Question

This question is about DNA damage, repair and mutation.
a) State a type of mutagen that could produce a single base pair substitution mutation. Briefly describe how this mutagen can produce single base pair substitution mutations. [4 marks]
b) For your mutagen from (a), briefly describe the repair process that could repair the DNA damage. [4 marks]
c) Propose how a single base pair substitution can be a hypomorphic allele. Explain how your mutation fits the definition of a hypomorphic mutation. [3 marks]
d) State a type of mutation that is not a single base pair substitution. What type of mutagen could generate this type of mutation? Explain. [3 marks]

Answer 1

a) A type of mutagen that could cause single base pair mutation is - Base analogs. They are incorporated in the place of normal base as their structure is almost similar to natural bases with very little variation.

b) Base excision repair could be done to repair the DNA damaged by base analogs in which the faulty base is removed using enzymes like glycosylases and AP endonucleases.

c) Hypomorphic mutation is the type in which the normal function of the gene is lost . A single base pair mutation can be hypomorphic as the normal gene is altered due to base pair substitution resulting in formation of different protein.

d) A type of mutation that is not single base pair mutation is - Deletion mutation. This could be caused by both physical or chemical mutagens. Physical mutagen like UV radiation can cause dimerisation of bases which are eventually deleted from the DNA sequences causin mutation.