W7L3 - Gene Expression I Flashcards
(16 cards)
Explain why DNA has to be reliable/stable
it needs to store genetic information that has to be passed down to other cellular processes in the body
Why is RNA not stable
RNA is only a copy and is later discarded
What occurs in initiation of transcription
RNA polymerase binds to the promoter region. DNA strands unwind. RNA synthesis is initiated by the RNA polymerase
What is the difference between RNA and DNA replication
No helicase required and RNA nucleotides are created
What does RNA polymerase do
Makes a complementary RNA copy of DNA called mRNA
What happens in transcription (elongation)
RNA polymerase moves upstream unwind DNA and elongate the RNA transcript (mRNA), once transcribed DNA reforms double helix
What happens in termination (transcription)
RNA polymerase transcribes a terminator sequence signalling end of gene, RNA polymerase detaches from DNA
Why is the promoter filled with AT
AT has 2H bonds easier to break apart
What type of proteins mediate the initiation of transcription
transcription factors > direct RNA polymerase to that region which is an additional control mechanism
What is the cap and tail in mRNA
protect genes made up of guanine nucleotide added to the 5 end and poly a-tail 50-250 adenine nucleotides
How does cap and tail protect mRNA from viruses
Prevent viruses injecting RNA in our RNA, which they use our cellular processes to turn into viral proteins
What is 5’ cap made of up
3-phosphate groups
What is present in the poly-A tail
50-250 adenine nucleotides are added to the 3’ end
What occurs in splicing
Introns are removed before leaving nucleus and exons are spliced out to produce different proteins
How does transcription/translation occur in prokaryotes
Prokaryotes have no nucleus, as the mRNA is directly translated into proteins
How does transcription/translation occur in eukaryotes
Since eukaryotes have a nucleus, mRNA is formed as pre-mRNA in the nucleus, modified, then exported into the cytoplasm
