Transcription vs Translation

Central Dogma Transcription Translation

Chargaff’s Rule States that base ratio is 1:1 A=T CΞGCΞG Therefore if there are 300 Adenines there should also be 300 Thymines in DNA

Transcription Initiation – 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

Transcription Elongation 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

Transcription Termination 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 processing Before mRNA can leave the nucleus several things happen: 5’ cap is added, cap is guanine nucleotide with 2 extra phosphates Poly 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 splicing Appropriately joined Protein Introns Exons

Translation Initiation begins when the small ribosomal subunit attaches near the 5’ end of mRNA A 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 ribosome Elongation begins when the next tRNA binds Translation