TOPIC 8A Flashcards
What is a mutation?
Any changes to the base (nucleotide) sequence of DNA is called a mutation.
Mutations can be caused by errors during DNA replication.
What can increase the rate of mutation?
The rate of mutation can be increased by mutagenic agents.
What are the 6 types of mutations that can occur?
- Substitution
- Deletion
- Addition
- Duplication
- Inversion
- Translocation
What happens in a substitution mutation?
One or more bases are swapped for another,
e.g.
ATGCCT becomes ATTCCT
What happens in a deletion mutation?
One or more bases are removes,
e.g.
ATGCCT becomes ATCCT
What happens in an addition mutation?
One or more bases are added,
egg,
ATGCCT becomes ATGACCT
What happens in a duplication mutation?
One or more bases are repeated,
e.g. ATGCCT becomes ATGCCCCT
What happens in an inversion mutation?
A sequence of bases is reversed,
e.g. ATGCCT becomes ACCGTT
What happens in 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.
A mutation in what gene can increase the chance of developing breast cancer?
BRCA1
What are hereditary mutations?
If a gamete containing a mutation for a genetic disorder or type of cancer is fertilised, the mutation will be present in the new fetes formed - these are called hereditary mutations because they re passed onto the offspring.
How do not all mutations in DNA affect the order of amino acids?
(see bottom of page 180 in the revision guide)
How do some mutations in DNA affect the order of amino acids?
(see top of page 181 in the revision guide)
What 3 ways can mutagenic agents increase the rate of mutation?
- Acting as a base
- Altering bases
- Changing the structure of DNA
(see page 181 in the revision guide)
What are acquired mutations?
Mutations that occur in individual cells after fertilisation (e.g. in adulthood) are called acquired mutations.
What can happen if threes an acquired mutation in a human cell?
If these mutations occur in the genes that control the rate of cell division (by mitosis), it can cause uncontrolled cell division.
If a cell divides uncontrollably the result is a tumour - a mass of abnormal cells. Tumours that invade and destroy surrounding tissue are called cancers.
There are 2 types of gene that control cell division - tumour suppressor genes and proto-oncogenes. Mutations enthuse genes can cause cancer.
What 2 types of genes control cell division?
- Tumour suppressor genes
- Proto-oncogenes
How can a mutation in a tumour suppressor gene cause cancer?
Tumour suppressor genes can be inactivated if a mutation occurs in the DNA sequence.
When functioning normally, tumour suppressor genes slow cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis).
If a mutation occurs in a tumour suppressor gene, the protein isn’t produced. The cells divide uncontrollably (the rate of cell division increases) resulting in a tumour.
(see page 182 in the revision guide for pictures)
What is apoptosis?
A cell self-destructing.
How can a mutation in a proto-oncogene cause cancer?
The effect of a porto-oncogene can be increased if a mutation occurs in the DNA sequence. A mutated port-oncogene is called an oncogene.
When functioning normally, proto-oncogenes stimulate cell division by producing proteins that make cells divide.
If a mutation occurs in a porto-oncogene, the gene can become overactive. This stimulates the cells to divide uncontrollably (the rate of division increases) resulting in a tumour.
What are the 2 different types of tumour?
- Benign
- Malignant
What is a benign tumour?
Benign tumours are not cancerous. They usually grow slower than malignant tumours and are often covered in fibrous tissue that stops cells invading other tissues. Benign tumours are often harmless but they can cause blockages and put pressure on organs. Some benign tumours can become malignant.
