Transcription vs Translation

Central Dogma

TranscriptionTranslation

Chargaff’s RuleStates that base ratio is 1:1A=TCΞGTherefore if there are 300 Adenines there should also be 300 Thymines in DNA

TranscriptionInitiation – RNA polymerase attaches to the promoter region on the DNA and begins to unzip the DNA. Promoter normally contains TATA box, sequence of T-A-T-A

TranscriptionElongation occurs as RNA polymerase unzips the DNA and assembles RNA nucleotides using one strand of the DNA as a template. This occurs in the 5’ 3’ direction

TranscriptionTermination occurs when the RNA polymerase reaches a special sequence of nucleotides that servers as a termination point. In eukaryotes the termination region is often AAAAAAAAAAA.

mRNA processingBefore mRNA can leave the nucleus several things happen:

5’ cap is added, cap is guanine nucleotide with 2 extra phosphatesPoly A tail added to 3’ end. Tail has about 200 adenine nucleotides.RNA splicing – introns are removed, exons are spliced together. Small nuclear ribonucleoproteins or snRNP’s delete the introns Alternative splicing

RNA splicingAppropriately joined

Protein

IntronsExons

TranslationInitiation begins when the small ribosomal subunit attaches near the 5’ end of mRNAA tRNA carrying an amino acid attaches to the mRNA at the start codon AUG. The large ribosomal subunit attaches to the mRNA forming a complete ribosomeElongation begins when the next tRNA binds

Translation