AP Bio - Modern Genetics
Protein Synthesis • Start with primer • New strand is 5’ to 3’ • TATA Box - TTAATTAA • RNA Polymerase - Reads and matches bases (One recipe; only reads leading strand) • Single strand produced; mRNA • Now produced pre-mRNA (You need exon, not intron) • Introns create spaces, need ligase to connect exons to make true mRNA. • Adds a poly A tail (on 3’ side) and 5’ (prime) cap (on 5’ side) used for defense • Leaves through pore to ribosome. • Messenger RNA will attach to ribosome • Transfer RNA comes in (reads in sets of 3) (mRNA - Codon; tRNA - Anticodon = amino acid) • Peptide bonds connect the amino acids (GDP energy used) Creates primary structure H2O is released since it is dehydration • Turns into secondary by alpha beta • Turns into tertiary by H, hydrophobic • S-S, Covalent, ionic bonds • Turns into quaternary structure at Golgi Apparatus. Goes through protein synthesis twice before becoming quaternary structure; both proteins sent to Golgi apparatus to be glued together. Chapter 17 - From Gene to Protein I. History: Genes Specify Proteins ! A. Garrod - Inborn errors of metabolism ! ! 1. Said that genes dictate the production of a speciﬁc enzyme. ! B. Beadle and Tatum ! ! 1. One gene-one enzyme hypothesis ! ! 2. Says that each gene produces its effects by controlling the synthesis of ! ! a single enzyme. ! ! 3. AKA: One gene-one polypeptide - pg 311 II. Genetic Code ! A. Triplet Code - Set of three nucleotide long words that specify amino acids for ! polypeptide chains ! B. Codon - Each group of three bases specifying an amino acid. ! C. Nirenberg - Deciphered ﬁrst codon ! D. There is redundancy (multiple codons for one amino acid) but not ambiguity ! (one code speciﬁes for two amino acids) ! E. Polyribosome - Clusters of ribosomes on same mRNA. III. Protein Synthesis ! A. DNA directs protein synthesis through RNA ! B. mRNA carries blueprint for a particular protein out of the nucleus. ! ! 1. Transcription - Copying of the genetic message into a molecule of ! ! mRNA (occurs in nucleus)
AP Bio - Modern Genetics
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! 2. DNA is the template (3’ to 5’) ! 3. RNA Polymerase - Binds to promoters, separates strands of DNA and ! hook together RNA nucleotides (only add to 3’ end) ! ! a. TATA Box - Where RNA polymerase H binds (eukaryotes) ! ! b. Transcription Factors - Aid polymerase in locating promoters ! ! such as the TATA Box ! ! c. Reads in sets of 3 called codons. ! 4. Termination site on DNA indicates end in prokaryotes ! 5. Eukaryotes - Pre-mRNA separates from DNA at the polyadenylation ! signal, but RNA polymerase continues to transcribe until it falls off the ! DNA. C. Pre-mRNA processing in eukaryotes ! 1. Heterogenous nuclear RNA (hnRNA) contains introns and exons. ! ! a. Introns not used (stay IN nucleus) ! ! b. Exons used (EXIT nucleus) ! 2. Small nuclear ribonucleic proteins (snRNP’s/snurps) help excise introns ! and fuse exons. ! 3. Splicosomes - Snurps and proteins working together ! 4. Poly A tail is added to 3’ end which a 5’ cap is added to the 5’ end. ! ! a. Prevent damage to mRNA as it leaves nucleus ! ! b. Helps mRNA leave nucleus ! ! c. Helps mRNA attach to ribosome. D. rRNA - Formed in nucleoli, makes up part of ribosome. ! 1. Ribosomes - Binding site for rRNA. E. Translation ! 1. Initiation - Brings mRNA and tRNA together by means of factors (start ! codon is AUG) ! 2. Elongation - Amino acids are added with aide of elongation factors. ! ! a. Codon Recognition - mRNA codon on A site forms H bonds with ! ! anticodon of incoming tRNA. ! ! b. Aminoacyl tRNA synthetase matches amino acid with correct ! ! tRNA ! ! c. Peptidyl transferase catalyzes the formation of a peptide bond ! ! between polypeptide at P site and amino acids at A site. ! ! d. Wobble Effect - Exact base pairing is not always necessary. ! 3. Translocation ! ! a. A site on ribosome holds tRNA carrying the next amino...
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