Transcription Flashcards
where does transcription take place
euk: nucleus
pro: cytoplasm
what occurs in transcription
the 3 types of RNA are made
what are the 3 types of rna and what do they do
mRNA: carries message from dna that will be translated to become a polypeptide chain
tRNA: brings a.a from cytoplasm and has an anti codon that will create a polypep chain thru ribosome
rRNA: parts of ribosome
initiation phase in transcription
- begins at PROMOTER
- RNA POLYMERASE binds to promoter
- 2 promoter seq for extra security
elongation phase in transcription
- rna polymerase and other proteins create a TRANSCRIPTION COMPLEX
- transcription complex identifies the correct strand (template strand) and begins unwinding/unzipping and begins copying DNA to make RNA in 5’ –> 3’ direction
- rna poly breaks h-bonds and adds complementary bases (U replaced with T)
- DNA naturally rebinds as rna poly moves across
termination phase in transcription
rna poly reaches terminator -> detaches and rna leaves to go to transcription
mRNA processing
- 5’ cap and Poly-A tail added to rna
- spliceosomes snip introns out, leaving just exons
- mrna is sent to ER for translation
what is the purpose of the 5’ cap
helps mRNA combine with ribosome
poly-a tail purpose
allows mrna to be reused to make same protein, will slowly erode each time its reused
where does translation occur
cyctoplasm
explain the events of translation
- mRNA 5’ end binds to small ribosomal subunit
- tRNA binds to p-site with start codon, signaling the rest of ribosome to be made
- another complementary tRNA binds its anticodon to the exposed codon at a-site
- ribosome forms peptide bond between a.a in p-site and a-site
- ribosome shifts tRNA along as it moves across the mRNA strand
- A-P-E process continues until ribosome reaches STOP codon –> ribosome dismantles
