Mutations

Question 1

Mutations which affect the individual and are not passed on

Answer 1

Somatic Mutations

Question 2

Mutations which (normally) do not affect the individual but are passed on to children

Answer 2

Germ-line Mutations

Question 3

Mutations that enhance or reduce the organism’s survival and reproductive abilities are called…?

Answer 3

Selective Mutations

Question 4

Mutations that do not change the organism’s survival and reproductive abilities are called…?

Answer 4

Neutral Mutations

Question 5

Two general classifications for mutations…?

Answer 5

Base Substitutions and Length Mutations

Question 6

A change in the DNA sequence that does not change the amino acid sequence

Answer 6

Silent (Synonymous) Mutations

Question 7

A change in the DNA that causes the substitution of an amino acid for another one

Answer 7

Missense (Nonsynonymous) Mutations

Question 8

A change in the DNA that creates a new stop codon

Answer 8

Nonsense Mutations

Question 9

A mutation that eliminates a stop codon

Answer 9

Read Through Mutation

Question 10

A mutation that modifies an intron splice site

Answer 10

Cryptic Mutation

Question 11

Sickle cell anemia is an example of which type of mutation?

Answer 11

Missense Mutation

Question 12

A change in cis-elements that turns off gene expression

Answer 12

Suppression

Question 13

A change in cis-elements that expresses a gene in the wrong place

Answer 13

Ectopic Expression

Question 14

A change in cis-elements that expresses a gene at the wrong time

Answer 14

Ecchronic Expression

Question 15

TRED stands for…

Answer 15

Trinucleotide Repeat Expansion Diseases

Question 16

Common TREDs

Answer 16

Huntington’s Disease - CAG (>37)
Fragile-X - CGG (>200)
Friedreich’s Ataxia - GAA (>100)
Myotonic Dystrophy - CTG (>50)

Question 17

The process of TREDs expanding and becoming worse through generations

Answer 17

Genetic Anticipation

Question 18

Two types of base substitutions…?

Answer 18

Transition (A to G, G to A, C to T, or T to C)

Transversion (A to C/T, T to A/G, C to G/A, or G to C/T)

Question 19

Tautomeric Shifts

Answer 19

A and C shift from amino to imino
G and T shift from keto to enol
Can lead to transition mutations

Question 20

Base Analogs

Answer 20

Molecules similar to bases are added and have more frequent tautomeric shifts, leading to transitions
Ex: 5-bromouracil (5-BU) is a thymine analog and 2-aminopurine (2-AP) is an adenine analog

Question 21

Mutagenic Agents

Answer 21

Cause bases to become base analogs or interfere with normal pairing
Ex: Deamination by nitrous acid or sodium bisulfite (G blocks replication, C becomes U, and A becomes hypoxanthine)
Ex: Alkylating agents lead to base substitutions, e.g. ethylmethane sulfonate (EMS)

Question 22

Intercalating Agents

Answer 22

Chemicals that insert themselves into the DNA stack, blocking replication and transcription
Ex: Ethidium bromide, Proflavin, Acridine Orange

Question 23

Thymine Dimers

Answer 23

Adjacent T bases will dimerize to cyclobutane rings when exposed to UV light; replication adds a base to these areas to create frameshift mutations

Question 24

DNA Polymerase Proofreading/Mismatch Repair

Answer 24

DNA polymerase can recognize a mismatch, excise it, and replace it with the correct nucleotide

Question 25

Direct Repair

Answer 25

Changes nucleotides to correct structures; repairs dimerization and some base analogs

Question 26

Base Excision Repair

Answer 26

Fixes abnormal or modified bases by replacing entire nucleotide

Question 27

Nucleotide Excision Repair

Answer 27

1. Recognition (enzyme finds and tags mutation)
2. Excision (Several bases around damage are excised by exonucleases)
3. Replacement (Polymerase comes in to replace area
4. Ligase (Repairs nicks)

Question 28

Ways to repair thymine dimers

Answer 28

Photo Reactivation (Photolyase uses blue light to repair)
Nucleotide Excision Repair (UvrABC binds to 12-base region and endonuclease removes it)
Post Replication Repair (Occurs during replication to fix inability to replicate across dimer)

Question 29

Disease caused by inability to repair thymine dimers

Answer 29

Xeroderma pigmentosum