3.2.11 Mutation and Cancer Flashcards
What is a gene mutation?
Changes in DNA base sequence of chromosomes
Name 2 types of errors that occur
- Substitution
- Deletion
What is deletion?
When one base is deleted
e.g. ATGCCT becomes ATCCT (G is deleted)
What is substitution?
When one base is substituted with another
e.g. ATGCCT becomes ATTCCT (G is swapped for T)
Name 3 types of substitution
- Nonsense mutation
- Missense mutation
- Silent mutation
What is a nonsense mutation?
Occurs if base change = stop codon
What is a missense mutation?
Occurs if base change = different amino acids being coded for
What is a silent mutation?
Substituted base, although different = codes for same amino acid
Why will not all substitution mutations lead to a change in the amino acid sequence of a protein?
Due to the degenerate nature of genetic code, some amino acids are coded for by more than one DNA triplet
Why will deletions always lead to changes in amino acid sequence?
From point of mutation base sequence changes/causes frame shift
What do mutagenic agents do?
Increases the frequency of mutations
Give an example of a mutagenic agent
e.g. UV radiation, ionising radiation, some chemicals and some viruses
Mutations occur _____
spontaneously
e.g. when DNA is misread during replication
What are acquired mutations?
Mutations that occur in individual cells after fertilisation
Describe how mutations can cause a tumour
- If mutations occur in genes that control rate of cell division (by mitosis) = uncontrolled cell division
- Uncontrolled cell division = tumour (mass of abnormal cells)
What is cancer?
Tumours that invade and destroy surrounding tissue