8- Mutations And Genes Flashcards
What is a mutation
Any change to the base sequence of dna
When can mutations occur
Error during DNA replication
What can increase rate of mutations
Mutagenic agents
What are the 6 types of mutations
Substitution
Deletion
Addition
Duplication
Inversion
Translocation
Substitution mutation
One of more bases are swapped for another
Deletion mutation
One or more bases are removed
Addition mutation
One of more bases are added
Duplication mutation
One or more base are repeated
Inversion mutation
A sequence of bases is revers3d
Translocation mutation
A sequence of bases is moved form one location in. The genome to another
This could be movement within the same chromosome or movement to a differnt chromosome
What determines the polypeptide
The order of dna bases in a gene
Determined the sequence of amino acids
How does mutation in a gene. Effect a polypeptide
Sequence of amino acids change so polypeptide changes
Why might a mutation in an enzyme stop it working
A change in amino acid sequence may change the final 3D shape of the protein . The active site may change so substrates are no longer complementary so can’t bind
Explain how some mutations can cause genetic disorders
Inherited disorders caused by abnormal genes or chromosomes
Some mutations can increase the likelihood of developing certain cancers
What is a hereditary mutation
If a gamete containing a mutation for a genetic disorder or a type of cancer is fertilised it will be present in the new fetus formed
Why do not all mutation affect the order of amino acids
The degenerate nature of genetic code means that some amino acid are coded for by more than one dna triplet .
This means that not all types of mutation will always result in a change of amino acid sequences of the polypeptide
Eg. Some substitution will still code for the same amino acid and some inversion
If a mutation doesn’t cause a change in amino acid order what is it called
A silent mutation
What mutations cause a frame shift
Addition , deletion , duplication
Why do Addition duplicated and deletions almost always change amino acid sequence
they change the number of bases present
This causes a frame shift
Base triplets that follow on from the mutation are said to be …….. of the mutation
Downstream
When do mutations occur
Spontaneously
Eg. When dna is misread during replication
Examples of mutagenic agents
Ultra violet radiation
Ionising radiation
Some chemicals
Some viruses
What 3 ways can mutagenic agents increase rate of mutations
Acting as a base
Altering vases
Changing the structure of dna
What 3 ways can mutagenic agents increase rate of mutations
Acting as a base
Eg,
Chemicals called base analogs can substitute for a base during dna replication . Changing the base sequence in the new DNA
5-bromouracil is a base analog that can substitute for thymine. It can pair with guanine causing a substitution mutation in the new dna
What 3 ways can mutagenic agents increase rate of mutations
Altering bases
Eg,
Some chemicals can delete or alter bases
Eg, Alkylating agents can add an alkyl group to guanine which changes the structure so that is pairs with thymine
What 3 ways can mutagenic agents increase rate of mutations
Changing the structure of dna
Eg
Some types of radiation can change the structure of dna which.
Causes problems during dna replication
Eg, uv radiation can cause adjacent thymine bases to pair up togetehr
Mutations that occur in individual cells after fertilisation are called….
Acquired mutations
If an acquired mutation occurs in genes that control rate of cell division ( by mitosis) what can happen
Uncontrolled cell division
If a cell divides uncontrollably the results is a ….
Tumour
What is a tumour
A mass of abnormal cells
When are tumours cancer
Theme they invade and destroy surrounding tissue
What are the two types of gene that control cell division
Tumour suppressor genes
Proto-oncogenes
Mutations in tumour suppressor genes and proto-oncogenes cause ….
Cancer
What happens if a mutation occurs in a tumour suppressor gene
The gene can be inactivated
When functioning normally, tumour suppressor genes slow cell division by product of proteins that stop cell dividing or cause them to self distruct( apoptosis ;
If a mutation occurs in a tumour suppressor gene, the protein isn’t produced. The cells divide uncontrollably , resulting in a tumour
What happens if a mutation occurs in a proto-oncogene
The effect of the gene can be increased if a mutation occurs in the dna sequence
When functioning normally , proto-oncogenes stimulate cell division by producing proteins that make cells divide
If a mutation occurs in a proto-oncogene , the gene can become overactive. This stimulated the cells to divide uncontrollably resulting in a tumour
What is a mutated proto-oncogene called
Oncogene
What are the two types of tumours
Malignant
Benign
What is a malignant tumour
Cancers
They usually grow rapidly and invade and destroy surrounding tissues. Cells can break off the rumours and spread to other parts of the body in the blood stream or lymphatic system
What is a benign tumour
Non cancerous . They usually grow slower than malignant tumours, and a tee oftern cover in fibourous tissues that stop cells invading other tissues. Benign tumour are oftern harmless , but they can cause bloackages and put pressure on organs
Can benign tumours become malignant
Yes
How might tumour cells differ to normal cells
1) irregular shape
2)nucleus larger an darker, sometimes the cells have more than one nucleus
3) they don’t produce all proteins needed ot function correctly
4) they have differnt antigens on their surface
5: they don’t respond to growth regulating processes
6) they divide more frequently than normal cells
What is methylation
Adding a methyl (CH3) group onto something
What is methylating of DNA an important method of
Regulating gene expression - it can control whether or not a gene is transcribed and translated
When methylation is happening normally, what does it play a key role in
Many processes in the body
WhT is it called if methylation occurs to much
Hypermethylation
What is it called when methylation occurs to little
Hypomethylation
How can tumour growth be caused by hypermethylation
When tumour suppressor genes are hypermethylated, the genes are not transcribed - so the proteins they produce to slow down cell divison arnt made. Thus means that cells are able to divide uncontrollably by mitosis and tumours can develope
How can tumour growth be caused by hypomethylation
Hypomethylation of proto-oncogene chauses them to act as oncogenes - increasing the production of the proteins that encourages cell divison , this stimulated cells to divide uncontrollably which causes the formation of tumours
What can increased exposure to oestrogen over an extended period of time cause
Increase risk of developing breast cancer
What can u creased exposure to oestrogen be due to
starting menstruation earlier then usual t or menopause later
What are the 3 theory’s of how oestrogen can contribute to the development of some breast cancers
1) oestrogen can stimulate certain breast cells to divide and replicate. The facts that more cell divison are taking place naturally increase the chances of mutations occurring m and so increases the chance of cells becoming cancerous
2) This ability to stimulate division could also mean that if cells do become cancerous, their rapid replication could be further assisted by ostrogen, helping tumours to form quickly.
3) Other research suggests that ostrogen is actually able to introduce mutations directly into the DNA of certain breast cells, again increasing the chance of these cells becoming cancerous.
Where do all specialised cell come form
Stem cells
What are stem cells
Unspecialised cells that can develop into other types of cell
They divide to become new cells which then become specialised
T or f
All multicellular organism have some form of stem cells
T
Where are stem cells found
Embryo
Some adult tissue
What are stem cells found in the embryos for
Become all the specialised cells needed to form the fetus
What are stem cells found in some adult tissue for
they become specialised cells that need to be replaced
what is a totipotent cell
stem cells that can mature into any time of body cell in an organism
when are totipotent stem cells present in mammals
In the first few cell divisions of an embryo
After totipotent stem cells, the embryonic stem cells become …..
Pluripotent
What are pluripotent cells
They can still specialise into any cell in the body, but lose the ability to become the cells that make up the placenta
What 2 types of stem cells are present in adult mammals
Multi potent
Unipotent
What are multipotent stem cells
These are able to differentiate into a few differnt types of cells
Eg, red and white blood cells can be formed form them found in bone marrow
What are unipotent stem cells
these can only differentiate into one type of cell.