gene mutation

Question 1

definition of gene mutation

Answer 1

it is a change in the sequence of DNA nucleotides in the gene

Question 2

gene mutation is most likely to occur….

Answer 2

when DNA is bring replicated during S phase of interphase

Question 3

3 types of gene mutations

Answer 3

• base pair substituition
• base pair addition
• base pair deletion

Question 4

4 possible impacts of mutation

Answer 4

• frameshift mutation
• missense mutation
• nonsense mutation
• silent mutation

Question 5

definition of base pair substituition

Answer 5

it is the replacement of one nucleotide base pair with another base pair in a gene

Question 6

definition of base pair addition

Answer 6

it is the gain of one or more nucleotide base pairs in a gene

Question 7

definition of base pair deletion

Answer 7

it is the loss of one or more nucleotide base pairs in a gene

Question 8

describe impact of frameshift mutation

Answer 8

in a frameshift mutation, reading frame is altered, all nucleotides downstream from the mutation will be improperly grouped into incorrect codons and read in different sets of three

Question 9

describe impact of nonsense mutation

Answer 9

in a nonsense mutation, a stop codon UAG/UAA/UGA is coded for in the gene, resulted in translation being terminated prematurely, producing a shortened polypeptide

Question 10

describe impact of missense mutation

Answer 10

in a missense mutation, there will be a change in amino acids with different property due to the different R group, leading to a change in polypeptide sequence/primary structure

Question 11

describe impact of silent mutation

Answer 11

in a silent mutation, due to the degeneracy of the genetic code, the same amino acid is still coded for and thus there is no change in polypeptide sequence/primary structure

Question 12

describe the mutation of sickle cell anaemia

Answer 12

1. this is due to a single base pair substituition whereby adenine replaces thymine in the gene that codes for the β chain.
2. as a result, in the mRNA formed, GUG (for amino acid valine) is coded for instead of GAG (for amino acid glutamic acid), resulting in a missense mutation
3. thus, hydrophobic valine replaces hydrophilic glutamic acid (at the 6th amino acid position). this results in a change in the 3D conformation of haemoglobin to produce HbS instead of HbA