Week 3: Transcription & Translation

bases

• CG - 3 H+ bonds & AT(U) - 2 H+ bonds

• pyrimidine: C & T (one ring), purine: A & G (two rings)

• stacking interaction

backbone

• nucleotide (sugar-phosphate) attaches bases

• polar H+ bonds

• major & minor to keep nonpolar groups from water

DNA vs RNA

• U not T

• double stranded helix vs single

• at 2` deoxy has H & ribose has OH-

transcription stages

• initiation - RNA pol binds to promoter to start at +1 site, ribonucleotides enter active site through template strand

• elongation - nucleotides grow from 3` to continue RNA chain

• termination - RNA folds back and is separated when encounter termination signal

transcription purpose

• uses DNA to make RNA strands for gene expression or protein

transcription strands

• template: complementary to bases on RNA, synthesized by RNA pol - RNA strand is made here

• coding: matches RNA transcribed 

• *made 5`-3`

translation stages

• initiation - start codon w/ ribosome subunits & aminoaxcyl tRNA

• elongation - amino acid sequence grows polypeptide chain w/ peptide bonds

• termination - reaches stop codon, ribosome subunits dissociate

codon vs anti

• 3 mRNA to specify amino acid

• 3 tRNA to base pair with mRNA

translation components

• ribosomes: large & small subunits

• mRNA & tRNA: instruction template & binds

• aminoaxcyl tRNA: charged w amino acid

• stage factors & energy sources (ATP to supply PE)

primary vs mature mRNA

• primary - introns & exons (non-coding strands)

• mature - only exons (introns removed from splicing)

directionality

• 5`cap - recognition & 3` poly(A)tail - prevent degradation

• RNA synthesized 5`-3`

• nucleotides add to 3`, read from 5`

bacterial vs eukaryotic

bacterial

• 1 RNA pol guided to promoter

• -35 box & -10 box directly to mature mRNA

• transcription & translation occur simeltaneously

eukaryotic

• 3 RNA pol recruited to promoter

• TATA box, splicing

• transcription in nucleus & translation in cytoplasm