GENETIC DIVERSITY

Question 1

What is substitution?

Answer 1

Nucleotide based is replaced with another

Question 2

What are the three types of gene mutation?

Answer 2

• Substitution
• Insertion
• Deletion

Question 3

What is insertion?

Answer 3

• An extra nucleotide base is inserted into the sequence causing ‘frameshift’
• All the subsequent bases are shifted down 1 place relative to the twin DNA strand

Question 4

What is deletion?

Answer 4

• The absence of a nucleotide, causing ‘frameshift’

* All the subsequent bases are shifted back 1 place relative to the twin DNA strand

Question 5

What are the three categories of mutation effects?

Answer 5

• Neutral
• Harmful
• Beneficial

Question 6

What are some neutral effects?

Answer 6

• May occur in phenotypically insignificant strand of DNA
• May not result in change of polypeptide primary sequence (because DNA is
degenerate)
• May result in a change of polypeptide primary sequence that does not affect
secondary/tertiary/quaternary structure of protein therefore protein function
unaffected
• May results in a change of polypeptide secondary/tertiary/quaternary structure but
where active site of protein remains the same therefore function still unaffected

Question 7

What are some harmful mutation effects?

Answer 7

Result in change in final protein shape where protein and active site is deformed and
therefore cannot fulfil function

Question 8

What are some beneficial mutation effects

Answer 8

• May result in change in final protein shape where the protein performs its function
better than it would have without the mutation
• This is the basis of natural selection and evolution
• The individual is better suited to survival and will pass on the mutation to its
offspring

Question 9

What is a mutation?

Answer 9

Change in base sequence of chromosomes

Question 10

When can mutations occur?

Answer 10

During DNA replication

Question 11

Why do not all base substitutions cause a change?

Answer 11

• Due to the
degenerate nature of the genetic code, not all base substitutions
cause a change in the sequence of encoded amino acids.

Question 12

What can increase rate of gene mutation?

Answer 12

Mutagenic agents

Question 13

What can mutations effect?

Answer 13

Mutations can affect 1 nucleotide base, or more than one adjacent base

Question 14

What is a point mutation?

Answer 14

Where only 1 base is affected

Question 15

What are the three types of mutation?

Answer 15

• Silent Mutation
• Missense Mutation
• Nonsense Mutation

Question 16

What is a silent mutation?

Answer 16

No change in amino acid sequence of polypeptide

Question 17

What is a missense mutation?

Answer 17

○ The mutation changes the code for 1 amino acid

○ 1 amino acid in the sequence is changes

Question 18

What is a nonsense mutation?

Answer 18

○ The mutation changes the code turning the triplet into a stop codon
○ Instructs the end of polypeptide synthesis
○ The polypeptide is shorter than it would normally be

Question 19

What is chromosomal non disjunction?

Answer 19

One pair of chromosomes fails to separate, so gamete and zygote have an extra chromosome

Question 20

How can mutations in the number of chromosomes happen?

Answer 20

Can occur spontaneously through chromosome non dis-junction during meiosis