Chapter 35

Question 1

True or False: DNA damage is inevitable, resulting from errors in replication or environmental insults

Answer 1

True

Question 2

Name 2 things DNA damage can lead to

Answer 2

• Cell death
• Uncontrolled replication (as when normal cells are transformed into cancer cells)

Question 3

Repair systems

Answer 3

exists to recognize and repair damage to DNA

Question 4

Simplest source of DNA damage

Answer 4

Incorporation of incorrect base during replication that escapes the notice of the proofreading capabilities of DNA polymerase

Other errors include insertion, deletion, or breaks in one or both strands, which may halt DNA synthesis altogether

Question 5

Point mutations

Answer 5

small scale type of mutation

There is a single nucleotide exchange ~ can result in a silent mutation, neutral mutation, missense mutation, or nonsense mutation

Question 6

Small scale mutations

Answer 6

can include insertions in which extra nucleotides are inserted ~ resulting in gene frame shift or a splice site mutation (more major change)

Question 7

Large scale mutations

Answer 7

chromosomal structure can be changed and altered ~ this will have more drastic effects and will impact many more genes

Question 8

Result of Mutations - Loss of function:

Answer 8

gene product has less or no function ~ often recessive

Question 9

Result of Mutations - Gain of Function:

Answer 9

gene product gains new, abnormal function ~ often dominant

Question 10

Result of Mutations - Dominant Negative:

Answer 10

gene product (often inactive) antagonizes product of normal allele

Question 11

Result of Mutations - Lethal:

Answer 11

lead to death of organism

Question 12

Result of Mutations - Back Mutation or Reversion:

Answer 12

point mutation that restores original sequence and phenotype

Question 13

Result of Mutations

Answer 13

Some mutations are advantageous ~ these mutations are noted by the process of evolution as organisms adapt to survive in different environmental conditions in response to different stressors

When the mutation is beneficial and allows for fitness of the organism, that mutation is passed on to progeny

Question 14

DNA Damage: Detect & Repair

Answer 14

DNA repair systems follow the following mechanistic outline:

1. Recognize the inappropriate base(s)
2. Remove the inappropriate base(s)
3. Repair the resulting gap w/ a DNA polymerase and DNA ligase

First DNA repair mechanism: occurs when DNA polymerase proofreads the newly synthesized DNA and corrects mismatches

Repair mechanism is dependent on “other” polymerases as opposed to the main DNA polymerase; thus, it may..

• Not be as precise as normal replicative process
• Introduce mutations

Types: mismatch, base-excision, mucleotide-exciison

Question 15

Mismatch-Repair-Systems

Answer 15

Mismatch repair systems: correct errors that were not corrected by proof-reading

In E. coli, two proteins are required for mismatch repair

• One to recognize the error
• One to recruit an endonuclease to cleave the DNA where the error has taken place

Direct repair corrects mistakes w/o having to remove any fragments of DNA