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Biology 243 > Topic 2B > Flashcards

Topic 2B Flashcards

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
Q

Pol II

A

the RNA polymerase complex responsible for transcription of protein-coding genes (eukaryotes)

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26
Q

initiation

A

the stage of translation in which methionine is established as the first amino acid in the new polypeptide chain

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27
Q

elongation

A

the process in protein translation in which successive amino acids are added one by one to the growing polypeptide chain

28
Q

describe the RNA-DNA duplex

A

a bubble where DNA duplex strands are separated and RNA transcript is paired with template strand

29
Q

the incoming ribonucleoside triphosphate is accepted by RNA polymerase only if:

A

it undergoes proper base pairing with the base in the template DNA strand (i.e. is complementary)

30
Q

the energy released when the phosphate bond is broken is used to:

A

drive other chemical reactions (ex. attach incoming nucleotides to the 3’ end of chain)

31
Q

the two phosphates of the incoming ribonucleotide are released as:

A

pyrophosphate

32
Q

cleavage of the pyrophosphate molecule makes the polymerization reaction:

A

irreversible

33
Q

what does transcription require?

A

template DNA, a supply of ribonucleoside triphosphates, RNA polymerase, a large multi-protein complex in which transcription occurs

34
Q

primary transcript

A

the initial RNA transcript that comes off the template DNA strand

35
Q

messenger RNA (mRNA)

A

the RNA molecule that combines with a ribosome to direct protein synthesis; it carries the genetic “message” from the DNA to the ribosome

36
Q

what is the relation between the primary transcript and mRNA in prokaryotes?

A

the primary transcript is the mRNA

37
Q

what can transcription and translation occur at once? (i.e. why can primary transcript also act as mRNA?)

A

because there is no nuclear envelope to spatially separate transcription and translation; the two processes are coupled (connected in space and time)

38
Q

in prokaryotes, the protein-coding genes often contain:

A

the genetic information for the synthesis of two or more different proteins

39
Q

polycistronic mRNA

A

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
Q

what acts as a barrier between transcription and translation in eukaryotes?

A

the nuclear envelope; allows for RNA processing to occur

41
Q

RNA processing

A

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
Q

5’ cap

A

the modification of the 5’ end of the primary transcript by the addition of a special nucleotide attached in an unusual chemical linkage

43
Q

what does the 5’cap bond link?

A

triphosphate bridge between the 5’ carbons of both ribose sugars

44
Q

why is the 5’ cap essential for translation in eukaryotes?

A

the ribosome recognizes mRNA by its 5’ cap, requires it to bind to ribosome

45
Q

polyadenylation

A

the addition of a long string of consecutive A-bearing ribonucleotides to the 3’ end of the primary transcript

46
Q

poly (A) tail

A

the nucleotides added to the 3’ end of the primary transcript by polyadenylation

47
Q

5’ cap and poly(A) tail help to:

A

stabilize RNA transcript, protect the two ends of the transcript

48
Q

exon

A

a sequence that is left intact in mRNA after RNA splicing (regions of protein-coding sequence)

49
Q

intron

A

a sequence that is excised from the primary transcript and degraded during RNA splicing (non-coding regions)

50
Q

RNA splicing

A

the process of intron removal from the primary transcript

51
Q

spliceosome

A

a complex of RNA and protein that catalyzes RNA splicing

52
Q

RNA processing consists of which three principal types of chemical modification?

A
  1. addition of 5’ cap
  2. polyadenylation
  3. RNA splicing
53
Q

lariat

A

a loop and tail of RNA formed after RNA splicing

54
Q

outline the mechanism of RNA splicing:

A

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
Q

alternative splicing

A

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
Q

what does the presence of multiple introns allow?

A

alternative splicing

57
Q

not all primary transcripts are processed into RNA, these transcripts are produced by:

A

RNA polymerases other than Pol II, allows them to undergo different types of RNA processing

58
Q

ribosomal RNA (rRNA)

A

noncoding RNA found in all ribosomes that aid in translation

59
Q

transfer RNA (tRNA)

A

noncoding RNA that carries individual amino acids for use in translation

60
Q

nucleolus

A

a distinct, dense, non-membrane-bound spherical structure within the nucleus that contains the genes and transcripts for ribosomal RNA

61
Q

where are the genes and transcripts for ribosomal RNA concentrated in eukaryotes?

A

in the nucleolus

62
Q

small nuclear RNA (snRNA)

A

noncoding RNA found in eukaryotes and involved in splicing, polyadenylation, and other processes in the body

63
Q

what are two types of regulatory RNA transcripts?

A

miRNA and siRNA

64
Q

microRNA (miRNA)

A

small, regulatory RNA molecules that can cleave or destabilize RNA or inhibit its translation

65
Q

small interfering RNA (siRNA)

A

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
Q

what are the most abundant type of RNA transcripts in mammalian cells and why?

A

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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