Transcription and Translation Flashcards
Transcription Def.
Copying DNA to make mRNA
Translation Def.
Converts mRNA into protein
RNA Outline
Long unbranched sigle strand chain of ribonucleotides joined by 3’ to 5’ phosphodiester bonds. 3 Types: messenger, ribosomal, transfer
Transcription Outline
Catalyzed by RNA polymerase (no primer) Transcribes a DNA strand reading 3’ to 5’ and creating RNA 5’ to 3’. Gene contains distinct promoter (start) and terminator (end) sequences
Untranslated Regions (UTR)
Part of mRNA that doesn’t code for protein but provides information for translation process
Coding Strand (sense) (Def.)
DNA strand that mRNA is identical to (barring Uracil)
Template (antisense) Strand (def.)
DNA strand that RNA polymerase uses to form mRNA
Gene Orientations on DNA strands
Are opposite to each other
Translation Bubble Outline
How RNA Polymerase moves along DNA
Polydenation Signal
Sequences of bases that act as terminator sequence for transcription
Components of Complex (Eukaryotic) Transcription
Activators, repressors, basal transcription factors, Coactivatord
Activators Def.
Proteins that bind to enhancer genes. Speeding up transcription rate
Repressor Def.
Proteins bind to silencer genes . Slow transcription
Coactivators Def.
Adapter molecules. Integrate signals from activators and repressors
Basal Transcription Factors Def.
When stimulated by activators they begin transcription by placing RNA at start sequence
Why Eukaryotic Transcription is more complex
More genes, more non-coding DNA and differentiated/ selective expression
Heterogenous Nuclear RNA (hnRNA)
RNA molecules synthesised RNA polymerase 2 calles primary transcripts
Post-Transcriptional mRNA Processing Modification
hnRNA modified 5’ Capping, splicing and 3’ poly(A) tailing
mRNA precursors 5’ Capping Outline
7-methyl-guanosine residue addition, 5’-5’ triphosphate link to 5’ mRNA, guanyltransferase (capping enzyme) catalyses. Cap binds sets of proteins
5’ Capping Functions
Protect 5’ end from nuclease, guides mRNA through nuclear pore and permits translation initiation
3’ poly(A) tailing mRNA precursors
After polyadenylation signal, endonuclease recruitment and mRNA cleaved poly(A) polymerase adds 40-250 A residues to cleaved (3’) end. Tail shortens after entering cytosol.
Poly(A) Polymerase Functions
Stabilises mRNA molecules, slows 3’ -exonucleases (enzymes cleave nucleotides) and facilitates mRNA nucleus exit
mRNA precursor splicing outline
Necessary for eukaryotes because of genes in different regions in mature mRNA. Non-coding sequences (introns) are cut out. Small nuclear ribonucleoproteins (snRNPs) form spliceossome which atacks 5’ intron end. 5’ becomes attached to A nucleotide forming DNA loop. Free 3’ end attacks 5’ end of other. 3’ and 5’ ends bond covalently
Relationship between protein mRNA codes for and splicing
mRNA that code for different proteins have different genes kept/cut
