RNA and Genetic Code Flashcards
In what direction does the ribosome read the mRNA transcript, and in what direction does it synthesize the protein?
ribosome reads mRNA 5’ –> 3’
ribosome translates protein N terminal –> C terminal
what is the function of aminoacyl-tRNA synthetase?
charges 3’ end of tRNAs with proper amino acid
What is the CCA nucleotide sequence?
it is the terminal 3’ sequence on tRNA where amino acids bind (5’-CCA-3’)
How many phosphoanhydride bonds from ATP is required for tRNA charging?
2 ATP bonds
aminoacyl-tRNA synthetase converts ATP to AMP+PPi
What are the three stop codons?
UAG
UGA
UAA
What is the RNAP II binding site in the DNA promoter region, in eukaryotes?
TATA box
contains high amount of T’s and A’s
What are the difference functions of RNAP I, RNAP II, and RNAP III, in eukaryotes?
RNAP I - synthesizes rRNA in nucleolus
RNAP II - synthesizes hnRNA and snRNA
RNAP III - synthesizes tRNA and some rRNA
what are snRNAs and snRNPs involved in?
splicing, forming the spliceosome
what is a lariat?
the lasso-shaped structure that intron forms after it is spliced out
what’s the size and components of the large ribosomal subunit in prokaryotes and eukaryotes?
large ribosomal subunit
prokaryotes: 50 - 5S + 23S
eukaryotes: 60 - 5S + 28S + 5.8S
what’s the size and components of the small ribosomal subunit in prokaryotes and eukaryotes?
small ribosomal subunit
prokaryotes: 30 - 16S
eukaryotes: 40 - 18S
what’s the size of the ribosome in eukaryotes and prokaryotes?
ribosome
prokaryotes: 70S
eukaryotes: 80S
What is the rRNA that RNAP III synthesizes in eukaryotes?
5S, located in the large ribosomal subunit
what is the shine-delgarno sequence?
in prokaryotes, it is the binding site for the small ribosomal subunit in the 5’ UTR of mRNA
what on mRNA does the small ribosomal subunit bind to in eukaryotes?
5’ cap
what is the function of peptidyl transferase?
an enzyme on large ribosomal subunit that uses GTP to form peptide bond
it transfers peptide chain to tRNA in P site to tRNA in A site.
what’s the role of initiation factors?
help large ribosomal subunit bind to small ribosomal subunit
what’s the role of elongation factors?
recruits aminoacyl-tRNAs and GTP, remove GDP
Peptides that must be secreted from the cell contain a signal sequence that sends them where?
peptides for secretion contain a signal sequence that causes ribosome to attach to ER –> protein is trasnalted into lumen of rough ER –> protein goes to golgi apparatus –> protein is secreted through exocytosis
How does termination of translation occur?
- RF (release factor) binds to stop codon in A site.
- water is added to peptide chain
- peptide is hydrolyzed from tRNA by termination factors and peptidyl transferease
what is prenylation?
addition of lipid groups to a protein, often to membrane-bound proteins
According to the Jacob-Monod Model, what is the structure of an operon? (hint: prokaryotes)
From right to left (3’ –> 5’)
- structural gene
- operator site: binding site for repressor protein
- promoter site: binding site for RNAP
- regulate gene: codes for repressor protein
what is an operon? (hint: prokaryotes)
a cluster of genes that are transcribed together as one mRNA (ex. trp operon - 5 enzymes involves in Trp synthesis)
What’s the difference between an inducible system and a repressible system?
an inducible system is normally “off”. turned “on” by an inducer. repressor is active on operator.
a repressible system is normally “on”. turned “off” when repressor binds to a corepressor. unbound repressor is inactive on operator.
