A single triplet specifies only one aa v degenerate 1

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A single triplet specifies only one AA v. Degenerate 1. Most AA specifies by more than one triplet 2. Ex: Tyrosine = UAU or UAC a. Alanine = GCU or GCC or GCA or GCG i. If an AA has more than one codon specifying it, then usually the last base differs wobbles ( Figure 17.5) vi. One codon is a start codon AUG code for AA (Methionine (Met.)) 1. Marks the beginning of protein synthesis for the ribosome vii. Three stop codons 1. UAA, UAG, UGA 2. Do not code for AA 3. Function trigger termination of protein synthesis viii. Reading Frame 1. Ex: The red dog ate the bug a. Mutation delete the “t i. “her edd oga ehe bug” ix. Universal ( Figure 17.6) 1. Viruses
2. Prokaryotes and Eukaryotes ° Transcription (DNA RNA) a. Initiation i. DNA is template for RNA Synthesis 1. One strand of DNA is going to be transcribed = template strand a. Template strand will be read from 3’ to 5’ direction 2. Other Strand not translated ii. Promoter 1. Specific DNA Sequence on transcriber strand at beginning of a gene at the 3’ end a. Upstream End (3’) 2. Designates the starting site of transcription 3. However, not transcribed iii. RNA Polymerase 1. No primer needed 2. Binds to promoter a. Unwinds helix b. Begins process of transcription 3. RNA synthesized in the 5’ to 3’ direction 4. Complimentary to DNA a. Anti-parallel relationship b. Ex: i. 5’ (Upstream) A T G A C T 3’ (Downstream) 1. DNA (Non-Transcribed ii. 3’ (Promoter) T A C T G A 5’ 1. DNA Template iii. 5’ A U G A C U 3’ 1. RNA
b. Elongation i. DNA Template Strand Read in 3’ to 5’ ii. RNA Synthesis is going to be anti-parallel 5’ to 3’ direction iii. RNA polymerase elongates the mRNA is 5’ to 3’ direction 1. Always adding to 3’ end of growing mRNA 2. Nucleoside triphosphates are being added a. Two of the phosphates are going to be removed i. Provides the E to drive the elongation c. Termination i. There are specific DNA sequences that are going to signal the RNA polymerase to stop ii. New transcript falls off of DNA template or helped off by protons ( Figure 17.7) d. mRNA modification i. Happens in Eukaryotes post-transcriptional modification 1. Pre – mRNA a. Not yet in correct form to provide information for protein synthesis 2. Alteration of mRNA ends a. 5’ end receives a 5’ cap i. modified form of Guanine (G) b. 3’ end receives a poly-A tail i. 50-250 Adenine Nucleotides that are added to 3’ end c. Function ( Figure 17.10) i. Important in export of mRNA ii. Protect RNA for degradation by exonucleases iii. Help the ribosome attach 3. RNA Splicing a. Transcription of DNA i. Stand of pre-mRNA
1. Exons Expressed a. Coding regions b. Are transcribed and translated 2. Introns Intervening Sequences a. Are transcribed but are not translated (non- coding) b. Must be removed before translation ii. Splicing 1. Process which removes introns from pre-mRNA 2. Happens in nucleus 3. Splicesome a. Proteins and small RNA’s b. Bind to introns c. Splice at boundaries between introns and exons d. Introns degrade e. Exons are put all back together, no more intervening sequence and right next to each other iii. Mature RNA ( Figure 17.11 & 17.12) 1. Smaller than pre-mRNA 2.

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