1. Transcription Vocabulary of transcription: transcription - synthesis of RNA under the direction of DNA messenger RNA (mRNA) - carries genetic message from DNA to the ribosome for the synthesis of protein translation - synthesis of protein under the direction of mRNA ribosome - site of protein synthesis (translation) primary transcript - RNA that comes directly from the transcription of DNA codon - a triplet code of DNA (64 possible) that codes for an amino acid reading frame - indicates the proper starting & ending points for the transcription of DNA amino acid (AA) - building block of proteins based on a 3-letter code of DNA

2. Genetic Code 64 codons for 20 amino acids – Called a redundant code as different codons create the same amino acid AUG start … Methionine UAA, UAG, & UGA Stop – Each amino acid abbreviated by the 1 st 3 letters of the name

3. Transcription – Step 1 RNA polymerase II pries apart DNA – reads the DNA in the 3'-5' direction (sense strand) beginning at the start codon AUG binds to the DNA prior to the start codon in the promoter region – TATA Box 5'-TATAAAA-3" (full sequence about a dozen nucleotides long) – used for the attachment of transcription factors that aid in the binding of RNA pol II » transcription factors + RNA pol II is called the transcription unit – assembles RNA in the 5'-3' direction can be assembled by multiple RNA pol II enzymes – transcription continues until a stop codon (terminator) is reached stop codons are UAA, UAG, UGA the pre-mRNA also continues a poly-A tail (AAUAAA) before it is cut free from the growing strand RNA pol II falls off of the DNA

4. Transcription – Step 2 pre-mRNA is now modified – 5' receives a cap that consists of GTP and around 20-40 nucleotides – 3' end receives a cap of A (50-250 nucleotides) to extend the poly-A tail both help protect the mRNA from degradation are considered NTR - nontranslated regions – splicing occurs as the introns (non-coding regions) are excised leaving only the exons (coding regions cut by snRNPs (small nuclear RNA) - specialized RNA that remove the introns spliceosome releases the introns and joins the exon regions introns may also be removed via self splicing in some organisms alternate splicing may give rise to different proteins from the same transcriptional unit The finished length of RNA is now called the mRNA unit