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Microbiology > Exam 3- Genome > Flashcards

Exam 3- Genome Flashcards

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Biology 101 flashcards
1
Q

What do most bacteria divide by?

A

binary fission

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2
Q

Where does replication in bacteria begin?

A

at a single origin (oriC)

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3
Q

What forms after initiation?

A

a replication bubble

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4
Q

Explain replication bubble.

A

contains two replication forks that move in opposite directions around the chromosome

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5
Q

Where does replication end?

A

the termination site (ter)

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6
Q

What does semiconservative mean in regards to DNA replication?

A

each new double-stranded DNA molecule contains one old (parental) strand & one new (daughter) strand

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7
Q

Bacterial chromosomes have a single…

A

point of origin

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8
Q

Eukaryotes usually have more than one…

A

origin of replication per chromosome

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9
Q

What has to happen in order to replicate DNA?

A

the double helix must unwind, exposing bases that can pair with another base on the growing strand

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10
Q

What does helicase do in DNA replication- initiation?

A

breaks the hydrogen bonds between nitrogenous bases, opening the DNA helix

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11
Q

What do single-stranded binding proteins do in DNA replication- initiation?

A

bind to the newly exposed single-stranded DNA & block formation of hydrogen bonds between nitrogenous bases

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12
Q

What does Topoisomerase II (DNA gyrase) do in DNA replication- initiation?

A

relieves the supercoiling of the chromosome by breaking & resealing the DNA

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13
Q

What does partial unwinding of the helix at the origin do?

A

generates a replication bubble with a replication fork at each end

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14
Q

What happens during DNA replication- elongation?

A

new DNA is synthesized by DNA polymerase III, using old DNA as a template

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15
Q

What is every new strand of SNA initiated with?

A

an RNA primer

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16
Q

What does primase do?

A

builds the short RNA primer

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17
Q

What does a protein sliding clamp do?

A

helps hold DNA pol III onto the chromosome during replication

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18
Q

What happens to the leading strand?

A

it is synthesized continuously

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19
Q

What happens to the lagging strand?

A

it is synthesized discontinuously in Okazaki fragments

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20
Q

What needs to happen to connect the small Okazaki fragments of the lagging strand into one continuous strand of DNA?

A

DNA pol I removes RNA primers & dills the resulting gap with DNA & DNA ligase seals the gaps between adjacent fragments of DNA

21
Q

What is at the end of replication?

A

2 concatenated double-stranded circular chromosomes

22
Q

What does Topoisomerase IV do?

A

cuts the circular chromosomes, then reseals the DNA after the two circular chromosomes separate

23
Q

What happens to newly synthesized DNA?

A

it is methylated

24
Q

What happens during replication prior to methylation?

A

old DNA is recognized by methylation; allowing mismatches to be repaired in the new strand of DNA

25
Q

What happens to uncorrected mistakes?

A

results in mutations

26
Q

When do spontaneous mutations occur?

A

during replication

27
Q

How is a species maintained?

A

by producing offspring that have DNA inherited from their parents

28
Q

What is the error rate of DNA replication in enteric bacteria?

A

estimated to be 1 in 10 million base pairs

29
Q

What is a mutation?

A

a base pair different from that of the pre-existing parent cell

30
Q

What is vertical gene transfer?

A

the transmission of an entire genome from parent to offspring

31
Q

What is horizontal gene transfer (lateral gene transfer)?

A

the acquisition of a piece of DNA from another cell, not through traditional reproduction

32
Q

What are the 3 main mechanisms of horizontal transfer?

A

transformation, transduction, conjugation

33
Q

Explain transformation.

A

the uptake & expression of exogenous free DNA from the environment

34
Q

What are competent cells?

A

cells that are able to take up free DNA & be transformed

35
Q

Explain transduction.

A

the transfer of DNA from one cell to another by a bacteriophage

36
Q

Explain generalized transduction.

A

involves the lytic life cycle of the phage & can more any gene

37
Q

Explain specialized transduction.

A

lysogenic cycle, moves only genes connected to site of prophage insertion

38
Q

What is conjugation?

A

transfer of DNA between bacteria through direct contact

39
Q

What does conjugation require?

A

cell-to-cell contact, special transfer plasmid

40
Q

What can F-factor integrate into?

A

the chromosome

41
Q

What happens when F factor integrates into the chromosome of an F+ cell?

A

the cell becomes a high frequency of recombination (Hfr) cell

42
Q

What species does conjugation mostly occur in?

A

Gram-negative species

43
Q

Describe Agrobacterium tumefaciens.

A
  • Rhizobium radiobacter
  • bacterial species that causes crown gall disease (tumors)
  • contains a tumor-inducing plasmid (Ti) that can be transferred via conjugation to plant cells
  • used in lab for inserting foreign genes into plants
44
Q

Once a new piece of DNA has entered a cell, what happens to it?

A

if the new DNA is a self-replicating plasmid, the plasmid will coexist in the cell separate from the host chromosome

45
Q

What is recombination?

A

an enzyme-mediated process in which two DNA molecules exchange portions by breaking & reforming their sugar phosphate backbones

46
Q

Explain DNA repair.

A
  • useful to fix mutations
  • does not involve foreign DNA
  • cells with damaged chromosomes can use DNA from other cells of the same species to repair the damaged region
47
Q

What are the consequences of horizontal transfer?

A

bacteria can gain new metabolic capabilities, antibiotic resistance, increased virulence

48
Q

Describe Corynebacterium diphtheriae.

A

Gram positive; pleomorphic rod, no specific arrangement, produces diphtheria toxin, toxin is encoded by a bacteriophage that has integrated into the bacterial chromosome

49
Q

Describe Diphtheria.

A
  • old disease not commonly seen anymore
  • symptoms: sore throat, fever, swollen glands in neck, pseudomembrane
  • transmission by direct contact, or through air
  • treatment: antitoxin & antibiotics
  • there is a vaccine

Microbiology (11 decks)

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