RNA molecules Flashcards
3 primary regions of mRNA
5’ untranslated region, protein coding region, 3’ untranslated region,
What does the 5’ UTR do?
consensus sequence, in bacteria Shine-Dalgarno sequence is the ribosome binding site
what does the 3’ UTR do?
affects stability of mRNA and helps regulate translation
pre-mRNA processing
only in eukaryotes. addition of 5’ cap, 3’ cleavage and poly-A tail added, and introns are spliced out.
5’ cap functions
Facilitates binding of ribosome to 5′ end of mRNA, increases mRNA stability, enhances RNA splicing
poly-A tail functions
Increases stability of mRNA, facilitates binding of ribosome to mRNA, signals mRNA can leave nucleus
RNA splicing functions
Removes noncoding introns from pre-mRNA, facilitates export of mRNA to cytoplasm, allows for multiple proteins to be produced through alternative splicing
RNA splicing process
spliceosome cuts the 5’ splice site which then attaches to the branch point (within the intron). the 3’ splice site is cut and a lariat is released. the exons are spliced together
spliceosome
consist of a complex of many snRNPs ( small nuclear RNA)
Alternative splicing
Removing different combinations of introns and exons.
multiple 3’ cleavage sites
cleavage may be at multiple 3’ sites, resulting in mRNA of different lengths depending on the splice site.
Alternative Processing Pathways
includes alternative splicing and multiple 3’ cleavage sites. Both can exist in the same pre-mRNA transcript. Important for making more products from less genes
rRNA
large (joins amino acids) and small (reads the mRNA) subunits form ribosome.
tRNA arms
acceptor arm (not hairpin) where amino acid attaches, TUC arm hairpin, DHU arm hairpin, anticodon arm hairpin has three nucleotides at the bottom (anticodon) and attach to mRNA codon
tRNA charging
20 different aminoacyl-tRNA synthetases, one for each amino acid, attaches an amino acid to tRNA by recognizing size, charge, and R groups of amino acids and nucleotide sequences on tRNA acceptor stem and anticodon loop.
