Topic 8 - Mutations and Gene Expression Flashcards
1
Q
when does mutation occur
A
dna replication
2
Q
what is a duplication mutation
A
one or more bases are repeated
always causes a frame shift
3
Q
what is an inversion mutation
A
a sequence of bases is reversed
4
Q
what is translocation mutation
A
- a sequence of bases is moved from one location in the genome to another
- could be within a same chromosome or a different one
5
Q
how can mutagenic agents increase the rate of mutations
A
- acting as a base - chemicals callled base analogs can substitute for a base during dna replication, changing the sequence
- altering bases - some chemicals can delete or alter bases
- changing th structure of DNA - Some types of radiation can change the structure of DNA which causes problems during replication
6
Q
what are stem cells
A
undifferentiated cells with the potential to differentiate into a variety of the specialised cell types of the organism
7
Q
where are stem cells found in humans
A
embryo
stem cells
8
Q
what are totipotent stem cells
A
- stem cells that can differentiate into any type of body cell including the placenta
- they are only present in the first few cell divisions of an embryo
9
Q
what are pluripotent stem cells
A
- stem cells that can specialise into any cell in the body but cannot make up the placenta
10
Q
what are unipotent stem cells
A
- stem cells that can only differentiate into one type of cell
11
Q
what are multipotent stem cells
A
- stem cells that can differentiate into a few different types of cells
12
Q
how do stem cells become specialised
A
- mRNA is only transcribed for specific genes
- the mRNA is then translated into proteins
- These proteins modify the cell - they determine the cell structure and control cell processes
- changes to the cell produced by the proteins cause the cell to become specialised
- these changes are difficult to reverse
13
Q
what is an example of a unipotent stem cells
A
cardiomyocytes
14
Q
what are cardiomyocytes
A
- heart muscle cells that make up the tissue in our hearts
- some scientists think that old or damaged cardiomyocytes can be replaced by new cardiomyocytes derived from a small supply of unipotent stem cells in the heart
15
Q
how are stem cells used to treat disease
A
- bone marrow transplant
- stem cells divide and specialise into healthy cells
16
Q
what type of stem cells are in bone marrow
A
multipotent
17
Q
how are embryonic stem cells extracted
A
- embryos created in a lab using IVF - egg cell is fertilised outside thw womb
- once the embryos are 4-5 days old stem cells are removed from them and the rest of the embryo is destroyed
- embryonic stem cells can divide an unlimited number of times and develop into all types of body cells - pluripotent
18
Q
what are induced pluripotent stem cells
A
- reprogramming specialised adult body cells so they become pluripotent
- the adult cells are made to express a series of transcription factors that are associated with pluripotent stem cells
- one of the ways that these can be introduced is by infecting them with a modified virus
19
Q
why do organisms carry the same genes but the structure and function of cells varies
A
- different genes are expressed
- different proteins are made
- these proteins modify the cell
- they determine cell processes and structure
20
Q
what is transcription controlled by
A
transcription factors
21
Q
how do activator transcription factors work
A
- in eukaryotes, transcription factors move from the cytoplasm to the nucleus
- in the nucelus they bind to specific DNA sites near the start of their target genes - the genes they control the expression of
- some transcription factors called activators stimulate or increase the transcription, e.g. help RNA polymerase bind to the start of the target genes
22
Q
how do repressor transcription factors work
A
- decrease the rate of transription
- they bind to the start of the target gene
- preventing RNA polymerase from binding, stopping transcription
23
Q
how does oestrogen initiate transcription of a target cell
A
- oestrogen is a steroid hormone that binds to a oestrogen receptor forming an oestrogen-oestrogen receptor complex
- the complex moves from the cytoplasm into the nucleus where it binds to specific DNA sites near the start of the target gene
- the complex can act as an activator of transcription
24
Q
what is RNA interference
A
- inhibits the translation of mRNA
- Molecules involved are called siRNA (small interfering RNA) and miRNA (microRNA)
25
what is the epigenome
* histones are covered in chemical 'tags'
* tags are the epigenome
* they determine the shape of the histone-DNA complex
26
what is epigenetics
* heritable changes in gene funcion
* without changes to the base sequence of DNA
* these changes are caused by changes in the environment that inhibit transcription
27
what do histones do
help the DNA condense into chromatids
28
what is one way of epigenetic control with methyl
* increased mathylation of DNA
* a methyl group is attched to the DNA coding for a gene
* the group always attaches where the cytosine and gumanine are next to each other
* increased methylation changes the DNA structure so the histones wrap tightly around tha DNA
* RNA polymerase cannot bind to the promoter for transcription
29
what is one method of epigenetic control with acetyl
* decreased acetylation of histones
* when an acetyl group is removed there is an increased positive charge on the histones
* this makes them more strongly atatched to the phosphate in the DNA nucleotide
* increases DNA and histine attraction
* RNA polymerase cannot bind to the promoter
* transcription cannot occur
30
how could drugs be used to treat disease caused by epigenetics
* changes are reversible, making thwm a good target for new drugs
* these drugs counteract the changes causes by the disease
* e.g. a drug to stop DNA methylation
* **problems** - changes take place in alot of cells so drugs need to be specific
31
what is a tumour
* a mass of abnormal cells due to uncontrollable cell division
32
what are malignant tumours
* cancerous
* grow rapidly and invade and destroy surrounding tissues
* cells can break off and spread to other parts of the body in the blood stream or lymphatic system
33
what are benign tumours
* not cancerous
* grow slower then malignant tumours and are often covered in fibrous tissue that stops them from invading other tissues
* can cause blockages and put pressure on organs
* can become malignant
34
what are the 2 types of genes that control cell division
* proto oncogens
* tumour supressors
35
what happens if tumour suppressors are inactive
* proteins involved in cell death are not produced
* causes uncontrolled cell division
* resulting in a tumour
36
what happens if proto oncogens are increased
* the gene will become over active
* producting more proteins to make cells divide
* causes uncontrollable cell division
* resulting in a tumour
37
how are tumour cells different to normal cells
* irregular shape
* dont produce all proteins needed
* different antigens
* divide more frequently
38
how does abnormal methylation of tumour supressors cause tumour growth
* when a tumour suppressor gene is methylated too much the histones wrap tighly around it so RNA polymerase cannot bind to the promoter so the gene is not transcribed
* it cannot produce its proteins which means less cell death
* more uncontrollable cell division
39
how does decrease methylation of proto oncogens cause tumours
* increases production of protein which encourages cell division
* uncontrollable cell division
40
how does increased oestrogen contribute to breast cancer
* The cancer cells within the tumours have oestrogen receptors
* oestrogen binds to the receptors
* the complex moves from the cytoplasm to the nucleus and binds to the promoter of the gene
* the gene is transcribed
