Presentation on theme: "Topic 7 Cont’d Transcription and Translation. Transcription Basics DNA vs. RNA."— Presentation transcript:
Topic 7 Cont’d Transcription and Translation
Transcription Basics DNA vs. RNA
Transcription Basics cont’d Directionality: read 3’-5’; made 5’-3’ Promoter & TATA boxes Nucleoside triphosphates Contains the sense strand and antisense strand Sense strand = always 5’-3’ and is the same as the mRNA that is produced except T for U Antisense strand = always 3’-5’ and is the strand that forms the template and is transcribed.
Translation The process of polypeptide/protein production using mRNA as a guide Requires: mRNA transcript tRNA tRNA activating enzymes ribosomes genetic code…..
The Genetic COde
The Genetic Code cont’d It’s a triplet code (codon) = 3 bases code for 1 amino acid There are 64 different codons Duplication = degeneracy = possible for 2 or more codons to code for the same amino acid Code is essential universal (find me 2 exceptions by next class for 1 point e.c. each)
tRNA All tRNAs have base-paired ds sections that become loops Triplet bases complementary to mRNA codons…called anticodons A 3’-5’ CCA terminal end for amino acid attachment The above permit 3 distinct binding attachment of the tRNA to the ribosome
tRNA a S = F example The base sequence of tRNa molecules vary = some variable features in its structure An extra small loop is sometimes present The bp sections are sometimes helical Results in: A distinctive 3-d shape Distinctive chemical properties ALLOWS THE CORRECT AA TO BE ATTACHED TO THE 3’ END BY A tRNA ACTIVATING ENZYME (aminoacyl-tRNA sythetase) There are 20 different tRNA activating enzymes – one for each of the 20 diff. AA
Ribosome Basics Composed of protein and rRNA Consist of 2 subunits (small and large) Possess 3 binding sites for tRNA (2 tRNAs can bind at the same time) Possess a binding site for mRNA Free vs. Bound (RER) 80S in Euks vs. 70S in Proks & Euk. organelles
Ribosome (2 site version)
Translation Step 1 - Initiation
Polysomes & Movie Time on/movie.htmhttp://vcell.ndsu.nodak.edu/animations/translati on/movie.htm