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Microbiology > Exam 3 - Mutations > Flashcards

Exam 3 - Mutations Flashcards

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Biology 101 flashcards
1
Q

What are mutations?

A

Stable, heritable changes in the base sequence of DNA

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1
Q

T/F
Mutations can only be spontaneous OR induced.

A

F, can be both.

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2
Q

Where and how often do spontaneous mutations occur?

A

The natural environment, infrequently and randomly

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3
Q

What is the general rate of mutation?

A

between 1 in 10,000 and 1 and 1trillion
(low due to cellular repair mechanisms)

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4
Q

Spontaneous mutations can occur from: (3)

A

base substitutions
removal or addition of nucleotides
transposable elements

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5
Q

What is the most common type of spontaneous mutation?

A

Base substitutions

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6
Q

How do base substitutions occur?

A

From mistakes during DNA synthesis, incorrect base is incorporated into DNA

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7
Q

Point mutations def.

A

One base pair is changed

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8
Q

What are the (3) effects/types of base substitutions?

A

Silent mutations
Missense mutation
nonsense mutation

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9
Q

Silent mutations def.

A

Result from a nucleotide change that generates a codon which still specifies the wild type amino acid

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10
Q

Missense mutation def.

A

amino acid substitution mutation

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11
Q

Nonsense mutation def.

A

mutation that changes an amino acid codon to a stop codon

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12
Q

Base substitutions in the third position of a codon would most often cause what type of mutation?

A

Missense
Asense
Nonsense
Silent (a majority of the time, not all)

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13
Q

Generally, what does the removal or addition of nucleotides do to the genetic code?

A

Shifts the translational reading frame (codons)

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14
Q

Frameshift mutation def.

A

occurs when shifting of the codons occurs; affects all amino acids downstream from addition or deletion

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15
Q

Transposable elements def.

A

special DNA segments that can move spontaneously from gene to gene (transposons)

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16
Q

Transposition can be either _____________ or _____________

A

conservative; replicative

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17
Q

Conservative transposition

A

Transposon is completely removed from one area of a chromosome and reinsterted elsewhere (cut+paste)

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18
Q

Replicative transposition

A

A copy of the transposon is inserted elsewhere in the chromosome (copy+paste)

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19
Q

T/F
Mutations are essential for understanding genetics

A

True

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20
Q

Induced mutations def.

A

Mutations that are intentionally produced

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21
Q

Induced mutations can be done via (3)

A

Chemical mutagens
Transposition
Radiation

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22
Q

Chemical mutagens (4)

A

Nitrous acid
Alkylating agents
Base analogs
Intercalating agents

23
Q

Nitrous acid func.

A

Converts amino group to a keto group
»cytosine to uracil

24
Q

Alkylating agents func.

A

Alters hydrogen bonding of bases
»nitrosoguanine

25
Q

Base analog def.

A

Chemicals that are structually similar to the nitrogenous bases but have slightly altered base pairing properties

26
Q

Intercalating agents def

A

Molecules that insert themselves between adjacent bases
»ethidium bromide

27
Q

What is it called when transposons are inserted into cells to cause mutations?

A

Induced transposition

28
Q

What are the two types of radiation?

A

Ultraviolet light
X-rays

29
Q

Ultraviolet light mutation func.

A

causes covalent bonding between adjacent thymine bases

30
Q

Ultraviolet light ultimately forms what?

A

thymine dimers

31
Q

Thymine dimers func.

A

distorts DNA

32
Q

X-ray mutation func.

A

causes breaks in sugar-phosphate backbone of DNA
»breaks in both strands are often lethal

33
Q

Mechanisms of DNA repair (4)

A

Proofreading
Mismatch Repair
Nucleotide excision repair
Photoreactivation

34
Q

Proofreading

A

DNA polymerase removes an incorrectly added base and the correct base is added

35
Q

Mismatch repair occurs in _______ organisms

A

most

36
Q

Mismatch repair in gram negative bacteria does what?

A

Parent strand is methylated during DNA replication; the unmethylated daughter strand is scanned by mut proteins

37
Q

Mut protein scanning process

A

Bind to incorrectly paired daughter strand sections
recruit exonuclease to cut out mutated section
DNA polymerase rebuilds removed section

38
Q

Nucleotide excision repair actions

A

Exonuclease removes thymine dimer;
DNA polymerase able to rebuild

39
Q

Photoreactivation

A

Photolyase is activated by sunlight
Binds to thymine dimers

40
Q

photolyase binding to thymine dimers does what

A

breaks down dimer; allowing thymines to reform H-bonds with adenines

41
Q

Gene transfer mechanisms (3)

A

DNA-mediated transformation
Transduction
Conjugation

42
Q

Two events that occur in gene exchange

A

1) Donor DNA is transferred and accepted by recipient cell
(Donor DNA is either transformed/Transducted/Conjugated)
2) Donor DNA is integrated into the recipient cell’s chromosomes

43
Q

Transformation func.

A

involves the transfer of naked DNA from the environment to the recipient cell–> naked DNA is integrated into recipient chromosome

44
Q

Naked DNA that is integrated into a chromosome does what

A

Replaces the homologous gene on the chromosome of the recipient cell

45
Q

Natural transformation occurs when bacterial cells are

A

competent

46
Q

Competence def. (bio)

A

A condition where bacterial cells are capable of taking up and integrating larger fragments of DNA

47
Q

When does competence occur in the cell growth phase?

A

Late log, early stationary phase

48
Q

Artifical competence

A

ability to render cells artifically competent through electroporation

49
Q

Transduction def.

A

Bacterial DNA that is transferred from donor to recipient via a bacterial virus

50
Q

Transduction process

A

Phage infects a new bacterial cell and inserts DNA into cell
DNA is integrated and mis-matched pairs are repaired

51
Q

Two types of transduction are

A

Generalized
»any gene of donor can be transferred
Specialized
»only specific genes can be transferred

52
Q

Specialized transduction

A

During excision phase of viral lysogenic cycle, part of the host cell DNA is incorporated into virus

53
Q

Conjugation

A

mediated by F plasmid

54
Q

F factor

A

Plasmid that codes for fertility amongst cells (F factor)

Microbiology (15 decks)

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