The Process Whereby A Gene Makes Its Protein Flashcards
transcription
gene (DNA) makes pre-mRNA
post transcriptional RNA processing
introns excised out of pre-mRNA; 5’ end capped w methyl-guanine; 3’ end gets poly-A tail
translation
ribosome reads mRNA, string amino acids together
post-translational processing
folding, adornment w chemical side groups, localization, possibly enzymatic cleavage, possibly joining w other proteins to form multimers
transcription factors
bind gene’s promoter to initiate transcription
acetyl groups
have neg charge that neutralizes positive lysines that grip neg charged DNA tightly so that DNA is loosen and transcription factors can bind
histone deacetylase
removes acetyl groups from histone = chromatin recondenses and transcription stops
elongation
RNA polymerase makes pre-mRNA
pre mRNA
same as coding strand but has uracils instead of thymines
coding strand
sense strand
noncoding template strand
antisense strand
RNA polymerase
transcribes the gene to make mRNA
termination of transcirption
specific sequences signals signal the end
rho protein
used by some bacterial and viral genes to terminate transcription; binds to RNA and moves toward RNA polymerase/DNA template complex; RNA polymerase slows down when it encounters specific termination sequence in gene’s DNA; rho protein catches up to RNA polymerase/DNA complex and knocks off RNA polymerase allowing RNA to separate from DNA template strand
intrinsic termination
rho-independent method; sequence ends w short segment of inverted GC-rich repeats followed by string of adenines (A); CG rich repeat gets transcribed then RNA forms hairpin due to complementarity to inverted repeats which causes RNA to fall of template
RNA polymerase II
in eukaryotes transcribes protein-coding genes and many noncoding RNAs including small nuclear RNAs (snRNAs), small nucleolar RNAs (snoRNAs)and microRNA (miRNA) precursors
polyadenylated
when pre-mRNA is cleaved; marked by highly conserved consensus sequence (AAUAAA)
5’ cap
5’ end is capped w methylated guanine that has extra phosphate group on its 5’ carbon using 5’ to 5’ linkage
poly-a-tail
after transcription approx. 250 adenosine monophosphates are added to 3’ end of mRNA by polynucleotide adenylyltransferase
RNA splicing
introns are excised out and exons spliced together
spliceosome
complex of proteins and RNAs excises the introns out of the pre-mRNA and splices exons together
small nuclear RNAs
combine w proteins to make small nuclear ribonucleoproteins (aka SNRPs)
self-splicing introns
fold into loops and lariats on their own
post transcriptional RNA processing
5’ cap + poly a tail put on then then introns are excised out and exons are spliced together in archaea and eukaryotes
splice site mutations
cause multiple RNAs to be produced
alternative splicing
allows one gene to make several different isoforms of its protein; allows one gene to make different proteins in different tissues
mature mRNA
has untranslated regions at 5’ and 3’ ends
RNA editing after transcirption
cleaved/edited by guide RNAs; nucleotides can be added/deleted/substituted; resultant mRNA might no match predicted sequence from gene’s coding sequence
ribosome
reads mRNA 3 bases at a time (called a codon) to ad one amino acid to growing polypeptide
STOP codon
terminates translation and releases polypeptide which is folded, adorned w chemical side groups + sent to where it needs to be = some join w other to form multimers; some get cleaved into multiple independently active peptides; some made inactive form and activated by cleavage
initiation of translation
proteins that bind to 5’ cap and poly-A-tail help ribosome bind mRNA
elongation factors
help ribosome chain amino acids together
tRNA
carries amino acids in for translation; mRNA codon tells which anticodon tRNA must have; specific tRNA for each amino acid
tRNA charging
ATP provides energy to tRNA to bring in amino acids
Shine-Dalgarno sequence
in bacterial mRNA orients ribosome
AUG codon
translation begins here
Kozak sequence
consensus sequence around START codon
initiation factors
help ribosome assemble; in eukaryotes 5’ cap and poly-a-tail both bind to initiation factors
missense mutation
one amino acid gets replaced by another: no effect to no protein activity; translation continues after mutation as downstream sequences get translated
nonsense mutation
creates STOP codon at site of the mutation; protein is truncated = abolishes protein’s activity; translation stops at that point downstream sequences do not get translated
ribosome reading frame
begins at START codon ends at STOP codon; deletion/insertion w multiple of 3 nucleotide does not shift reading frame (not multiple of 3 will shift reading frame and protein cannot function/new function)
ribosome reading
assembled polypeptide at P site next amino acid carried to A site = bond between new AA amino group and previous AA carboxyl group
STOP codons
UGA, UAA, and UAG
releasing factors
terminate translation
proteins left on mRNA
signals enzymes to degrade the mRNA
tmRNA
part tRNA part mRNA used by bacteria to rescue translation where there is no STOP codon; carries alanine and binds to A site to deliver it; adds 10 more AAs then uses its STOP codon to release the stalled ribosome
nonstop mRNA decay in eukaryotes
no STOP codon: ribosomes A site is hanging off which signals protein to attach to mRNA and degrade it from its 3’ end forward
post translation processing
folding, adornment, placement, and cleavage; ribosome makes polypeptide which must be processed into protein
