D1.3 Mutations and Gene Editing

Question 1

Define and Explain mutation

Answer 1

• A change in the genetic composition of a cell.
• A gene mutation is a change in the order of bases on a strand of DNA.
• Chromosome mutations are due to change in chromosome structure or the chromosome number of a cell.

Question 2

Explain Spontaneous mutation

Answer 2

• A mistake is made when DNA is copied during the production of gametes.

Question 3

Types of mutation and how they work

Answer 3

• Substitution
• Insertion
• Deletion

Question 4

Single-nucleotide polymorphisms (SNPs)

Answer 4

• Base substitution mutations are known as SNPs
• Are the most common type of genetic variation.
• Occurs when one nucleotide is replaced by another nucleotide in the DNA sequence.
• This change in the sequence may have an effect on the structure of the protein depending on whether substitution is synonymous or non-synonymous.

Question 5

Define Synonymous SNPs

Answer 5

• Synonymous substitutions: known as neutral mutations as they do not change the amino acid sequence due to the degeneracy of the genetic code.

Question 6

Define Nonsynonymous SNPs

Answer 6

• Nonsynonymous substitutions: change the amino acid sequence having different effects on protein function, possibly leading to protein malfunction.
• E.g. Nonsense and missense substitutions.

Question 7

Define Frameshift mutations

Answer 7

• Insertion, deletion and duplication all cause frameshift mutation.
• Insertion is when a nucleotide is inserted into a genetic sequence, which would shift the sequence to the right.
• Deletion is when a nucleotide in a genetic sequence is removed, which would shift the sequence to the left.

Question 8

Impact of frameshift mutations

Answer 8

• Results in alterations to the amino acid sequence coded by the DNA sequence, which will alter the structure of the protein, which is closely linked to their properties. Altered protein may no longer function.

Question 9

Define Mutagens

Answer 9

• Chemical or physical agents which have the ability to alter the genetic sequence.

Question 10

Examples of chemical mutagens

Answer 10

• Mustard gas
• Nitrous acid
• Ethyl urethane
• EMS & MMS
• Formaldehyde