20.1: Gene mutations

Question 1

What is a mutation

Answer 1

Any change to the structure or arrangement of DNA in an organism

Question 2

What is a Gene Mutation

Answer 2

A Gene Mutation is any change to one or more nucleotide bases, or arrangement of nucleotide bases in DNA

Question 3

Consequences from a gene mutation

Answer 3

A gene mutation may lead to a change in the amino acid sequence of a polypeptide.

Question 4

6 Different types of Gene Mutation

Answer 4

Addition

Deletion

Substitution

Translocation

Inversion

Duplication

Question 5

What is a Substitution Mutation

Answer 5

A substitution mutation is a mutation in which one nucleotide base is substituted for another.

This has 3 different consequences:

1. Formation of 1 of 3 stop codons, stopping the production of the resultant polypeptide
2. Formation of a codon for a different amino acid
3. Formation of a codon for the same amino acid, because the code is degenerate

Question 6

What is a Deletion Mutation

Answer 6

A deletion mutation is a mutation in which one nucleotide base is deleted.

This causes a frame shift to the LEFT

Question 7

What is an Addition Mutation

Answer 7

An addition mutation is a mutation in which an extra base is inserted.

This causes a frame shift to the RIGHT

Question 8

What is a Duplication Mutation

Answer 8

A duplication mutation is a mutation in which one or more bases are duplicated and repeat.

This causes a frame shift to the RIGHT

Question 9

What is an Inversion Mutation

Answer 9

An inversion mutation is a mutation in which a group of bases are separated from DNA and join back in the same position but back to front

Question 10

What is a Translocation Mutation

Answer 10

A translocation mutation is a mutation in which a group of bases are separated from one chromosome and are inserted into the base sequence of a different chromosome.

Question 11

Causes of Mutations

Answer 11

1. DNA replication, random
2. Mutagenic agents e.g

• Ionising radiation which disrupt the structure
• Chemicals such as nitrogen dioxide which may alter the structure or disrupt transcription. Carcinogens

Question 12

3 things that may occur from a substitution reaction

Answer 12

1. 1 of 3 stop codons formed
2. Same amino acid, different triplet
3. Different amino acid, different triplet

Question 13

Benefits of Mutations

Answer 13

Produce genetic diversity necessary for natural selection and speciation

Question 14

Costs of mutations

Answer 14

Almost always produce harmful effects on an organism and make it less well suited to its environment

Question 15

Mutations occurring in body cells vs gametes

Answer 15

Mutations that occur in body cells lead to disruption of normal cellular activities e.g. cell division - causing cancer