photo.jpg

## TRANSFER OF GENETIC INFORMATION: THE CENTRAL DOGMA ### The Central Dogma * **Information stored in the nucleotide sequences of genes is translated into the amino acid sequences of proteins through unstable intermediaries called messenger RNAs** * **The mRNA codons on the mRNA are translated in...

## TRANSFER OF GENETIC INFORMATION: THE CENTRAL DOGMA ### The Central Dogma * **Information stored in the nucleotide sequences of genes is translated into the amino acid sequences of proteins through unstable intermediaries called messenger RNAs** * **The mRNA codons on the mRNA are translated into an amino acid sequence by the ribosomes** ### Transcription and Translation in Eukaryotes * **The primary transcript is pre-mRNA** * **A precursor to the mRNA** * **The pre-mRNA is modified at both ends, and introns are removed to produce the mRNA** * **After processing, the mRNA is exported to the cytoplasm for translation by ribosomes** ### General Features of RNA Synthesis * Similar to DNA synthesis except: * The precursors are ribonucleoside triphosphates * Only 1 strand of DNA is used as a template * RNA chains can be initiated de novo (no primer required) * The RNA molecule will be complementary to the DNA template (antisense) strand and identical to the DNA non-template (sense) strand * RNA synthesis is catalysed by RNA polymerases and proceeds in the 5'→3' direction ### Transcription vs. DNA Replication * RNA does not remain H-bonded to the DNA post-synthesis * RNA molecules are selective copies of much shorter segments of the DNA * **Both employ polymerases** * to make phosphodiester linkages * DNA ahead of synthesis is unwound * Building blocks are very similar to each other * RNA polymerase does not need a primer ### The “Transcription Bubble” * (5') CGCTATAGCGTTT (3') DNA nontemplate (coding) strand * (3') GCGATATCGCAAA (5') DNA template strand * (5') CGCUAUAGCGUUU (3') RNA transcript