Transcription and Translation Flashcards
Where does transcription occur in prokaryotes and eukaryotes?
Prokaryotes - cytoplasm
Eukaryotes - nucleus
Where does RNA polymerase bind to start initiation?
RNA polymerase binds to the promoter sight and unwinds DNA
Describe elongation
RNA polymerase moves along the DNA stand 5’ to 3’. As DNA and RNA transcript exit the enzyme, RNA is removed from the template and DNA rewinds
What is the DNA sequence that is the recognition start site
TATA box
What is a transcription initiation complex?
where TFs bind to the DNA to attract RNA polymerase and create a complex to make RNA
Describe a) 5’ cap b) 3’ tail
a) 5’ cap - added to mRNA while still being transcribed. It is a genetically modified GTP molecule and its is important as it facilitates binding of mRNA to enzyme for translation and it protects against digestion by ribonucleases
b) added immediately after mRNA transcript is released. Is composed of 100-300 A nucleotides and is important as it exports mRNA from the nucleus to the cytoplasm and increases stability
What is an intron?
a length of non-coding DNA
BUT they are transcribed
What is splicing?
The removal of introns from mRNA
What is splicing performed by?
snRNPs - small nuclear ribonucleoproteins
Where are introns removed?
While the mRNA is still inside the nucleus
What is on the end of exons that bond once the intron is removed?
3’ OH and 5’ phosphate
Where does the ribosome attach in transcription in a) prokaryotes b) eukaryotes
a) a recognition site
b) 5’ cap
What is the start codon in eukaryotes?
AUG (methionine)
Describe the attachment of the small and large units of ribosomes
The small unit attaches and moves along until it find the start codon. Here the tRNA with the anticodon for AUG binds and all 3 components for the initiation complex. The the large unit binds to this
What are the 3 sites in the large ribosome?
A - anticodon
P - polypeptide
E - exit
