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Med 103 > transcription > Flashcards

transcription Flashcards

1
Q

give 3 similarities between DNA replication and transcription

A
  1. Both processes use DNA as the template.
  2. Both synthesis directions are from 5´ to 3´.
  3. Phosphodiester bonds are formed in both cases
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2
Q

give 5 differences between DNA replication and protein synthesis

A
  1. double/single strands
  2. substrates- dNTP/NTP
  3. DNA polymerase/RNA polymerase
  4. product- dsDNA/ssRNA
  5. thymine/uracil
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3
Q

what are structural genes

A

DNA regions that can be transcribed into RNA

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4
Q

what is the antisense strand

A

template strand

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5
Q

what is the sense strand

A

coding strand i.e. the strand whose base sequence specifies the amino acid sequence of the encoded protein

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6
Q

what is it called when transcription direction on different strands is opposite

A

asymmetric transcription

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7
Q

what is the function of the α, β, β’, and σ subunits in bacterial RNA polymerase

A

α- Determine the DNA to be transcribed
β- Catalyze polymerization
β’- Bind & open DNA template
σ- Bind & open DNA template

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8
Q

what does Rifampicin do

A

therapeutic drug for tuberculosis treatment, can bind specifically to the beta subunit of RNA-pol, and inhibit the RNA synthesis

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9
Q

what does one operon include

A

several structural genes and upstream regulatory sequences (or regulatory regions)

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10
Q

what is the -35 region of TTGACA sequence

A

recognition site and the binding site of RNA-pol

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11
Q

what is -10 region of TATAAT (pribnow box)

A

region at which a stable complex of DNA and RNA-pol is formed

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12
Q

what is the consensus sequence

A

a sequence of DNA having similar structure and function in different organisms

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13
Q

what do the RNA polymerase holoenzyme and promoter form

A

closed promoter complex

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14
Q

how does the open promoter complex form

A

when polymerase unwinds about 17 pairs

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15
Q

what is a holoenzyme

A

the core enzyme saturated with sigma factor

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16
Q

in bacteria what sequence does the RNA pol recognize and then after slides to

A

TTGACA region and TATAAT region

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17
Q

what is the first nucleotide on RNA transcript

A

purine triphosphate

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18
Q

when does the sigma subunit fall of from the RNA pol

A

once the first 3 prime,5 prime phosphodiester bond is formed

19
Q

where are the free NTPs added in bacteria

A

sequentially to the 3 prime -OH of the nascent RNA strand

20
Q

what forms the transcription bubble in bacteria

A

RNA-pol, DNA segment (~40nt) and the nascent RNA

21
Q

what
a) hybridizes with the DNA template
b) extends out the transcription bubble as the synthesis is processing
(in bacteria)

A

a) 3 prime segment

b) 5 prime segment

22
Q

what do RNA polymerases I, II and III transcribe respectively

A

rRNA, mRNA and tRNA genes, respectively

23
Q

what transcribes other RNAs as well

A

RNA polymerase III

24
Q

what are cis and trans regulatory products

A
  • cis-regulatory elements are present on the same molecule of DNA as the gene they regulate (often binding sites for one or more transacting factors)
  • trans-regulatory elements can regulate genes distant from the gene from which they were transcribed
25
Q

what are the cis- acting elements

A
  • Promotor

* Enhancer

26
Q

what is a region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur

A

enhancer

27
Q

enhancers are only in eukaryotes, true or false

A

false, they are in both eukaryotes and prokaryotes

28
Q

what are the three cis acting elements that help

polymerase II initiate transcription in eukaryotes

A

TATA box (determine the starting point of transcription by
facilitating the unwinding of the helix)
CAAT box
GC box

29
Q

what are the functions of the transacting elements

A

1) interact with cisacting elements to control transcription initiation
2) facilitate binding to the DNA template

30
Q

what do most transcription factors do during elongation

A

Most of the TFs fall off from from the pre-initiation complex

31
Q

what is the termination sequence in eukaryotes

A

AATAAA followed by GT repeats

32
Q

what is the primary transcript also called

A

heteronuclear RNA

33
Q

what are the postmodifications that occur on RNA

A
  • Capping at the 5- end
  • Tailing at the 3- end
  • mRNA splicing
  • RNA edition
34
Q

what is the 5 prime cap

A

7-methylguanosine cap which is a modified guanine (G)

nucleotide

35
Q

what enzyme catalyzes the additions of 200 A nucleotides to the 3′ end of the just cleaved pre-mRNA

A

Poly (A) Polymerase (PAP)

36
Q

when cleaving, what does the endonuclease-containing protein complex bind to

A

AAUAAA sequence upstream of the cleavage site and to a GU-rich sequence downstream of the cut site

37
Q

what does the spliceosome do

A

spliceosome removes introns from a transcribed pre-mRNA

38
Q

what is RNA editing

A

may include the insertion, deletion, and base substitution of nucleotides within the RNA molecule (rare)

39
Q

what are the four rRNAs in eukaryotes first transcribed as

A

two long precursor molecules

40
Q

why are some of the bases of pre-rRNAs methylated

A

for added stability

41
Q

all of ribosome’s RNA is structural, true or false

A

False. Some of a ribosome’s RNA molecules are purely structural, whereas others have catalytic or binding activities

42
Q

what is the first step in processing tRNA

A

digestion of the RNA to release individual pre-tRNAs

43
Q

what are the five steps in converting the pre-tRNA to a mature tRNA

A

(1) The 5′ end of the pre-tRNA, called the 5′ leader sequence, is cleaved off
(2) The 3′ end of the pre-tRNA is cleaved off
(3) a CCA sequence of nucleotides is added to the 3′end of the pre-tRNA
(4) Multiple nucleotides in the pre-tRNA are chemically
modified, altering their nitrogen bases
(5) introns that have to be spliced out

44
Q

what are the most common modifications of tRNA nucleotides

A

conversion of adenine (A) to pseudouridine (ψ), the conversion of adenine to inosine (I), and the conversion of uridine to dihydrouridine (D)

Med 103 (13 decks)

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