Table of Contents
What type of mutation was detected in a mutant of T4 phage?
In this article we will report on suppressor-sensitive mutants isolated in bacteriophage T4D. These mutations, designated amber (am), are conditional lethals in the sense that they form plaques on Escherichia coli strain CR63, but not on strain B. Wild-type bacteriophage form plaques on both strains.
What does T4 lysozyme do?
T4 lysozyme helps to release mature phage particles from the cell wall by breaking down the peptidoglycan. The enzyme hydrolyses the 1,4-beta linkages between N-acetyl-D-glucosamine and N-acetylmuramic acid in peptidoglycan heteropolymers of prokaryotic cell walls.
Which is the permissive host for a mutant of T4 phage?
Escherichia coli
The growth properties of twelve different amber (am) mutants of bacteriophage T4 gene 43 (DNA polymerase) were examined by using nonpermissive (su−) as well as permissive (su+) Escherichia coli hosts.
How many classes of R type mutants are found in T4 phage?
As we saw above, rapid lysis (r) mutants were found that mapped to three different regions of the T4 genome: rI, rII, and rIII.
How did Benzema identify deletion mutants of t4 phage?
Benzer’s work Some he classified as deletions, others as point mutations. By various crosses of the many different strains exhibited deletions and point mutations, Benzer located each point mutation into a sub-region of one of the cistrons, and ordered the point mutations within that sub-region.
What is amber mutation?
Amber mutations are the result of a base substitution that converts a codon specifying an amino acid into UAG, which signals chain termination. In certain strains of E. coli amber mutations are suppressed.
What is the role of lysozyme in DNA extraction?
Lysozyme is an enzyme used to break down bacterial cell walls to improve protein or nucleic acid extraction efficiency.
What is an amber suppressor mutation?
The CR63 bacterial strain turns out to have a serendipitously pre-existing amber suppressor tDNA mutation. tRNA molecules produced by the E. coli are able to “read through” the amber mutant in the phage DNA, thus producing a functional protein and “suppressing” the effect of the phage mutant.
Is T4 phage lytic or lysogenic?
T4 is capable of undergoing only a lytic lifecycle and not the lysogenic lifecycle. The T4 Phage initiates an E. coli infection by recognizing cell surface receptors of the host with its long tail fibers (LTF). A recognition signal is sent through the LTFs to the baseplate.
How does bacteriophage T4 protect its DNA from the host cells restriction enzymes?
Phage T4 protects its DNA from the two gene encoded gmrS/gmrD (glucose modified hydroxymethylcytosine (gHMC) restriction endonuclease) (CT), of pathogenic E. coli CT596, by injecting several hundred copies of the 76 amino acid residue nuclease inhibitor, IPI*, into the infected host.
Which of the following is conditional lethal mutant of bacteriophage?
Abstract. Sixteen conditional lethal mutants of bacteriophage T4D have been isolated which grow on Escherichia coli CR63 (a su+ streptomycin-sensitive K12 strain) but are restricted by CR/s (a streptomycin-resistant derivative of CR63). These mutants have been given the prefix str.
What was the significance of Deletion mapping?
Deletion mapping is a specialized genetic mapping technique that enables scientsts to determine the location of a specific gene on a chromosome. This technique is useful when the location of alleles, variants of a recessive gene, are known to be located within a specific region, but their specific location is unknown.
What is an ochre mutation?
An ochre mutation is a nonsense mutation that changes a sense codon (one specifying an amino acid) into the stop codon UAA, causing premature termination of the polypeptide chain during translation. The mutation, the codon, and the mutant are all called ochre.
What is the function of lysozyme enzyme released by bacteriophages?
T4 lysozyme helps to release mature phage particles from the cell wall by breaking down the peptidoglycan. The enzyme hydrolyses the 1,4-β linkages between N-acetyl-D-glucosamine and N-acetylmuramic acid in peptidoglycan heteropolymers of prokaryotic cell walls.
Which step lysozyme is released by bacteriophage?
penetration phase
Therefore the break down of the cell by the enzyme lysozyme forms a hole on the host cell and the bacteriophage inserts the DNA into the bacterial cytoplasm. So the correct answer is ‘penetration phase’.
How do intergenic and intragenic suppressor mutations differ?
Suppressor Mutations. A suppressor mutation reverses or partially reverses the effects of a different mutation. An intragenic suppressor reverses the effect of a mutation at a different site in the same gene. An intergenic suppressor reverses the effect of a mutation at a different gene locus.
How many amber mutations have we introduced into T4 lysozyme?
We have introduced amber mutations into all but the first codon of the T4 lysozyme gene. The resulting set of 163 mutant phages has been plated on a set of 13 amber suppressor strains, each of which inserts a different amino acid.
What are the temperature-sensitive mutations of bacteriophage T4 lysozyme?
Temperature-sensitive mutations of bacteriophage T4 lysozyme occur at sites with low mobility and low solvent accessibility in the folded protein Biochem. Biophys. Res. Commun, 153 ( 1988), pp. 862 – 868 pH-induced denaturation of proteins: a single salt bridge contributes 3–5 kcal/mol to the free energy of folding of T4 lysozyme
Are single amino acid substitutions in T4 lysozyme sufficient to inhibit plaque formation?
Of the resulting 2015 single amino acid substitutions in T4 lysozyme, 328 were found to be sufficiently deleterious to inhibit plaque formation. More than half (55%) of the positions in the protein tolerated all substitutions examined. Among (N-terminal) amber fragments, only those of 161 or more residues are active.
What are the effects of deleterious substitutions in T4 lysozyme?
The effects of many of the deleterious substitutions are interpretable in light of the known structure of T4 lysozyme. Residues in the molecule that are refractory to replacements generally have solvent-inaccessible side-chains; the catalytic Glu11 and Asp20 residues are notable exceptions.