BIOL 1st Edition Lecture 19 Outline of Last Lecture I Chromosomes II Sex Linked Inheritance III Genetic Problems with X Linked Genes IV V VI How to Solve a Genetics Problem Chromosomal Alterations Chromosomal Alterations Based on the Number of Chromosomes VII Chromosomal Alterations Based on Chromosomal Structure Changes VIII HW Genetics Problems with Solutions due 4 15 14 Outline of Current Lecture I DNA and Cell Activities II Transcription III Translation Current Lecture Chapter 17 Molecular Genetics I II DNA and Cell Activities a Inherited DNA controls the cell s activities b It has the code for how to make enzymes and other proteins c DNA does NOT make protein directly d How to make proteins i DNA is copied to an RNA molecule called messenger RNA mRNA ii mRNA programs the making of proteins e Central Dogma of Molecular Biology i The process of making proteins is called the central dogma of molecular biology ii DNA transcription mRNA translation protein iii Transcription synthesis od RNA from a DNA template iv Translation synthesis of protein using information in mRNA molecule Transcription synthesis of RNA from a DNA template a Information in DNA is copied into an RNA molecule b mRNA is made by an enzyme called RNA polymerase III c RNA polymerase binds to DNA at the beginning of a gene at a specific place called the promoter d RNA polymerase is guided to the promoter by special proteins called transcription factors e Once at the promoter RNA polymerase moves along the DNA and separates the two strands f One of the two strands acts as a template to make RNA by the base pairing rules g RNA nucleotides C G A U line up properly on the DNA template strand remember that RNA nucleotides include U in place of T by HYDROGEN BONDING h RNA polymerase links the lined up RNA nucleotides together to form the RNA molecule i RNA is made of approximately 60 nucleotides second j As RNA is made it peels off the DNA k Then 2 DNA strands come back together l Transcription stops at a place called the terminator m At the terminator RNA polymerase releases the finished mRNA molecule and then falls off the DNA i Base Pairing Rules for DNA 1 C G 2 A T ii Base Pairing Rules for DNA RNA pairing 1 DNA 3 G C A T 5 2 mRNA 5 C G U A 3 Translation synthesis of protein using mRNA information a mRNA polymer of 4 different nucleotides G C U A b Proteins polymers of 20 different amino acids c The Genetic Code how it translates the language of nucleotides to the language of amino acids i 1 nucleotide 1 amino acid 1 Could only code for 4 amino acids ii 2 nucleotides 1 amino acid 1 Number of combinations of 4 things taken 2 at a time 42 16 could only specify 16 different amino acids iii 3 nucleotides 1 amino acid 1 43 64 possible combinations of amino acids iv Each 3 nucleotide code word is called a codon codes for some particular amino acid v First codon was deciphered in 1961 by Nirenberg 1 He made a synthetic mRNA test tube poly u 2 Then translated it in vitro in test tube 3 The protein that was made was composed entirely of the amino acid phenylalanine 4 Therefore the codon UUU codes for the amino acid phenylalanine 5 Later 64 possible combinations of nucleotides were deciphered a 61 code for amino acids b 3 don t code for anything but are signals to stop translation called stop codons 6 All living things share the same genetic code 7 Indicates that the genetic code was established very early in evolution example of unity in life d Tools for the process of translation i mRNA RNA molecule that carries the coding information a series of codons that must be decoded one right after the other 1 Translation starts at the first start codon from the 5 end of the molecule 2 The region from the CAP a stabilizing and regulatory structure to the start codon is not translated into amino acids it is called the 5 untranslated region 5 UTR 3 Translation ends at a stop codon NOT at the very end of the mRNA 4 The region between the stop codon and the 3 end is NOT translated and is called the 3 untranslated region 3 UTR 5 The 3 end of the mRNA has a string of A s called the poly A tail which acts to stabilize mRNA and regulate translation ii tRNA functions as a decoder that pairs the right amino acid with its codon amino acids DO NOT recognize their own codons 1 tRNA is a small RNA 80 nucleotides that is shaped like a L but upside down and backwards 2 One end has a sequence of 3 nucleotides called the anti codon which recognizes a particular codon on the mRNA by the base pairing rules 3 The other end of the tRNA carries the correct amino acid the amino acid coded for by the codon that is recognized by the anti codon of the tRNA iii Ribosomes organelle that coordinates the pairing of tRNAs with their mRNA codons 1 Ribosomes are composed of 2 subunits large and small 2 The 2 ribosomal subunits are separate except when translating mRNA into protein 3 Each ribosome has one binding site for mRNA and 3 binding sites for tRNAs a E site b P site c A site e The process of translation i Synthesis of proteins using information in the mRNA ii Occurs in 3 stages 1 Initiation requires energy input from cell AND enzymes a mRNA and special tRNA indicator RNA binds to a small subunit of ribosome b Requires a set of initiation factors c Initiator tRNA anticodon is base paired with the start codon on mRNA d Large subunit of ribosome binds with initiator tRNA in the P site functioning ribosome 2 Elongation requires energy input from cell AND enzymes a A tRNA with correct anticodon for the next codon one after the start codon binds in the A site with its anticodon base pairing with next codon b A peptide bond forms between the 2 amino acids on the tRNAs in the P and A sites c The connected amino acids stay attached to tRNA in A site but are released from tRNA in P site d The ribosome moves over one codon so that the tRNA in the P site now without an amino acid is in the E site and is released e The tRNA that in the A site is now in the P site still holding the growing amino acid chain and the A site is over the next codon f Cycle is repeated until protein is complete the ribosome always moves one codon at a time from 5 to 3 3 Termination requires ONLY enzymes a Where translation stops b Ribosome comes to a termination codon it does not code for any amino acid so no tRNA pairs with it c A release factor binds in A site this …