RNA transcription #13

Question 1

why do we need mRNA? Why not directly go from DNA to proteins?

Answer 1

~it allows the cell to separate info. storage from info. utilization
~it allows a greatly amplified synthetic output

Question 2

who discovered transcription

Answer 2

roger david kornberg

Question 3

what are the 4 differences between eukaryotic and prokaryotic mRNA

Answer 3

~prokaryotic mRNA is polycisternic while eukayotes’ is monocistronic (meaning a single mRNA can code for only one protein so it contains only one site of initiation/termination)
~in bacteria translation of the mRNA starts while it is still being transcribed
~bacterial mRNA undergoes very few post transcriptional changes
~life span of bacterial mRNA is very short

Question 4

the first level of gene expression regulation is?

Answer 4

transcription

Question 5

transcription

Answer 5

is a polymerization reaction in which single ribonucleotides are linked to build a polyribonucleotide strand complementary to a DNA strand

Question 6

what does the transcription reaction require

Answer 6

~RNA polymerase
~DNA template
~Mg2+ or Mn2+
~the 4 ribonucleotide triphosphates

Question 7

what are the 3 steps of transcription

Answer 7

initation, elongation, termination

Question 8

an RNA polymerase that moves from left to right uses which strand as a template?

Answer 8

the botton one

Question 9

an RNA polymerase that moves from right to left uses which strand as a template?

Answer 9

the top one

Question 10

RNA polymerase produces?

Answer 10

mRNA

Question 11

the region where the RNA polymerase binds is called the

Answer 11

promoter

Question 12

the spacing between the 2 consensus sequences (region 10 and 35) locates?

Answer 12

the 2 sequences on the same side of the double helix facilitating its interaction with the RNA pol subunit that binds DNA

Question 13

what is a consensus sequence

Answer 13

it is the calculated order of most frequent residues found at each position in a sequence alignment

Question 14

what is the function and position of UP element?

Answer 14

it is found in strong promoter regions, it is an additional DNA element and it helps RNA pol binding . it is located on the outer side of region 35

Question 15

how does RNA pol bind to DNA

Answer 15

the C-terminal domain recognizes the UP element, the sigma subunit recognizes the -35 and -10 elements

Question 16

what are the 4 steps of RNA transcription in prokaryotes

Answer 16

~ RNA polymerase binds the promoter
~ The sigma factor dissociates from RNA polymerase
~ RNA polymerase transcribes RNA copying the DNA template
~ A new RNA pol molecule binds the promoter

Question 17

are all eukaryotic promoters the same?

Answer 17

no

Question 18

what is the core promoter

Answer 18

the site where the RNA pol binds

Question 19

As the affinity for RNA pol and the promoter are very low, how are they bound together?

Answer 19

~constitutive transcription factors

~ specific transcription factors (act on a few genes in a regulated way)

Question 20

how is initial contact between the promoter and RNA pol II made?

Answer 20

through the GTF TFIID which is made of the TATA bonding protein and the 12 TBP

Question 21

the TATA box binding protein is?

Answer 21

is a subunit of the GTF TFIID, it is responsible fo the recognition and binding to the TATA-box.

Question 22

after the RNA pol II has bound, then what?

Answer 22

it first starts doing abortive transcriptions, then once its C-Terminal tail is phosphorylated most of the GTF are released and the RNA polII can leave the promoter area (promoter clearance) starting the elongation process of transcription

Question 23

what are the 3 possible functions of the elongation factors?

Answer 23

~suppressing/pausing RNA pol II
~prevent arrest - stop elongation
~modify chromatin - to assist elongation