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Biology 243 > Topic 2B > Flashcards

Topic 2B Flashcards

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1
Q

ribosome

A

a complex structure of RNA and protein, bound to the cytosolic face of the RER in the cytoplasm, on which proteins are synthesized

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2
Q

what experiment demonstrated support for the hypothesis of an RNA intermediary that carries genetic info from DNA to ribosomes?

A

Brenner, Jacob, Meselson; T2 to infect E. Coli cells by hacking cellular machinery to produce viral proteins. Even though T2 NA never associated with bacterial ribosomes, the infected cells produce a burst of RNA shortly after infection and before viral proteins are made

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3
Q

what are three difference between DNA and RNA?

A

RNA has a ribose sugar (reactive hydroxyl group attached), uracil base replaces thymine in RNA, 5’ end is triphosphate, not monophosphate (DNA)

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4
Q

RNA transcript

A

the RNA sequence synthesized from a DNA template, complementary to template except has U instead of T

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5
Q

RNA polymerase

A

the enzyme that carries out polymerization of ribonucleoside triphosphates from a DNA template to produce an RNA transcript

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6
Q

nontemplate strand

A

the untranscribed partner of the template strand of DNA used in transcription

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7
Q

the RNA transcript and the DNA template strand are:

A

antiparallel

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8
Q

promoter

A

a regulatory region where RNA polymerase and associated proteins bind to the DNA duplex

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9
Q

TATA box

A

a DNA sequence present in many promoters in eukaryotes and archaeons that serves as a protein-binding site (promoter) for a key general transcription factor; 5’-TATAAA-3’

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10
Q

RNA polymerase moves along the TEMPLATE STRAND from:

A

3’ to 5’ direction, opposite to direction of synthesis of RNA transcript

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11
Q

terminator

A

a DNA sequence at which transcription stops and the transcript is released

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12
Q

different genes in the same double-stranded DNA can be transcribed from opposite strands, what determines which strand is transcribed?

A

the position of the promoter

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13
Q

housekeeping gene

A

a gene that is transcribed continually because its product is needed at all times and in all cells

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14
Q

most genes are transcribed…when?

A

only at certain times, under certain conditions, or in certain cell types

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15
Q

for genes that have regulated transcription, what does the regulation of transcription usually depend on?

A

whether the RNA polymerase and associated proteins are able to bind with the promoter

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16
Q

sigma factor

A

a protein that associates with RNA polymerase that facilitates its binding to specific promoters

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17
Q

in bacteria, promoter recognition is mediated by:

A

one protein-sigma factor

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18
Q

in eukaryotes, promoter recognition requires:

A

the combined action of at least six proteins-general transcription factors (bound at promoter), at least one type of transcriptional activator protein (bound at enhancer)

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19
Q

general transcription factors

A

a set of proteins that bind to the promoter of a gene whose combined action is necessary for transcription

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20
Q

transcriptional activator protein

A

a protein that binds to a sequence in DNA (enhancer) to enable transcription to begin

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21
Q

enhancer

A

a specific DNA sequence necessary for transcription

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22
Q

transcriptional activator proteins help control:

A

when and in which cells transcription of a gene will occur, is also essential for allowing transcription of any eukaryotic gene to begin

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23
Q

mediator complex

A

a complex of proteins that interacts with the Pol II complex and allows transcription to begin

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24
Q

recruitment of the mediator complex and RNA polymerase requires:

A

DNA to loop around to bring factors into close proximity, allowing transcription to proceed

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25
Pol II
the RNA polymerase complex responsible for transcription of protein-coding genes (eukaryotes)
26
initiation
the stage of translation in which methionine is established as the first amino acid in the new polypeptide chain
27
elongation
the process in protein translation in which successive amino acids are added one by one to the growing polypeptide chain
28
describe the RNA-DNA duplex
a bubble where DNA duplex strands are separated and RNA transcript is paired with template strand
29
the incoming ribonucleoside triphosphate is accepted by RNA polymerase only if:
it undergoes proper base pairing with the base in the template DNA strand (i.e. is complementary)
30
the energy released when the phosphate bond is broken is used to:
drive other chemical reactions (ex. attach incoming nucleotides to the 3' end of chain)
31
the two phosphates of the incoming ribonucleotide are released as:
pyrophosphate
32
cleavage of the pyrophosphate molecule makes the polymerization reaction:
irreversible
33
what does transcription require?
template DNA, a supply of ribonucleoside triphosphates, RNA polymerase, a large multi-protein complex in which transcription occurs
34
primary transcript
the initial RNA transcript that comes off the template DNA strand
35
messenger RNA (mRNA)
the RNA molecule that combines with a ribosome to direct protein synthesis; it carries the genetic "message" from the DNA to the ribosome
36
what is the relation between the primary transcript and mRNA in prokaryotes?
the primary transcript is the mRNA
37
what can transcription and translation occur at once? (i.e. why can primary transcript also act as mRNA?)
because there is no nuclear envelope to spatially separate transcription and translation; the two processes are coupled (connected in space and time)
38
in prokaryotes, the protein-coding genes often contain:
the genetic information for the synthesis of two or more different proteins
39
polycistronic mRNA
a single molecule of messenger RNA that is formed by the transcription of a group of functionally related genes located next to one another along bacterial DNA; codes for multiple proteins
40
what acts as a barrier between transcription and translation in eukaryotes?
the nuclear envelope; allows for RNA processing to occur
41
RNA processing
chemical modification that converts the primary transcript into finished mRNA, enabling the RNA molecule to be transported to the cytoplasm and recognized by the translational machinery
42
5' cap
the modification of the 5' end of the primary transcript by the addition of a special nucleotide attached in an unusual chemical linkage
43
what does the 5'cap bond link?
triphosphate bridge between the 5' carbons of both ribose sugars
44
why is the 5' cap essential for translation in eukaryotes?
the ribosome recognizes mRNA by its 5' cap, requires it to bind to ribosome
45
polyadenylation
the addition of a long string of consecutive A-bearing ribonucleotides to the 3' end of the primary transcript
46
poly (A) tail
the nucleotides added to the 3' end of the primary transcript by polyadenylation
47
5' cap and poly(A) tail help to:
stabilize RNA transcript, protect the two ends of the transcript
48
exon
a sequence that is left intact in mRNA after RNA splicing (regions of protein-coding sequence)
49
intron
a sequence that is excised from the primary transcript and degraded during RNA splicing (non-coding regions)
50
RNA splicing
the process of intron removal from the primary transcript
51
spliceosome
a complex of RNA and protein that catalyzes RNA splicing
52
RNA processing consists of which three principal types of chemical modification?
1. addition of 5' cap 2. polyadenylation 3. RNA splicing
53
lariat
a loop and tail of RNA formed after RNA splicing
54
outline the mechanism of RNA splicing:
spliceosome brings a specific sequence within intron into close proximity with 5' end of intron (5' splice site), cuts RNA and cleaved end forms a loop (lariat), cleaved 5' end attacks 3' splice site, cleaving bond that holds lariat and attaching ends of exons
55
alternative splicing
a process in which primary transcripts from the same gene can be spliced in different ways to yield different mRNAs and therefore different protein products
56
what does the presence of multiple introns allow?
alternative splicing
57
not all primary transcripts are processed into RNA, these transcripts are produced by:
RNA polymerases other than Pol II, allows them to undergo different types of RNA processing
58
ribosomal RNA (rRNA)
noncoding RNA found in all ribosomes that aid in translation
59
transfer RNA (tRNA)
noncoding RNA that carries individual amino acids for use in translation
60
nucleolus
a distinct, dense, non-membrane-bound spherical structure within the nucleus that contains the genes and transcripts for ribosomal RNA
61
where are the genes and transcripts for ribosomal RNA concentrated in eukaryotes?
in the nucleolus
62
small nuclear RNA (snRNA)
noncoding RNA found in eukaryotes and involved in splicing, polyadenylation, and other processes in the body
63
what are two types of regulatory RNA transcripts?
miRNA and siRNA
64
microRNA (miRNA)
small, regulatory RNA molecules that can cleave or destabilize RNA or inhibit its translation
65
small interfering RNA (siRNA)
a type of small double-stranded regulatory RNA that becomes part of a complex able to cleave and destroy single-stranded RNA with a complementary sequence
66
what are the most abundant type of RNA transcripts in mammalian cells and why?
rRNA and tRNA, because they are needed in large amounts to synthesize the proteins encoded in mRNA

Biology 243 (15 decks)

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