15. Both sides of the DNA can be utilized at the same time, but synthesis occurs in the 5’ 3’ direction
16. More about the regulatory region later…for now, know that a promoter “promotes” transcription!
17. We say that the regulatory region is “upstream” from the coding region of the gene. The promoter bases are NOT transcribed.
18. Once transcription begins, many RNA polymerases may read the DNA at once to get hundreds of mRNA templates made simultaneously—very efficient!
19. What stops transcription? A sequence of bases on the DNA that cause the RNA polymerase and mRNA strand to be released—remember mRNA has to be modified before it can leave the nucleus!
20. This is an electron micrograph of many RNA polymerases acting at once. DNA Many mRNAs being formed
36. Here’s the whole picture: just memorize AUG as the start codon and remember all polypeptide chains begin with methionine. No need to memorize more.
42. The amino acid is attached to the 3’ end of the convoluted strand.
43. AUG on the mRNA is matched with UAC on the tRNA and methionine is now in place.
44. The next codon is “read” and the next aa is placed. The peptide bond is formed between the amine group of one aa and the carboxylic acid group of the next aa.
46. Once the peptide bond forms, tRNA releases its aa and is recycled. The ribosome shifts down the mRNA strand in a, you guessed it, 5’ 3’ direction.
47. Now we simple repeat until a stop codon is reached….elongation continues.