cells that can mature into any type of body cell in an organism are called what?
Totipotent cells
110
When are totipotent stem cells present in mammals?
They are only present in mammals for the first few cell divisions of an embryo
111
After the first few cell divisions, what do stem cells become like in an embryo and why?
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
What are the two types of stem cells present in adult mammals?
- Multipotent stem cells
| - Unipotent stem cells
113
What are multipotent stem cells?
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
What are unipotent stem cells?
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
Why do stem cells become specialised into cells with different functions?
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
What are the factors that increase the chance of cancer called?
Risk factors
117
What are the 2 risk factors?
- Genetic
| - Environmental
118
What are examples of environmental factors that increase risk of cancer?
- Exposure to radiation
- Smoking
- Alcohol
- High fat diet
119
What is the process of a cell becoming specialised?
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
Why do cells stay specialised (they cannot become stem cells again)?
The changes that have been made to the cell (by the proteins) are too difficult to reverse so the cell stays specialised
121
Where are the stem cells that form red blood cells found?
The type of stem cell that forms RBC is found in bone marrow
122
How do red blood cells become specialised from a stem cell?
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)
