lecture 24 Flashcards
What are the steps for gene-to-protein expression
Transcription
Translation
Post-translational modifications
Genetic mutations
What is the flow of genetic information?
DNA-> Transcription->RNA-> Translation-> Protein
Where does transcription take place in a prokaryotic cell?
cytoplasm
Where does translation take place in a prokaryotic cell?
cytoplasm
Where does transcription take place in a eukaryotic cell?
nucleus
Where does translation take place in eukaryotic cells?
cytoplasm
Where does RNA processing take place in eukaryotic cells?
nucleus
What are the forms that DNA goes through before becoming a polypeptide in a prokaryotic cell?
RNA, mRNA, ribosome-> polypeptide
What are the forms that DNA goes through before becoming a polypeptide in a eukaryotic cell?
DNA, Pre-mRNA, mRNA, ribosome-> polypeptide
What is the difference between gene expression in a prokaryotic cell vs eukaryotic cell?
prokaryotic cells dont process mRNA (no introns)
In eukaryotic cells, mRNA is processed (introns are present and these are spices out from pre-mRNA
What is a codon?
three nucleotide bases, eg GAA
How many possibilities for codons are there?
64 ; 4^3
What does redundancy mean in mRNA and what is the exception?
Codes for all 20 amino acids
multiple codons for one amino acid
exception: AUG for Methionine and UGG for Tryptophan
True/False: all mRNA have unambiguous codes?
true; no 2 amino acids have the same code
Is mRNA codes universal?
Yes
What is a promoter?
DNA sequence to which RNA polymerase binds to
What is RNA polymerase?
An enzyme that initiates and drives RNA synthesis
What is a start point?
where the transcription starts
What is a transcription unit?
DNA sequence (gene) coding for RNA molecule + termination sequence
What happens during the initiation of transcription (step 1)?
-RNA polymerase pries the DNA strands apart and catalyzes joining of RNA nucleotides using the Template strand of DNA
-the mRNA mase is complementary to the DNA template strand
-RNA polymerase does not need any primer (unlike DNA polymerase)
-DNA synthesis follows the same base-pairing rules as DNA, except that uracil substitutes for thymine
What happens during the elongation of RNA transcript (step2)?
-as RNA polymerase moves along the DNA, it untwists the double helix, 10 to 20 bases at a time
-transcription progresses at a rate of 40 nucleotides per second in eukaryotes
-nucleotides are added to the 3’ end of the growing RNA molecule
-a gene can be transcribes simultaneously be several RNA polymerases (multiple copies of mRNA are mase from the same template
What happens during the termination of transcription (step 3)?
-in bacteria, the polymerase stops transcription at the end of the terminator and the mRNA can be translated without further modification
-the mechanisms of termination are different in bacteria and eukaryotes
-in eukaryotes, RNA polymerase II transcribes past the terminator sequence
What occurs in transcription initiation in bacteria?
-sigma factor recognizes specific DNA sequences at -10 Region and -35 region
-other RNA polymerase subunits bind to sigma
-sigma remains while the others begin trasncriptions
What is the function of the sigma factor?
recognizes specific DNA sequence at -10 Region and -35 region
What is the role of transcription factors in eukaryotic transcription?
bind the promoter sequence
What do activators do in eukaryotic transcription?
bind to the enhancer sequences (sometimes far away)
What do Co-activators do in eukaryotic transcription?
bring everyone together including RNA polymerase
What does RNA polymerase do in eukaryotic transcription?
takes off by itself
What do bacterial genes not have?
introns= no RNA processing
What is the function of RNA processing?
addition of the 5’ CAP and poly-a-tail
