BSC2010 BIOLOGICAL SCIENCE 1 SPRING 2012 STUDY GUIDE 17 TRANSLATION Vocabulary Addition mutations o Mutations that result in the addition of extra DNA are called insertions Insertions can also cause frameshift mutations Aminoacyl site A site o Tetracycline and streptomycin bind to the A site and inhibit tRNA o binding tRNA with anticodon complimentary to next codon in mRNA binds to A site Aminoacyl tRNA synthetases o There are 20 different aminoacyl tRNA synthetase enzymes one for each of the 20 different amino acids o Recognize unique sequence and structural features of the tRNAs and attach appropriate amino acid to the tRNA o Create what is called charged tRNA or activated amino acid o Energy for reaction is derived from the high energy phosphate bonds in ATP Anticodon Base pair substitutions o Different tRNAs have different 3 nucleotide anticodons that will recognize different codons in mRNA by complementary base pairing o A base pair substitution replaces one nucleotide and its partner with another pair of nucleotides When these occur in the protein coding region of a gene they are further classified according to their effect on the genetic code Charged tRNA o which its cognated amino acid is adhered Its role is to deliver the amino acid to the ribosome where it will be incorporated into the polypeptide chain that is being produced Codon Deletion mutations o The code defines how sequences of three nucleotides called codons specify which amino acid will be added next during protein synthesis o Insertion and deletion mutations are additions or losses of nucleotide pairs in DNA Exit site E site Places growing polypeptide chain in P site and uncharged tRNA in E site from which it exits ribosome Frameshift mutations a genetic mutation caused by indels insertions or deletions of a number of nucleotides that is not evenly divisible by three from a DNA sequence o o GTP o a purine nucleoside triphosphate It can act as a substrate for the synthesis of RNA during thetranscription process Its structure is similar to that of the guanine nucleobase the only difference being that nucleotides like GTP have aribose sugar and three phosphates with the nucleobase attached to the 1 and the triphosphate moiety attached to the 5 carbons of the ribose Missense mutations still code for an amino acid but the amino acid is different from that encoded in the original unmutated gene o Mutations are heritable changes in the base pair sequence of DNA Mutations mRNA o Has the sequence information from the gene that determines amino acid sequence of protein Nonsense mutations change an amino acid codon into a stop codon nearly always leading to a nonfunctional protein o Amino acid in P site cleaved from tRNA and attached to amino acid in A Peptidyl site P site site with new peptide bond Peptidyl transferase Peptide bond is catalyzed by peptidyl transferase an enzyme that is really a ribozyme made of rRNA Point mutations Point mutations are changes in just one base pair of the DNA The change of even a single nucleotide in a DNA template strand can lead to the production of an abnormal protein o The types of point mutations that are possible are substitutions deletions or additions Polyribosome o It takes 1 2 minute to synthesize an average sized protein 200 500 amino acids in this manner o The rate of protein production is increased significantly by having multiple ribosomes attach and translate a mRNA at the same time These complexes are called polyribosomes is a way of breaking a sequence of nucleotides in DNA or RNA into three letter codons which can be translated in amino acids is a protein that allows for the termination of translation by recognizing the termination codon or stop codon in a mRNA sequence Reading frame Release factors Ribosome o The workbenches where translation takes place and the source of the enzymatic activity peptidyl transferase for peptide bond formation o o o o o o o Large complexes made of proteins and rRNA ribosomal RNA o Consist of two subunits large and small o When not in the process of synthesizing proteins the subunits are not connected float free of each other in the cytoplasm o Assembled ribosomes have three sites for binding tRNA a peptidyl P site an aminoacyl A site and an exit E site These names reflect the state of the tRNAs found at each of these sites Ribozyme o o o o rRNA o Silent mutations Start codon Stop codon an RNA molecule with a well defined tertiary structure that enables it to catalyze a chemical reaction Ribozyme means ribonucleic acid enzyme It may also be called an RNA enzyme or catalytic RNA is the RNA component of the ribosome the enzyme that is the site of protein synthesis in all living cells have no effect on the amino acid produced by a codon because of the redundancy in the genetic code is generally defined as the point sequence at which a ribosome begins to translate a sequence of RNA into amino acids or termination codon is a nucleotide triplet within messenger RNA that signals a termination of translation Substitution mutations Translation o The process of making a linear chain of amino acids aka a polypeptide chain in which the amino acids are joined by peptide bonds The sequence of amino acids in the polypeptide chain is determined by the sequence of nucleotides in the mRNA Every three nucleotides in the mRNA is a codon that codes for one amino acid o chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologouschromosomes Translocation tRNA o The components that actually perform the translation from nucleotide to amino acid language Principles and Concepts Know how the interactions between aminoacyl tRNA synthetases and tRNAs and the complementary base pairing between the anticodon of tRNAs and the codons in mRNA contribute to the specificity of translation o Point of attachment of specific amino acid that will be incorporated into protein in response to the codon recognized by this tRNA s anticodon o Different tRNAs have different 3 nucleotide anticodons that will recognize different codons in mRNA by complementary base pairing o Aminoacyl tRNA synthetase There are 20 different aminoacyl tRNA synthetase enzymes one for each of the 20 different amino acids Recognize unique sequence and structural features of the tRNAs and attach appropriate amino acid to the tRNA Create what is called charged tRNA or activated amino acid Energy for reaction is derived from the high energy phosphate bonds in
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