9.1 - Genetic Mutations

Question 1

3 mutagenic agents

examples of mutagenic agents:

Answer 1

high energy radiation such as UV light
ionising radiation such as X-rays
toxic chemcials such as peroxides

Question 2

What are mutagenic agents?

Answer 2

environmental factors which increase the mutation rate of cells

Question 3

How would a mutation affect an enzyme for example? What could happen to collagen?

Answer 3

1. the shape of the active site on an enzyme changes
   * the substrate is no longer complementary in shape to the active site
   * a structural protein may lose its strength if it changes shape such as collagen

Question 4

What do a small number of mutations cause?

Answer 4

codes for a significantly altered polypeptide with a different shape
* can affect the ability of the protein to perform its function

Question 5

What is the effect of gene mutations on the polypeptide generally?

Answer 5

most don’t alter the polypeptide it only slightly changes but the appearance/function remains the same

Question 6

Nonsense mutations - what is it? what happens to the polypeptide chain? and what is an example of this?

Answer 6

• mutations that creates a premature stop codon
• the polypeptide chain produced is incomplete and affects the final protein structure and function
• an example is cystic fibrosis

Question 7

Missense mutations and what is an example of this?

Answer 7

• mutations that alter a single amino acid in the polypeptide chain
• an example is sickle cell anaemia which is due to a single amino acid changing

Question 8

What are silent mutations? and why is this the case?

Answer 8

• mutations which don’t alter the amino acid sequence of the polypeptide
• this is due to the genetic code being degenerate

Question 9

What will the subsitution mutation only affect?

Answer 9

it only affects the amino acid formed by the triplet affected by the mutation

Question 10

What happens when there’s a subsitution mutation?

Answer 10

a base in the DNA sequence is randomly switched out for another base

Question 11

Deletion of nucleotides mutation - other type of mutation which can occur from deletion

Answer 11

• occurs when a nucleotide/base is randomly deleted from the DNA sequence
• changes the amino acid coded for like an insertion mutation
• has a domino effect on the oncoming bases (frameshift mutation)

can dramatically change the amino acid sequence produced from this gene and therefore the ability of the polypeptide to function

Question 12

Types of substitution mutations

Answer 12

silent
missense
nonsense

Question 13

Types of DNA base sequence mutations

Answer 13

• deletion
• substitution

Question 14

What benefit is there to genes due to the genetic code being degenerate?

Answer 14

most mutations don’t alter the polypeptide or only slightly that its function isn’t changed

Question 15

What does the DNA base sequence determine and how does a mutations affect this?

Answer 15

• determines the primary structure
• mutations in a gene can sometimes lead to a change in the polypeptide that the gene codes for

Question 16

How often do mutations occur?

Answer 16

continuously

Question 17

What is a gene mutation?

Answer 17

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