Lecture 19 Flashcards
transcription and translation
rna synth and protein synth
Transciption = making copy of the gene, taking the DNA in the langugae od nucleotides to RNA
translate = from nucelotides to aa to make proteins for whatever cell wants to do.
diff bn DNA and RNA
sugar differences = ribose vs deoxyribose
base differences the complementary base in DNA = T, in RNA = U
DNA = double stranded
RNA = single stranded
DNA = helix
RNA = will fly on themselves to diff shapes, structures and fns
transcription vs DNA rep
sim vs diff
similiaritis
Both in nucleus
Both use DNA template
Direction of synth = 5’ to 3’.
Differences
When dna rep happens = both strands as template fro DNA rep
In transcription = one or the other. Only one strand is the template,
Enzymes = DNA poly needs helicase to open the 2 strands, RNA poly doesn’t need helicase activity, moves on DNA molecule, opens ahead and closes behind. It can break the H bond itself
Substrate, DNA poly uses deoxyribo nucelotides, RNA poly uses ribo nucleotides
initiating and terminating sequences
promotors = bind to RNA poly and allow transcription initiation
terminators = det end of trasncription
transcription initiation
promotors = region of the DNA that…
- det initiation site
- identify template strand.
consensus sequences
promotors contain this
short sequences universally recognized by transcription factors nad RNA poly
ex. TATA box and -10/-35 regions
transcription initiation in pro vs euk
pro = RNA poly directly reco the promotor sequence
euk = RNA poly II needs transcription factors to redo the promoter,
= proteins that bind DNA so can bind RNA poly to DNA,
1st factor binds to promotor and makes DNA bend, more factors come and find = huge complex on motor so that RNA can reco the complex,
rna is phos to activate and starts transcribing.t
transcription termination in pro.
DNA has a GC rich region, 2 sequences repeated and inverted followed by a string of A
will transcribe sequence, then mRNA will fold on itself bc of repeated sequence + slow the poly.
+ weak AU bonds = ready to detach = transcription terminates (RNA falls off)
transcription termination in euk
RNA poly II transcribes past the end of a gene,
transcribes a polyadenylation signal (AAUAAA) in the RNA,
a protein reco this and cleaves the RNA after this signal but before a GU rich sequence
eukaryotic pre-mRNA processing, splicing
in euk, have coding and non coding regions,
when rna copy is made, non coding region is removed.
non coding = introns
coding = exons
removing introns = splicing
exons joined together
alternative splicing = alternative proteins
eukaryotic pre-mRNA processing, capping
adding a G nucleotide to the 5’ end of the pre mRNA
added unusually, the 5’ of both C bonded covalently to e/o
weird binding = protects the mRNA, allows it to go to cytoplasm for translation.
+
allows it to be reco by ribs when being translated
eukaryotic pre-mRNA processing, polyadenylation
adding a string of A nucleotide to 3’ end of RNA
protects 3’ end
stabilize mRNA + lasts longer in cytoplasm
initiates translation. t
rotects the 3′ end from degradation.
Stabilizes the mRNA and helps it last longer in the cytoplasm.
Works with the 5′ cap to help initiate translation and regulate export.
transcription => translation in pro
occur simultaneously in same location in the cell
location of transcription dn translation in euk
occur sequentially,
transc= nucleus
transl= cytoplasm
language of nucleotides
every 3 ribonucleotides = a codon
each aa is specified by a codon
all codons make up the genetic code (64 codons = (61 sense + 3 nonsense))
features of the genetic code
made of triplets
comma less
nearly universal
1 intiation codon, 3 stop codons
non overlapping = each nucleotide is part of one codon
degenerate = multiple codons code for the same aa = redundancy in the codde
DOESNT MEAN EACH CODON CODES FOR MULTIPLE aa
ordered = codons for similar aa differ by one base
