Point Mutations

Question 1

What is a point mutation?

Answer 1

A mutation affecting single nucleotide change

Question 2

What are the two ways a point mutation can be classified?

Answer 2

• Mutations reffering to what happens to base sequence
• Mutations reffering to what happens to amino acid formed

Question 3

What is a Point Mutation - Deletion?

Answer 3

• A nucleotide is lost from DNA sequence
• Results in a frameshift

Question 4

What is a frameshift?

Answer 4

When reading frame is moved (the section of 3 bases)

Question 5

What is the effect of a Deletion Point Mutation?

Answer 5

• Codons not being read properly
• Because bases are read in triplets, and all subsequent bases would shift by one base
• Usually amino acid sequence will be enitirely different

Question 6

Desrcibe seriousness of Deletion Point Mutation

Answer 6

• Very Serious mutations
• Because lots of amino acids are changed
• So, protein will have a different shape
• Will likely be non-functional

Question 7

What is another name of Insertion Point Mutations?

Answer 7

Adition Point Mutation

Question 8

What is an Addition Point Mutation?

Answer 8

• When a nucleotide is added to DNA sequence

Question 9

What are the effects and seriousness of Insertion Point Mutation?

Answer 9

Same as Deletion

Question 10

What is a Substitution Point Mutation?

Answer 10

Substitution mutations result in change of one base

Question 11

What are effects of Substitution Point Mutation?

Answer 11

• No frameshift occurs
• Only 1 amino acid potentially changed
• So, protein may still be functional as before

Question 12

What is a mis-sense mutation?

Answer 12

• Occurs when a change in base leads to different amino acids being coded for
• Polypeptide will have a single amino acid that is different

Mutation reffering to amino acid change

Question 13

How serious is a mis-sense mutation?

Answer 13

• Not as serious as other mutations
• Only 1 amino acid changed
• Protein may still function as before

Question 14

What is a nonsense mutation?

Answer 14

• Occurs when substitution of base leads to a premature stop-codon being coded for
• This leads to premature end to synthesis of polypeptide

FInal protein formed is refered to as truncated protein

Question 15

Describe seriousness of Nonsense Mutation

Answer 15

• Successfull synthesis of final proetin is very unlikely
• Almost certainly not be able to function normally

Question 16

What is a Silent Mutation?

Answer 16

Occurs when substitution of base still codes for same amino acid as original base

Question 17

How are silent mutations possible and what are the effects?

Answer 17

• Possible due to degenerate code
• No effect on production of final polypeptide

Question 18

What is Degenerate Code?

Answer 18

Multiple codons code for same amino acid