Chapter 4: 4.5 Types of DNA Mutations

Question 1

When do mutations happen?

Answer 1

Mutations in DNA occur when there is a change in the normal DNA sequence

Question 2

Define:

Point Mutations

Answer 2

Only one base pair is mutated

Question 3

How can point mutations arise due to? (4)

Answer 3

• Errors in DNA replication
• Environmental exposure to damaging agents like UV light radiation etc.
• Harmful chemicals/toxins
• Byproducts of normal cell metabolism (e.g. lipid oxidation)

Question 4

What are the types of point mutations?

Answer 4

1. Nonsense Mutation
2. Missense Mutation
3. Silent Mutation

Question 5

Define:

Nonsense mutations

Answer 5

A premature stop codon is introduced into a sequence
* E.x. UGC (Cysteine) to UGA (Stop)

Question 6

Define:

Missense mutations

Answer 6

A change to the amino acid sequence
* E.x. UGC (Cysteine) to UGG (Tryptophan)

Question 7

Define:

Silent mutations

Answer 7

No change to the amino acid sequence
* E.x. UGC (Cysteine) to UGU (Cysteine)

Question 8

True or False:

Mutations can be beneficial

Answer 8

True, mutations can be:
* Beneficial
* Benign
* Harmful

Question 9

Define:

Beneficial mutations

Answer 9

Improves the fitness of an organism (e.g. resistance to a virus, lactose tolerance)

Question 10

Define:

Benign mutations

Answer 10

Does not change the overall fitness of an organism (e.g. change in eye color or silent mutations)

Question 11

Define:

Harmful mutations

Answer 11

Negatively impacts the fitness of an organism (e.g. development of diseases like cancer and birth defects)

Question 12

What’s a mnemonic for nonsense mutations causing stop codons?

Answer 12

STOP the NONSENSE

Question 13

When a nucleotide is replaced by another, it is called a…

Answer 13

Base substitution

Question 14

True or False:

Point mutations are most commonly base subsitutions

Answer 14

True

Question 15

What are the types of base substitutions?

Answer 15

1. Transitions
2. Transversions

Question 16

Define:

Transition base substitutions

Answer 16

Purine for purine, pyrimidine for pyrimidine
* E.x. A for G, C for T

Question 17

Define:

Transversion base substitutions

Answer 17

Purine for pyrimidine and vice-versa
* E.x. A for T, C for G

Question 18

What is a mutation that causes the changes in the reading frame of the nucleotide sequence called??

Answer 18

Frameshift mutations

Question 19

What are frameshift mutations caused by?

Answer 19

Insertions or deletions of fragments of DNA

Question 20

DNA sequence codes for…

Answer 20

Proteins

Question 21

How many nucleotides code for one amino acid?

Answer 21

3