mutations

Question 1

mutations

Answer 1

a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

Question 2

frequency and repair of genes

Answer 2

• mutations can occur continuously in somatic cells and gametes
• probability of a gene mutation is 10^-10 per cell generation
• faulty DNA can be repaired by specific DNA enzymes e.g DNA glycosylase cuts out the wrong base and then repaired by DNA polymerase

Question 3

causes of point mutations

Answer 3

• changes in an individual gene due to miscopying of one or more nucleotides
• deletion or insertion of a nucleotide results in a frameshift
• substitution results in the change of one base

Question 4

types of substitutions

Answer 4

• silent mutation: no amino acid change, redundancy in code
• missense: change in amino acid
• nonsense: changes to a stop codon

Question 4

mutagenic agents

Answer 4

• radiation: UV radiation, X-rays
• chemicals: cigarette smoke, benzoyl peroxide, nitrate and nitrate preservatives, barbecuing
• infectious agents: HPV, helicobacter pylori-bacteria spread in contaminated food