To analyze:
Charles Yanofsky in
Introduction:
Base pair substitution is a type of mutation where one nucleotide base pair is replaced by another. There are many possible types of replacements in base pairs-
Transition type: One Purine nucleotide by another Purine.
One Pyrimidine nucleotide by another Pyrimidine.
Transversion type: One Purine is replaced by Pyrimidine or vice versa.
Again, there are two possible types of mutation by the replacement of nucleotide base pair:
Silent or Synonymous Mutation: In this case, the amino acid remains the same even after the replacement of the nucleotide base pair, therefore, function of the protein is not affected.
Missense Mutation: In this type of mutation, the replacement of nucleotide base pair causes a change in amino acid resulting in the loss of protein function.
Charles Yanofsky found many Missense mutations while characterizing tryptophan synthetase, the product of trp A gene.
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GENETIC ANALYSIS: INTEGRATED - ACCESS
- The authors state: "Properties of the single mutants K557R, D591V and K617A, a double mutant, D591V/K617A, and a triple mutant, K557R/D591V/K617A, were evaluated to find an allosteric binding site for citrate." The numbers between the letters represent the residue number altered. The letter in front was the wild type and the letter afterwards is the mutant. How would the the triple mutations K557R and D591V and K617A alter the overall protein? O lower the # of charges, increase the pl O increase the # of charges, increase the pl O lower the # of charges, lower the pl O lower the # of charges, increase the pl O no change in the # of charges, increase the pl O no change in the # of charges, lower the plarrow_forwardAre genes A, D, and E all under the control of operator O? Explain your reasoningarrow_forwardThe SARS-CoV-2 genome has a cap at its 5'-end that is the same as the one seen on most human mRNA molecules. The nsp12 RNA-dependent RNA polymerase acts like cellular RNA polymerase and initiates RNA synthesis by synthesizing a dinucleotide from two nucleoside triphosphates. What other enzymes are needed to add a cap to the nsp12 product? Describe the chemical nature of the products of each of these enzymesarrow_forward
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- You are interested in studying resistance to heavy metals and have selected the yeast Saccharomyces cerevisea to conduct your studies. You have recovered a deletion mutant that does not tolerate high concentrations of zinc (grows poorly in zinc containing media ) and have designated the mutant pgz-1 (for poor growth in zinc ). (a) What is the advantage to the type of mutant used in this work? What class of mutagen was likely use to generate pgz-1? ( b) Do you expect the PGZ gene to be expressed in your mutant? Explain.arrow_forwardA glycine residue is in position 210 of the tryptophan synthetase enzyme of wild-type E. coli. If the codon specifying glycine is GGA, how many single-base substitutions will result in an amino acid substitution at position 210? What are they? How many will result if the wild-type codon is GGU?arrow_forwardConsidering that prokaryote genomes do not have large introns, how is it possible to move a eukaryotic gene into a transformed bacterium, since they lack a spliceosome?arrow_forward
- A mutant has no activity for the enzyme isocitrate lyase.Does this result prove that the mutation is in the geneencoding isocitrate lyase?arrow_forwardA classic way to isolate thymidylate synthase-negative mutants of bacteria is to treat a growing culture with thymidine and trimetho- prim. Most of the cells are killed, and the survivors are greatly enriched in thymidylate synthase-negative mutants. (a) What phenotype would allow you to identify these mutants? (b) What is the biochemical rationale for the selection? (That is, why are the mutants not killed under these conditions?) (c) How would the procedure need to be modified to select mam- malian cell mutants defective in thymidylate synthase?arrow_forwardYou are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene. A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located? B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?arrow_forward
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