An important validation of the genetic code occurred when George Streisinger determined the amino acid sequence of bacteriophage T4 lysozyme and of mu- tants induced by proflavin, a dye with a planar structure that can intercalate (fit) between successive base pairs in DNA and induce frameshift mutations- that is, mutations involving additions or deletions of a single base. Streisinger and colleagues found that a particular single-base insertion mutation could be suppressed, with wild-type function restored, by a mutation that evidently involved a single-base deletion at a nearby site. Shown below are portions of the amino acid sequence of wild-type T4 lysozyme and the putative double mutant. The remaining parts of the sequence were unchanged. Identify MRNA sequences that could encode each of these amino acid sequences and deter- mine whether your codon assignments are consistent with the genetic code. Wild-type ... Lys-Ser-Pro-Ser-Leu-Asn-Ala. .. Double mutant - .. Lys-Val-His-His-Leu-Met-Ala- ..

An important validation of the genetic code occurred when George Streisinger determined the amino acid sequence of bacteriophage T4 lysozyme and of mu- tants induced by proflavin, a dye with a planar structure that can intercalate (fit) between successive base pairs in DNA and induce frameshift mutations- that is, mutations involving additions or deletions of a single base. Streisinger and colleagues found that a particular single-base insertion mutation could be suppressed, with wild-type function restored, by a mutation that evidently involved a single-base deletion at a nearby site. Shown below are portions of the amino acid sequence of wild-type T4 lysozyme and the putative double mutant. The remaining parts of the sequence were unchanged. Identify MRNA sequences that could encode each of these amino acid sequences and deter- mine whether your codon assignments are consistent with the genetic code. Wild-type ... Lys-Ser-Pro-Ser-Leu-Asn-Ala. .. Double mutant - .. Lys-Val-His-His-Leu-Met-Ala- ..

Biology: The Dynamic Science (MindTap Course List)

4th Edition

ISBN:9781305389892

Author:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Publisher:Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter19: Genomes And Proteomes

Section: Chapter Questions

Problem 1ITD: Below is a sequence of 540 bases from a genome. What information would you use to find the...

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Knowing that the genetic code is almost universal, a scientist uses molecular biological methods to insert the human - globin gene (shown in the figure below (Links to an external site.)) into bacterial cells, hoping the cells will express it and synthesize functional - globin protein. Instead, the protein produced is nonfunctional and is found to contain many fewer amino acids than does -globin made by a eukaryotic cell. Explain why and give thoughts as to how to overcome this.
Knowing that the genetic code is almost universal, a scientist uses molecular biological methods to insert the human β-globin gene (Shown in Figure 17.11) into bacterial cells, hoping the cells will express it and synthesize functional β-globin protein. Instead, the protein produced is nonfunctional and is found to contain many fewer amino acids than does β-globin made by a eukaryotic cell. Explain why.
Based on this alignment, you can identify areas of the protein sequences that are key regions of the proteins. If you were to design a targeted mutagenesis programme to try to disrupt the activity of the proteins in this current alignment as part of a research programme, which THREE amino acid sequence regions (motifs) would you target? List your sequence motifs in order of preference (number 1 being your most confident target). Explain your reasoning for each motif
Shown below is an R loop prepared for electron microscopy by annealing a purified eukaryotic messenger RNA with DNA from a genomic clone containing the full-length gene corresponding to the mRNA. (a) How many exons does the gene contain? How many introns? (b) Where in this structure would you expect to find a 5′,5′-internucleotide bond? Where would you expect to find a polyadenylic acid sequence?
Below is a sequence of 540 bases from a genome. What information would you use to find the beginnings and ends of open reading frames? How many open reading frames can you find in this sequence? Which open reading frame is likely to represent a protein- coding sequence, and why? Which are probably not functioning protein-coding sequences, and why? Note: for simplicitys sake, analyze only this one strand of the DNA double helix, reading from left to right, so you will only be analyzing three of the six reading frames shown in Figure 19.4.
Consequences of the Wobble Hypothesis Point out why Cricks wobble hypothesis would allow fewer than 61 anticodons to be used to translate the 61 sense codons. How might wobble tend to accelerate the rate of translation?
As part of a project investigating potential new drug targets in the fight against malaria, you are seeking to clone the gene for a protein from the malaria parasite Plasmodium falciparum. You wish to express this protein in BL21 (DE3) cells, a standard laboratory strain of Escherichia coli. After purification of your protein, you run an SDS-PAGE gel and notice that the major band has lower molecular weight than expected, so you fear you are getting a truncated version. 1. What technique could you use to confirm that you are obtaining a shortened version of your intended protein? explain
As part of a project investigating potential new drug targets in the fight against malaria, you are seeking to clone the gene for a protein from the malaria parasite Plasmodium falciparum. You wish to express this protein in BL21 (DE3) cells, a standard laboratory strain of Escherichia coli. After purification of your protein, you run an SDS-PAGE gel and notice that the major band has lower molecular weight than expected, so you fear you are getting a truncated version. (a) Give TWO possible causes of your protein becoming truncated. explain
Although techniques are available for determining the sequences of amino acids in proteins, it is becoming more and more common to sequence proteins indirectly by determining the base sequence of the gene for the protein and then inferring the amino acid sequence from the genetic-code relationships. Suggest why the latter technique is being used for proteins.
In studies of frameshift mutations, Crick, Barnett, Brenner, andWatts–Tobin found that either three nucleotide insertions ordeletions restored the correct reading frame. Question: If the code were a sextuplet (consisting of six nucleotides),would the reading frame be restored by the addition or lossof three, six, or nine nucleotides?
• Explain the central dogma of molecular biology• How does the genetic code direct the structure of proteins that are synthesized in cells?
The genetic code is thought to have evolved to maximize genetic stability by minimizing the effect on protein function of most substitution mutations (single-base changes). We will use the six arginine codons to test this idea. Consider all of the substitutions that could affect all of the six arginine codons.(a) How many total mutations are possible?(b) How many of these mutations are “silent,” in the sense that the mutantcodon is changed to another Arg codon?(c) How many of these mutations are conservative, in the sense that an Argcodon is changed to a functionally similar Lys codon?