Control Of Gene Expression Flashcards
1
Q
What is a mutation?
A
A change to the nucleotide sequence of DNA
2
Q
When do spontaneous mutations happen?
A
During DNA replication (interphase)
3
Q
What is a mutagenic agent?
A
Something that increases the rate of mutations above normal
4
Q
What is a base analog?
A
Something that can substitute for a normal nucleotide base
5
Q
What type of mutation does a base analog cause?
A
A substitution mutation
6
Q
What does radiation do to DNA?
A
Changes the structure of it
7
Q
What are the types of mutations?
A
- Substitution - Addition- Deletion- Inversion- Duplication- Translocation
8
Q
What happens in a substitution mutation?
A
- One base is swapped for another
9
Q
What can a substitution mutation do to the amino acids translated for?
A
- Can have no effect because DNA is degenerate - Can change one amino acid
10
Q
What can cause a substitution mutation?
A
Some chemicals are able to react with DNA and change its structure
11
Q
What happens in an addition mutation?
A
An extra base is added
12
Q
What happens in a deletion mutation?
A
A base is removed
13
Q
What can addition and deletion mutations cause?
A
A frame shift
14
Q
What happens if a frame shift occurs?
A
All the following DNA triplets will be affected
15
Q
What happens in an inversion mutation?
A
A sequence of DNA is reversed
16
Q
What can an inversion mutation cause?
A
- No change (palindromic)- Change to one or a few amino acids- No frame shift (nothing added or removed)
17
Q
What is a duplication mutation?
A
One or more bases are repeated
18
Q
What can a duplication mutation cause?
A
A frame shift
19
Q
What is translocation?
A
When a sequence of DNA is removed from one part of the genome and moved to another part of the genome (can be the same or a different chromosome)
20
Q
What is a mutation?
A
A change to the base sequence of DNA
21
Q
Why can a mutation result in no change to the amino acid sequence?
A
- Amino acids are coded for by more than one triplet of DNA- DNA is degenerate
22
Q
What happens if a mutation results in a change to one DNA triplet?
A
- Changes the transcription and translation - Different amino acid made- Changes the primary structure of the protein- Changes the hydrogen/ionic bonding- Changes the tertiary structure of the protein
23
Q
What effect will a frame shift have on the resultant protein?
A
- Changes the sequence of all the following triplets- Changes all the following amino acids- Changes the primary structure- Changes the hydrogen/ionic bonding- Changes the tertiary structure
24
Q
What mutations can result in a frame shift?
A
- Additions- Deletion- Duplication
25
What are stem cells?
Cells that can divide and differentiate to become different types of cell and can divide for the organisms whole life
26
What are totipotent stem cells?
- Stem cells that can differentiate into any type of specialised cell- Can for placental cells
27
Where are totipotent stem cells found?
Vey early mammalian embryos
28
What are pluripotent stem cells?
- Stem cells that can differentiate into many types of specialised cell- Cant make placental cells
29
Where are pluripotent stem cells found?
Adult and embryo cells
30
What are multipotent stem cells?
Stem cells that can differentiate into a few types of specialised cell
31
What is an example of multipotent stem cells?
Bone marrow can differentiate into red blood cells or white blood cells
32
What are unipotent stem cells?
Stem cells that can differentiate into one type of specialised cell
33
What is an example of unipotent stem cells?
Heart unipotent cells can make cardiomycytes only
34
How does cell specialisation happen?
- All cells contain 100% of an organisms DNA- Conditions within cells control which genes are expressed (transcribed and translated) into proteins- Transcription factors change the internal environment of the cell and affect the expression of other genes- Cells become specialised
35
What happens once a cell becomes specialised?
It cannot be reversed
36
What are IPS cells?
Induced pluripotent stem cells made by treating unipotent stem cells with transcription factors that make them become pluripotent
37
How are IPS cells made?
- Modified virus as a vector- Virus inserts transcription factor genes from pluripotent cells into the DNA of unipotent stem cells- Transcription factors are expressed
38
How are embryonic stem cells obtained?
- Embryos made in a lab by IVF- Pluripotent stem cells removed after a few days- Embryo destroyed
39
How are adult stem cells obtained?
Taken from adults in an operation e.g. the removal of bone marrow
40
Why are adult stem cells less useful for medicine
Adult stem cells are multipotent therefore less useful for medicine as they cannot for every type of cell
41
What can stem cells do?
Differentiate to form any type of specialised cell
42
What can stem cells . e used for?
Replacing faulty or damaged genes
43
What does bone marrow contain?
Multipotent stem cells that can differentiate into red and white blood cells
44
What can you do if someone has faulty bone marrow?
Replace their bone marrow with a donors bone marrow which will form new healthy cells
45
Why would someone have faulty bone marrow?
Genetic disorder or leukemia
46
How can stem cells be used to grow new organs?
- IPS cells used- No donor needed- IPS organs will have the same antibodies preventing rejection
47
What are the advantages of stem cells?
- Save lives- Improve quality of life- Prevent suffering
48
What are the ethical issues surrounding stem cells?
- Stem cells are taken from IVF embryos which could develop into a fetus if implanted- Some people believe from fertilisation a zygote has the right to live- Use unfertilised eggs that are triggered to divide
49
What is a transcription factor?
A protein that controls the rate of protein synthesis by switching some genes on and some genes off
50
What is a promoter region?
Short sequence of DNA at the start of a gene (the bit that RNA polymerase/ DNA polymerase attaches to)
51
What does an activator do?
Help RNA/DNA polymerase bind to DNA
52
What does a repressor do?
Prevent RNA/DNA polymerase bind to DNA
53
How do activators and repressors work?
- Transcription factor moves from the cytoplasm into the nucleus- Binds to the promoter regions- Controls whether gene is or isn't transcribed
54
What is an example of controlling transcription factors?
- Oestrogen is a steroid hormone- If it is present it will bind to an oestrogen receptor to form an oestrogen-oestrogen receptor complex
55
How can transcription factors be turned on or off?
By second messengers e.g. cAMP
56
What do tumour suppressor genes and proto-oncogenes do?
Control the rate of mitosis and therefore the expression of genes
57
What is cancer?
Uncontrolled cell division
58
What do proto-oncogenes do?
Make proteins that increase the rate of mitosis
59
What is an oncogene?
A mutated proto-oncogene
60
What can happen to oncogenes?
They can be over expressed
61
What do tumour suppressor genes do?
Make proteins that slow down the rate of mitosis or speed up the rate of apoptosis
62
What happens if there is a mutation to a tumour suppressor gene or a proto-oncogene?
The resultant synthesised protein may be non-functional that may cause uncontrolled cell division
63
What is epigenetics?
Changes to gene expression caused by environmental factors (without changing the base sequence of DNA)
64
What does epigenetics do?
- Controls gene expression by preventing transcription- Can be inherited between generations- Helps organisms respond to environmental factors
65
What is an example of epigenetics?
If pregnant mice are exposed to famine their off spring will be better adapted to low nutrients
66
What is the methylation of DNA?
- More Methylation Terminates Transcription- Methyl groups can attach to DNA at CpG sites- Methylated CpG sites prevent transcription enzymes attaching- Methyl groups can be removed by enzymes
67
What is the acetylation of DNA?
- Less Acetylation Terminates Transcription- Acetyl groups force histones to be more spread apart - DNA is less coiled- Allows transcription enzymes to attach- Enzymes can remove acetyl groups to prevent transcription
68
What can SiRNA and MicroRNA do?
Control gene expression by preventing translation
69
What is SiRNA?
Small interfering RNA
70
How does SiRNA work?
1 - Short double stranded RNA2 - Combines with proteins to form an SiRNA - protein complex 3 - SiRNA - protein complex single stranded 4 - SiRNA has a complimentary base sequence to target mRNA 5 - SiRNA - protein complex breaks down the mRNA into pieces 6 - Prevents translation7 - mRNA pieces are recycled
71
What does MicroRNA do?
1 - MicroRNA combines with a protein to form a MicroRNA - protein complex 2 - MicroRNA - protein complex binds to mRNA by complimentary base pairing3 - Prevents translation by blocking the ribosome from attaching4 - mRNA can be stored for later or recycled
72
How are the ways MicroRNA and SiRNA different?
MicroRNA is less specific that SiRNA and MicroRNA can work on multiple mRNA strands
73
How can gene expression (transcription) be controlled?
Methylating DNA
74
In what two ways can tumours be effected by methylation?
Tumours can be hypermethylated or hypomethylated
75
If a tumour is hypermethylated, which gene is said to have mutated?
Tumour supressor gene
76
If a tumour is hypomethylated, which gene is said to have mutated?
Proto-oncogene
77
What are the two types of tumour?
Benign and malignant
78
What is a benign tumour?
- Enclosed in a membrane- Slow growing- Harmless- Can become malignant if the membrane ruptures
79
What is a malignant tumour?
- Fast growing- Destroys tissue- Can easily break apart and spread in the blood/lymph
80
How can oestrogen cause breast cancer?
- Oestrogen can bind to a protein to form the oestrogen - oestrogen receptor complex- Increases rate of cell division- Increases rate of mutations- Can lead to cancer
81
How can tumours be identified?
- Mitosis (more cells dividing)- Nuclei (large, odd shapes, multiple)- Cell shape (irregular)- Function (loss of normal function)- Arrangement (disorganised)
82
What is the genome?
The complete set of genetic material (genes and non coding DNA) that an organism has
83
What is the proteome?
The complete set of proteins that an organism can make
84
What is a current sequencing project?
Human genome project (sequence a whole human genome)
85
What is the current sequencing method used to sequence the human genome?
High thouroughput pyrofrequency- Faster- Cheaper- Automated
86
Why can we predict the amino acid sequence of simple prokaryotes but not large eukaryotes?
Simple organisms are made up of very few regulating genes and contain little non-coding DNA whereas in complex organisms we have regulating genes, the ability to turn genes on/off, lots of non-coding DNA so it is hard to determine our proteins from our DNA
87
What are the uses of genome projects?
- Understanding evolutionary relationships (phylogeny)- Medicine
88
How are genome projects useful in medicine?
Understand the antigens to develop new vaccines
