Transcription

Question 1

transcription 3 basic phases

Answer 1

-initiation
-transcription
-termination

Question 2

in order for DNA to carry out functions what must it do

Answer 2

-be converted to RNA via transcription

Question 3

promoters

Answer 3

-DNA sequences
-Guides transcription initiation
-resides upstram of henes
-in conclusion: DNA sequenxes bound by factors that promote transcriptional initiation

Question 4

sigma factors

Answer 4

-binding of sigma factors to the promotor region (along iwth regulatory proteins) dictates whther a sequence acts as a promoteor and if promotor is active

Question 5

sigma factors in transcription initation

Answer 5

-a special subunit of RNA polymerase called sigma factor binds DNA as an essential step in initiating transcription
-Bacteria encode various sigma factors that are produced under different conditions
-

Question 6

RpoD

Answer 6

-most commonly used
-recognizes two seuqences upstram of the transcriptional tartssite
-recognizes sequences at -36 and - 10 (pribnow box) upstream of the +1 site

Question 7

the promotor region is where compared to the gene

Answer 7

upstream

Question 8

RNA polymerase

Answer 8

bind to DNA template and makes an RNA copy of one of two strans
-Copied strand = coding strand (promotor dictates), othr strand = template strand
-builds RNAs 5’-3’
-

Question 9

core enzyme

Answer 9

-bacteria
-5 subunits
-alpha (2 copies) beta, beta prime, omega,
-holoenzyme (type of core enzyme) also includes sima subunit
-core enzyme unwinds DNA to expose template and form transcription bubble
-Uses NTP as substrates and template strand as gyude

Question 10

termination of transcription

Answer 10

-RNAP dissociates from DNA, stops making RNA and releases transcript

Question 11

intrinsic (rho independent) terminators

Answer 11

-RNA forms hair pin strictire followed by a string of U reisdues
-U resideus act as a pause signal for RNAP and formation of hair pin fors RNAP off template

Question 12

Rho dependent terminators

Answer 12

-Protein called Rho binds RNA as it is being transcribed and causes RNA polymerase to dissociate after it encounters certain sequences

Question 13

3 major classes of RNAs

Answer 13

-mRNA - converted to protein via translation
-tRNA - functional RNAs used in translation process
-rRNA - functional RNA used in translation process

Question 14

what is the majority of RNA

Answer 14

-rRNA and tRNA

Question 15

mRNA contains

Answer 15

-both ORFs and UTRs
-ORFS are translated to protein
-UTR are part of the mRNA transcript that are not translated into protein

Question 16

polycistronic

Answer 16

-mRNAs that encode multiple ORFs are polycistronic
-Genes are arranges in an operon
-Genes on an operon are cotranscribed

Question 17

In a simple mRNA encoding a single open reading frame there is

Answer 17

-5’UTR - everything from first transcribed residue through the start codon of gene, contains ribsome binding site
-ORF - Start codon through stop codon
-3’UTR - everything from stop codon of gene through the final transcribed reisdue. often contains transcriptional terminator sequences

Question 18

how is transcription different in eukaryotes

Answer 18

-eukaryotes have 3 RNA polymerases. RNA polymerase II produces mRNA
-eukaryotic RNA polymerases are more complex (12+)
-eukaryotic RNA polymerases required transciption factos to recognize promotors (bind to DNA sequqences adn recruit RNA polymerase)
-Eukaryoties do not use operans each genes has its own promotor
-eukaryotic primary mRNA transcripts contain protein coding exons and non coding introns, mRNA are processed to remove introns
-Eukaryotic have polyA tails addes and capped at 5’ end
-eukaryotic mRNA are trasncribed and spliced in nuclues and translated in cytoplasm

Question 19

overview of transcript processing and transport om eukaryotic cells

Answer 19

Question 20

transciption in archaea

Answer 20

-core aspects of archeal transcription are very. similar to eukaryotic transcription
-the archael RNA polymerase II from eukaryotes and has 11-13 subunits
-is also recruited to promotors using TF- many of which are related to eukaryotic proteins
-archaea also uses TATA boxes and TF that bind these elements and recruit RNA polymerase

Question 21

similaritys of arahcea and bacteria transcription

Answer 21

-no 5’ cap
-no polyA taile
-mRNAs do not have introns and are are not spliced
-no nucleus transcription and translation often coupled like in bacteria
-archeaea use opens - multiple henes encoded by one RNA
-basically a less complex version of eukaryotic transcription