4: GENETICS - MUTATIONS Flashcards
1
Q
What is a gene mutation?
A
a mutation that involves a change in the DNA base sequence of chromosomes
2
Q
What are 2 types of gene mutations that can occur?
A
- deletion
- substitution
3
Q
What effect does deletion of a base have on the sequence of amino acids and the polypeptide formed?
A
- base is deleted so no. of bases changes causing a shift in the base triplets after the point where the base was deleted
- this means there is a change in the sequence of amino acids
- H bonds, ionic bonds and disulfide bridges
- therefore the tertiary structure of the protein is altered
- this means that the protein produced will be non-functional
4
Q
What are the 2 possible effects that the substitution of a base could have on the sequence of amino acids and the polypeptide formed?
A
- could result in a different sequence of amino acids, which would produce a non-functional protein
- however the substitution could have no effect on the sequence of amino acids as the genetic code is degenerate meaning more than 1 codon can code for a specific amino acid
5
Q
What causes DNA mutations to occur?
A
- nothing
- mutations occur spontaneously
6
Q
What do mutagenic agents do?
A
- increase rate of gene mutation
- increase probability of mutation occurring
7
Q
What are examples of mutagenic agents?
A
- UV radiation
- ionising radiation (eg: X rays, gamma rays)
- chemicals (eg: benzene, bromine, nitrosamines, arsenic)
- viruses (eg: HPV)
8
Q
What are chromosome mutations caused by?
A
errors during meiosis
9
Q
What do chromosome mutations lead to and why?
A
- lead to inherited conditions
- this is because the errors are present in the gametes (hereditary cells)
10
Q
What is chromosome non-disjunction?
A
- failure of the chromosomes to separate properly in meiosis
- so new cells will have an extra copy of the chromosome/ an extra copy of part of the chromosome
