D1.3 - mutations (5c)

Question 1

what is a gene mutation?

Answer 1

gene mutations are structural changes to genes at a molecular level, which change the base sequence of DNA

Question 2

what are the 3 types of gene mutation?

Answer 2

substitutions - where one base is replaced with another
insertions - where a base is added into a gene
deletions - where a base is removed from a gene

Question 3

which type of mutation forms a SNP?

Answer 3

a base substitution mutation forms a SNP

Question 4

what are the consequences of base substitutions on the process of protein synthesis?

Answer 4

1. template strand of DNA will have a different triplet
2. different codon produced within the mRNA molecule
3. different tRNA will bind to the modified mRNA
4. different amino acid may be incorporated into the polypeptide chain
5. polypeptide could fold into a different shape with a different function

Question 5

what is a missense mutation?

Answer 5

a missense mutation is a change in amino acid causes a different protein to be made during translation

Question 6

what is a silent mutation?

Answer 6

a silent mutation is that due to degeneracy of the genetic code, a mutation may or may not change a single amino acid in the polypeptide

Question 7

what is a nonsense mutation?

Answer 7

a nonsense mutation is when a stop codon is generated in the base substitution, so the protein made is truncated (cut short)

Question 8

why is the amino acid change not guaranteed following a base substitution reaction?

Answer 8

the degeneracy of the genetic code means that more than one codon codes for a particular amino acid

Question 9

what are 3 causes of gene mutation?

Answer 9

• chemical mutagens such as benzene or polystyrene
• mutagenic forms of radiation such as UV light and radium
• errors in DNA replication or repair

Question 10

what is the randomness of mutations?

Answer 10

mutations can occur anywhere in a base sequence of a genome, but some bases such as CpG sites have a higher probability of mutation than others

Question 11

where do most mutations occur and what is the impact?

Answer 11

most mutations occur in non-coding regions which can impact the gene expression or disrupt functional roles of DNA
- no natural mechanism is known for making a deliberate change to particular bases with the purpose of changing a trait