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Microbiology > Exam Assignments > Flashcards

Exam Assignments Flashcards

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Biology 101 flashcards
1
Q

what is a codon

A

codons are groups of three mRNA nucleotides that code for a particular amino acid

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2
Q

What is the central Dogma of molecular biology

A

DNA to RNA to protein

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3
Q

what accounts for the high accuracy of DNA replication

A

replication is highly accurate due to the proofreading capability of DNA polymerase

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4
Q

DNA gyrase function

A

relaxes supercooling ahead of replication fork

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5
Q

DNA ligase function

A

makes covalent bonds to join new strands, Okazaki fragments, and new segments in excision repair

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6
Q

DNA polymerase

A

synthesize DNA, proofreading and facilitating DNA repair

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7
Q

topoisomerase

A

relaxes supercoiling ahead of replication fork, separates DNA circles at the end of DNA replication

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8
Q

why is DNA replication said to be semi conservative

A

one parental strand and one new strand

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9
Q

define the process of transcription

A

synthesis of a complementary mRNA strand from a DNA template

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10
Q

what are the three stages of transcription

A

initiation, elongation, termination

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11
Q

transcription cannot begin until

A

RNA polymerase binds to the promoter

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12
Q

generally, higher levels of transcription lead to higher levels of

A

translation

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13
Q

what does a riboswitch do

A

it is a post transcriptional control mechanism that can initiate or stop translation

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14
Q

how does a riboswitch work

A

riboswitch is a part of an mRNA molecule that binds to a substrate and changes the mRNA structure

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15
Q

define repression

A

inhibits gene expression and decreases enzyme synthesis. it is mediated by proteins called repressors that block transcription and the default position of a repressible gene is on

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16
Q

define induction

A

turns on gene expression. it is initiated by an inducer and the default position of an inducible gene is off

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17
Q

How are genes for lactose catabolism in E. coli transcribed when lactose is available

A

in the presence of lactose, metabolite of lactose (allolactose) which is the inducer binds to the repressor; the repressor cannot bind to the operator and transcription occurs

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18
Q

what type of operon is allolactose

A

inducible

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19
Q

are genes for lactose catabolism normally transcribed

A

no

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20
Q

what specific type of mutagen can result in thymine dimers

A

Nonionizing radiation (UV radiation)

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21
Q

two DNA repair mechanisms we discussed that are used to correct thymine dimers:

A

Photolyases and nucleotide excision repair

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22
Q

photolyases

A

enzymes that use visible light to separate the thymine dimers

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23
Q

nucleotide excision repair

A

enzymes cut out incorrect bases and fill in correct bases

24
Q

what is an auxotroph

A

mutant that has nutritional requirement absent in the parent

25
Q

describe replica plating

A
  1. sterile velvet is pressed on the grown colonies on the master plate and then cells from each colony are transferred from the velvet to new plates with different nutrients
  2. growth on plates is compared
  3. a colony that grows on the medium with histidine but could not grow on the medium without histidine is auxotrophic (histamine requiring mutant)
26
Q

describe the general mechanism of transformation in bacterial cells

A

genes are transferred from one bacterium to another as “naked” DNA. the recipient cell takes up fragments of DNA from donor cells and the donor DNA aligns with the complementary bases of the chromosomal DNA within the recipient cell. Recombination then occurs between the donor and receipt DNA resulting in a genetically transformed cell

27
Q

what other types of mechanisms result in DNA transfer among bacteria

A

transduction, conjucation (F+, HFR)

28
Q

vertical gene transfer

A

transfer of genes from an organism to its offspring

29
Q

horizontal gene transfer

A

transfer of genes between cells of the same generation

30
Q

what is the name of the test that indicated the degree to which a substance is mutagenic

A

Ames test

31
Q

what is the role of snRNPs

A

in eukaryotic cells, these removed introns and splice exons together

32
Q

why is PCR such an invaluable tool for researchers

A

PCR is a technique that allows for small target samples of DNA to be amplified quickly into large quantities, allowing for analysis by researchers, and it may be used for diagnostic tests for genetic diseases, as well as for detecting pathogens

33
Q

what is needed in order to preform the polymerase chain reaction

A

target DNA, nucleotides, primers, DNA polymerase (Tay polymerases) and the thermal cycler

34
Q

denaturation step in PCR

A

incubate at 94 degrees C to operate strands

35
Q

Priming step in PCR

A

incubate at 60 degrees C to allow primers to attach to ssDNA

36
Q

extension step PCR

A

incubate at 72 degrees C to allow DNA polymerase to copy the target DNA

37
Q

why do we need to use Taq Polymerase in PCR

A

able to withstand high temperatures required during the denaturation step of PCR, when the strands are seperated

38
Q

where does Taq polymerase come from

A

thermos aquaticus

39
Q

describe the role of restriction enzymes in the creation of recombinant DNA

A

restriction enzymes recognize and cut DNA at a specific site or nucleotide sequence and are able to cut the same way each time. some cut both strands in the same place creating blunt ends and some make staggered cuts in the two strands producing stick ends

40
Q

sticky ends have over hangs meaning they leave stretches of ssDNA at the ends of the fragments and are more useful in cloning because they will

A

hydrogen bond or base pair with another fragment in addition to the joining of the DNA backbones that occurs with the action of the enzyme DNA ligase

41
Q

what criteria must be met by a vector

A

vectors must be self replicating

42
Q

why are screening techniques utilized

A

in cloning its necessary to select the particular cell that contains your specific gene of interest and this could be difficult to do

43
Q

blue-white screening technique uses a plasmid containing

A

ampliilin resistance gene and B-galactosidase gene

44
Q

White colonies

A

produced by bacteria that have picked up the recombinant plasmid and will NOT hydrolyze lactose

45
Q

blue colonies

A

produced by bacteria with the intact LacZ gene to they will hydrolyze the X gal and produce blue colonies

46
Q

how can we silence genes

A

RNA interference

47
Q

how does RNAi work

A

inserts DNA encoding siRNA into a plasmid and then is transferred into the cell

48
Q

siRNAs are able to

A

bind to MRNA which is then destroyed by RNA-induced silencing complex or RISC

49
Q

Lytic cycle of T even bacteriophages
attachment

A

phage attaches by the tail fibers to the host cell

50
Q

Lytic cycle of T even bacteriophages
penetration

A

phage lysozyme opens the cell wall; tail sheath contracts to force the tail core and DNA into the cell

51
Q

Lytic cycle of T even bacteriophages
biosynthesis

A

production of phage DNA and proteins

52
Q

Lytic cycle of T even bacteriophages
maturation

A

assembly of phage particles

53
Q

Lytic cycle of T even bacteriophages
release

A

phage lysozymes breaks the cell wall, the cell lyses, and the released bacteriophages infect other susceptible cells in the vin city and viral multiplication is then repeated within those cells

54
Q

generalized transduction

A

bacterial genes can be picked up in a phage coat and transferred to another bacterium, any bacterial genes can be transferred during generalized transduction because the host chromosome is broken down into fragments (any of these can be packaged into a phage coat)

55
Q

specialized transduction

A

lysogenic phage mediates the packaging of bacterial DNA along with its own DNA in the same capsid so only certain bacterial genes are transferred

Microbiology (20 decks)

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