Molecular Biology Exam Ii

Front 1

What do DNA replication errors that change a base-pair sequence cause?

Back 1

Mutations

Front 2

What are the different kinds of mutations?

Back 2

Point mutations, Deletions, and Insertions

Front 3

What are Point Mutations?

Back 3

a substitution of one base for another

Front 4

What are Deletion Mutations?

Back 4

When bases get removed

Front 5

What are Insertion Mutation?

Back 5

When bases get added.

Front 6

Name the types of Point Mutations.

Back 6

Transition mutation and Transversion mutation

Front 7

What is a Transition Mutation?

Back 7

A switch from one purine:pyrimidine to the other purine:pyrimidine (example: AT to GC)

Front 8

What is a Transversion Mutation?

Back 8

A switch from purine:pyrimidine to pyrimidine:purine (example: AT to TA, AT to CG

Front 9

How are Point Mutations classed?

Back 9

By Expression

Front 10

When are Mutations important?

Back 10

If they change the expression of the gene.

Front 11

What do Missense Mutations do?

Back 11

They change in base-pair changes amino acid; they may change phenotype.

Front 12

What is a Neutral Mutation?

Back 12

If there is no change in function.

Front 13

What is a Silent Mutation?

Back 13

Base-pair changes without changing amino acid (due to redundancy)

Front 14

What is a Non-sense Mutation?

Back 14

A change in base-pair creates stop codon & truncated protein that almost always changes phenotype.

Front 15

What do deletions or insertions of base-pair numbers that are NOT multiples of 3 cause?

Back 15

Frame shift mutations

Front 16

What do Frame Shift Mutations cause?

Back 16

They produce non-functional protein and can change expression even if they are a multiple of three.

Front 17

What are some causes of Mutations?

Back 17

Mismatches during replication, Looping during replication, Spontaneous changes, Damage by water, Chemical damage, and Radiation Damage

Front 18

What do Mismatches during replication can cause?

Back 18

Point Mutations

Front 19

What does Looping during replication cause?

Back 19

Insertions or Deletions

Front 20

What does Template Loop cause?

Back 20

Deletions

Front 21

Replicated strand loop causes what?

Back 21

Insertions

Front 22

What do mismatches to enol form?

Back 22

Bases

Front 23

What is Depurination?

Back 23

When A or G is lost when base-deoxyribose bond

Front 24

What is Deamination?

Back 24

When you remove amine from cytosine get uracil (remove amine from methylated cytosine get thymine)

Front 25

How is Chemical Damage Induced?

Back 25

Induced by DNA exposure to alkylating or oxidizing chemicals

Front 26

What base is especially vulnerable to chemical damage?

Back 26

Guanine

Front 27

Name some Base modifiers.

Back 27

5-BDU, nitrous acid

Front 28

Name some Intercalating agents.

Back 28

acridine orange, ethidium bromide

Front 29

How is Radiation Damage induced?

Back 29

Induced by UV, gamma radiation, X-rays

Front 30

What can UV form?

Back 30

Thymine-Thymine Dimers

Front 31

What can cause a single or double bond to break?

Back 31

Gamma or X-rays

Front 32

How are DNA breaks repaired?

Back 32

By Recombination

Front 33

How are Replication mismatches repaired?

Back 33

By Polymerase Proofreading

Front 34

What is activated when proofreading fails?

Back 34

A mismatch repair system.

Front 35

What does a Mismatch Repair System correct?

Back 35

It corrects replication mismatches missed by proofreading

Front 36

What does Long Patch Repair rely on?

Back 36

The fact that E. coli adds methyl groups to A in GATC before replication

Front 37

In E. coli mismatch repair, what happens to GATC sites?

Back 37

GATC sites are hemi-methylated

Front 38

In which strands do methylation occur?

Back 38

Parental Strands

Front 39

In which strands does un-methylation occur?

Back 39

Daughter Strands

Front 40

What slides along new strands shortly after replication & binds to mismatch bulge?

Back 40

MutS protein

Front 41

To what does MutS bind to simultaneously?

Back 41

ATP

Front 42

What binds MutS-ATP when it pauses at mismatch?

Back 42

MutL protein

Front 43

What binds to un-methylated strand at hemi-methylated sites but stays inactive?

Back 43

MutH protein

Front 44

What activates MutH to nick un-methylated strand at nearest GATC?

Back 44

MutL:MutS

Front 45

What activates UvrD, a helicase, to unwind DNA from nick past the mismatch?

Back 45

MutL:MutS

Front 46

What removes bases from 3’ nick to MutL:MutS?

Back 46

Exonuclease I

Front 47

What removes bases from 5’ nick to MutL:MutS?

Back 47

Exonuclease VII

Front 48

What fills in gaps using methylated strand as template causing DNA ligase seals the break?

Back 48

DNA Pol III

Front 49

What repairs mismatches in humans?

Back 49

MSH/MLH

Front 50

Since no methlyation occurs in humans what can be used?

Back 50

Nicks at the primer site

Front 51

What does MSH detect in Humans?

Back 51

Bulge and interacts with PCNA

Front 52

How can Chemical or radiation damage can be repaired?

Back 52

By direct repair or excision repair systems

Front 53

What happens in Direct Repair?

Back 53

Photoreactivation repairs pyrimidine dimers and Methyltransferase transfers methyl from O6-methylguanine to an internal cysteine

Front 54

What happens in Excision Repair?

Back 54

See slide 19

Front 55

What happens if damage is not repaired prior to replication?

Back 55

The replication fork stalls at lesion.

Front 56

What will Special trans-lesion polymerase do?

Back 56

Synthesize over damage

Front 57

In E. coli what is UmuC complexed to?

Back 57

UmuD

Front 58

Give characteristics of Special trans-lesion polymerases.

Back 58

They are template dependent,
Nucleotide addition is independent of base-pairing, they are Highly error prone

Front 59

When do Normal replication polymerases return to the replication fork?

Back 59

Once undamaged DNA is reached

Front 60

When would a replication fork stall at lesion?

Back 60

As a Last Resort