8.1 Mutation Flashcards
What are the 6 types of mutations?
- Addition
- Deletion
- Substitution
- Inversion
- Duplication
- Translocation
Describe addition mutations
Addition mutations are where one or more bases are added to the DNA sequence.
Describe deletion mutations
Deletion mutations are where one or more bases are removed from the DNA sequence.
Describe substitution mutations
Substitution mutations are where bases are removed and then replaced in the DNA sequence.
Describe inversion mutations
Inversion mutations are where the order of bases in the DNA sequence are reversed.
Describe duplication mutations
Duplication mutations are where bases are repeated in the DNA sequence.
Describe translocation mutations
Translocation mutations are where a section of the DNA sequence is moved to another section of the DNA sequence.
Translocation can be within and across chromosomes.
How do mutations affect the proteins that an organism produces?
Mutations give rise to a change in the base sequence in DNA.
This could alter the amino acids that the DNA encodes.
If the amino acids in a protein are changed, the 3D structure of the protein may break down as bonds between R groups of amino acids can differ.
Explain how the DNA code being degenerate means that some mutations have no effect
Some amino acids are encoded by more than one codon.
The fact that DNA is degenerate means that a mutation in the base sequence does not necessarily affect the protein.
If one base is substituted for another base, (e.g. CAA → CAG), the mutated codon may still encode the same amino acid (e.g. both encode glutamine).
Which types of mutations cause frame shifts?
- Addition
- Deletion
- Duplication
What are the two causes of mutations?
-DNA replication - There can be be errors in the replication process causing mutations.
-Mutagenic agents - Can increase the rate at which mutations occur e.g. UV radiation, smoking etc.
What is a hereditary mutation?
When a gamete containing a mutation for a genetic disorder or type of cancer is fertilised. The mutation is present in the new fetus formed.
When a mutation occurs in a gene that controls … it can cause cancer
A gene that controls cell division
What is a tumour?
A mass of abnormal cells caused by uncontrolled cell division
What two genes control cell division?
- Tumour suppressor genes (TSG)
- Proto-oncogenes
What do tumour suppressor genes do when functioning normally?
Slow cell division by producing proteins that stop cells dividing or cause them to die (apoptosis)
What happens is TSG becomes mutated?
Cannot produce protein which slows cells dividing division so cells will divide uncontrollably
When functioning normally, what do proto-oncogenes do?
Stimulate cell division by producing proteins that make cells divide
What happens if a proto-oncogene acquires a mutation?
The gene becomes overactive which stimulates cell division uncontrollably resulting in a tumour.
What is a mutated proto-oncogene called?
Oncogene
What are the two different types of tumours?
- Malignant - cancerous
- Benign - not cancerous
What are the differences between benign and malignant tumours?
- Benign - Grow slower and covered in fibrous tissue that stops cells invading other tissues
- Malignant - Grow rapidly and invade and destroy surrounding tissues. Cells can break off tumours and spread to other parts of the body in the blood stream or lymphatic system
How does abnormal methylation cause tumour growth?
When genes that control cell division are abnormally methylated, tumours can grow. When TSG are methylated too much (hypermethylation), the genes are not transcribed. This means cells can grow uncontrollably. When proto-oncogenes are not methylated enough (hypomethylation), they produce too much protein that encourages cell division.
What is the role of oestrogen in breast cancer?
- Oestrogen can stimulate certain breast cells to divide which can cause an increased risk of mutation in the DNA replication process.
- Since oestrogen can stimulate cell division, it is thought that if cells do become cancerous, oestrogen can aid rapid replication further.
