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mechanisms of microbial genetics Flashcards

1
Q

what are the functions of DNA

A

store genetic material
direct and regulate the construction of proteins necessary to a cell for growth

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2
Q

what is a gene

A

dna that is read or transcribed to produce an RNA molecule through transcription

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3
Q

what is translation

A

when mRNA provides information for the ribosome to catalyze protein synthesis

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4
Q

what is gene expression

A

the synthesis of a specific protein with a sequence of amino acids that is encoded in the gene

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5
Q

what are the stages of replication, transcription and translation

A

initiation
elongation (polymerization)
termination

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6
Q

What is central dogma

A

the flow of genetic information from DNA to RNA

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7
Q

what is the process from dna to a protien

A

DNA>transcription>RNA>translation

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8
Q

What is replication

A

the process of DNA being copied

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9
Q

what is the semiconservative replication model

A

when 2 strands of the double helix separate and each strand is the template for for a complementary strand

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10
Q

what did meselson and stahl use in their dna experiments

A

a heavy isotope of nitrogen (15N) that was incorporated into nitrogenous bases and then DNA and E. coli

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11
Q

what medium was the e coli cultured in for dna testing

A

one with 14N and allowed to grow for one generation

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12
Q

how is dna separated

A

using and ultracentrifuge where dna forms bands according to its desity

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13
Q

what was expected of dna after being ultracentrifugated

A

15n would form a band at higher density than those grown in 14N

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14
Q

what were the results of the first generation dna

A

the band was between 15n and 14n

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15
Q

what happened to cells grown as a second generation in 14n

A

one band was between 14n and 14 and the second band corresponded to th second band of DNA

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16
Q

how long does it take E. coli dna to replicate

A

42 minutes

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17
Q

what DNA polymerase is required for DNA synthesis

A

DNA pol 3

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18
Q

what are DNA pol 1 and DNA pol 2 used for

A

repair

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19
Q

what does DNA pol 3 do

A

adds deoxyribonucleotides to a nucleotide on the template strand

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20
Q

where does DNA get the energy for replication

A

the bonds of the 3 phosphate groups attached to each nucleotide, when the bond is broken diphosphate is released allowing phophpdiester to bond

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21
Q

what is DNA wrapped around

A

histones in eukaryotes and arches and histone like proteins in bacteria

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22
Q

what relaxes a supercoiled DNA molecule

A

topoisomerase 2

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23
Q

what is another name for topoisomerase 2

A

DNA gyrase

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24
Q

what does helicase do

A

separats dna strands by breaking the hydrogen bonds between base pairs.

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25
what are replication forks
y shaped structures that are formed at the origin of replication allowing for bidirectional replication and a structure that looks like a bubble
26
what prevents single stranded DNA from rewinding into a double helix
the dna near the replication fork being coated with single stranded binding proteins
27
what direction is DNA pol 3 able to add nucleotides
only in the 5' to 3' directions
28
why can dna pol 3 only work in the 5'-3' directions
because DNA polymerase requires a free 3' -OH to add nucleotides too
29
can DNA pol 3 add a nucleotide if a 3' is not available
no
30
Describe th primer
an RNA sequence that provides free 3' ok end and is 5-10 nucleotides long and complementary to the parental or template dna
31
what is the primer synthesized from
RNA primase an RNA polymerase
32
what makes RNA polymerase different from DNA polymerase
RNA polymerase does not need a free 3' -oh group to synthesize an RNA molecule
33
what is the leading strand
the continuously synthesized DNA strand. the 5'-3' strand
34
what are Okazaki fragments
fragments of DNA replicated on the 3'-5' DNA strand (lagging strand)
35
how many primers does the lagging strand need
one for each Okazaki fragment
36
what is the sliding clamp
a protein that holds the DNA polymerase in place as it adds nucleotides to the lagging side
37
how does topoisomerase prevent overwinding of DNA at the replication fork
it causes temporary nicks in the dna helix and the resealing it
38
what happens to RNA primers during DNA replication
it is replaced by dna
39
how are RNA primers removed
the exonuclease activity of DNA polymerase 1 removes it and the gaps are filled in
40
what does DNA ligase do
fills the gaps seals the gaps between the dna that replaced RNA Primer and the previously synthesized dna
41
how are the DNA chromosomes separated from eachother
bacterial topoisomerase 4
42
what makes dna replication in bacteria from eukaryotes
DNA gyrase and topoisomerase 4
43
DNA pol 1 function
exonuclease activity removes RNA primer and replaces it with newly synthesized DNA
44
DNA pol 3 function
main enzyme that adds nucleotides in the 5' to 3' direction
45
helicase function
opens the DNA helix by breaking hydrogen bonds between the nitrogen bases
46
ligase function
seals the gaps between Okazaki fragments on the lagging strand to create one continuous dna strand
47
primase function
synthesizes RNA primers needed to start replication
48
single stranded binding proteins function
bind to single-stranded DNA to prevent hydrogen bonding between DNA stranded DNA
49
sliding clamp function
helps hold DNA pol 3 in place when nucleotides are being added
50
topoisomerase 2 (DNA gyrase) function
relazes supercoils chromosome to make DNA more accessible for the initiation of replication, helps relieve the tress on dna when unwinding, by causing breaks and the resealing dna
51
topoisomerase 4 function
introduces single stranded break into concatenated chromosomes to release them from each other, and then reseals the dna
52
how is dna replication in eukaryotes different than bacteria
it is slower, has multiple points of origin, uses RNase h instead of dna pol 1 for a primer removal, uses pol8 and pol e for strand elongation instead of dna pol 3
53
what is ribonuclease h
the enzyme that removes RNA primer in eukarotes instead of dna polymerase in Bactria
54
what are telomeres
the ends of linear chromosomes that consist of noncoding repetitive sequences
55
what do telomeres do
protect coding sequences from being lost as cells continue to divide
56
what does telomerase contain
a catalytic part and a built in RNA template
57
where does telomerase attach
to the end of the chromosome and complementary bases to the RNA template on the 3' end of the DNA strand
58
What is rolling circle replication
another process of dna replication used by bacteria, plasmids, bacteriophages and some eukaryote viruses
59
what happens in rolling circle replication
one strand of dna is nicked at the double stranded origin site dna polymerase binds to the 3' oh of the nicked trans and replicates unidirectionally look it up more it doesn't make sense
60
what is transcription
when information encoded within the dna sequence of one or ore genes is transcribed into a strand of dna
61
what is a transcription bubble
the partially unwound portion dna where rna synthesis is taking place
62
what is the antisense strand
the strand of dna that is acting as a template
63
what is the sense strand
the non template strand of dna that is almost identical to the rna
64
what is a critical difference between dna polymerase and rna polymerase
dna polymerase requires a 3' oh group requiring a primer where rna polymerase does not
65
what does rna polymerase comprise in ecoli
6 polypeptide subunits, 5 that compose the polymerase core enzyme responsible for adding rna nucleotides and a sigma factor
66
what does the sigma factor do
enables RNA polymerase to bind to a specific promoter for the trascription of genes
67
where does the initiation of transcription begin
the promotor
68
what is a promoter
a dna sequence onto which the transcription machinery binds and initiates transcription
69
what nucleotide is transcribed as the initiation site for transcription
the first 5' nucleotide in what's being copied
70
what is upstream?
the nucleotides preceding the initiation site
71
what is down stream
the nucleotides following the initiation site
72
when does elongation in transcription begin
when the sigma subunit dissociates from the polymerase allowing the core enzyme to synthesize rna complementary to dna
73
how does polymerase differ between prokaryotes and eukaryotes
eukaryotes use polymers 1, 2, 3 that are different from bacterial rna polymerase
74
what do polymers 1,2,3 transcribe
each a different subset of genes
75
what type of rna polymerase do arches contain
just one more closely related rna polymerase 2 than bacterial rna polymerase
76
what does monocistronic mean
eukaryotic mRNA that only encodes a single polypeptide
77
what does polycistronic mean
prokaryotic mRNA that encode s multipolypeptide
78

Microbiology (15 decks)

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