HYS 7.2 Transcription

Question 1

mRNA

Answer 1

messenger mRNA
carries message in DNA encoded to ribosomes

Question 2

transcription

Answer 2

DNA –> mRNA
process by which we make a polymer of RNA

Question 3

RNA polymerase and 3 stages

Answer 3

initation
elongation
termination

Question 4

promoters in prokaryotes and eukaryotes

Answer 4

both have TATA rich sequence upstream of start site

TFs bind to promoter to signal RNA polymerase
TATA box (eukaryotes) 25-35 bp upstream helps recruit RNA polymerase

prokaryotes also a similar region of TATA called pribnow box or minus 10 sequence bc its 10 bp upstream

Question 5

what happens in initation of transcription?

Answer 5

initiation: start
RNA polymerase binds advance of start site of transcription
promoter - upstream area

TFs bind to promoter to signal RNA polymerase
TATA box (eukaryotes) 25-35 bp upstream helps recruit RNA polymerase
prokaryotes also a similar region of TATA called pribnow box or minus 10 sequence bc its 10 bp upstream

helicases unwinds
RNA polymerase binds promoter and moves forward
reads first base and matches it with complementary base
G—> C (compliment)

Question 6

what happens in elongation of transcription?

Answer 6

creates complementary bases and catalyzes phosphodiester bond

sense (coding): when read it 5’3’ makes the correct protein
* carries code for gene

antisense (template): complementary strand bc it has the opposite (compliment)
* gets read and transcribed
replaces T with U

Question 7

what happens in termination of transcription in prokaryotes?

Answer 7

prokaryotes
1. rho dependent
* * rho protein binds to RNA and increases sterics which pulls RNA way from RNA polymerase
* RNA is ready to me translated
* DNA is ligated
2. rho independent
* GC sequence in RNA causes binding and loop causing steric strain which pulls RNA away from RNA polymerase

Question 8

do eukaryotes or prokaryotes have a nucleus

Answer 8

prokaryotes have no nucleus and transcribe genes directly in cytoplasm
fast!

eukaryotes have a nucleus which means they can further process RNA before sent out of nucleus and into cytoplasm for translation

Question 9

what is post-transcriptional processing and does it occur in prokaryotes or eukaryotes?

Answer 9

modifications after transcription of RNA in nucleus before mRNA transcript goes to cytosol for translation

only in eukaryotes

5’ methylguanosine cap (guanine nucleotide attached backwards) prevents mRNA degredation

cells use exonucleases to chew up and degrade nucleic messages to remove unusual DNA structues arising from fork problems, repair DNA

3 ‘ poly AAA tail prevents degredation which delays exonucleases from reaching important code from being eaten

longer poly AA tail means message lasts longer

excise introns (splicing)

Question 10

what does the 3’ poly AA tail do?

Answer 10

3 ‘ poly AAA tail prevents degredation which delays exonucleases from reaching important code from being eaten

longer poly AA tail means message lasts longer

shorter poly AA tail means message lasts shorter

Question 11

tRNA and rRNA

Answer 11

rRNA makes up ribosome for translation

tRNA in translation