Mutagenesis

Question 1

What are the mechanisms that cells have to prevent and correct mutations?

Answer 1

Proofreading DNA polymerase(s)
Post-replication mismatch repair
DNA repair by homologous recombination
Cell cycle checkpoints
And others

Question 2

How do mutations happen?

Answer 2

Spontaneous or caused by environmental factors

Question 3

What environmental factors which can cause mutations to occur?

Answer 3

• Radiation

- Chemical mutagens

Question 4

How can radiation lead to mutation?

Answer 4

-Formation and repair of UV light-generated pyrimidine dimer

Question 5

What is a pyrimidine dimer?

Answer 5

Two adjacent thymines form photodiodes damaging the DNA and stoping DNA replication or transcription

Question 6

How can radiation mutation be corrected?

Answer 6

Use of photolyase and white light

Question 7

What can occur from trying to correct radiation mutation with photolyase and white light?

Answer 7

Point mutation

Question 8

What are three different types of chemical mutagens?

Answer 8

• Intercalating agents
• Base analogous
• Base modifying agents

Question 9

What is intercalating agents?

Answer 9

• Insert between base pairs causing a frameshift mutation to the right
• Planar molecules

Question 10

What is base analogous?

Answer 10

Incorporated into DNA in place of normal base causing mis-pair leading to base substitution

Question 11

What is base modifying agents?

Answer 11

Covalently alter a base causing it to mis-pair leading to base substitution

Question 12

What are examples of intercalating agents?

Answer 12

• Proflavin

- Acridine orange

Question 13

What is an example of base analogous?

Answer 13

-5-bromouracil (analogue of thymine)

Question 14

What does 5-bromouracil do?

Answer 14

Converts A to G

Question 15

What are three types of modifying agents?

Answer 15

• Deaminating agents (remove amino (-NH2) groups)
• Hydroxylating agents (add hydroxyl (-OH) groups)
• Alkylating agents (add alkyl (-CH3 or -CH3CH2) groups)

Question 16

What does alkylating agents do?

Answer 16

Convert G to A

Question 17

Can other single base mutations other than G to A occur via alkylating agents ?

Answer 17

Yes, T to C

Question 18

What is replication slippage and generation of short tandem repeats

Answer 18

• Short tandem repeats generated by replication slippage occurring in replication areas
• Looping out an area of DNA in one strand to use as a template causing an insertion of the loop

Question 19

What did Lederberg experiment in 1952 demonstrate?

Answer 19

• Mutations had occurred before selection

- Mutations are random - whether a particular mutation happens or not is unrelated to how useful that mutation would be

Question 20

How can the frequency of a mutation be increase?

Answer 20

By environmental factors

Question 21

Is mutations planned or random?

Answer 21

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