Explore BrainMass

Explore BrainMass

    Ames test to determine if an external agent can act as a mutagen

    Not what you're looking for? Search our solutions OR ask your own Custom question.

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    The Ames test is used to determine if an external agent (such as a chemical) can act as a mutagen. In this test, several different his- strains of Salmonella typhimurium are used. Each strain contains a different class of mutation in the his gene. Each mutant is exposed to the chemical to determine if the chemical can revert the mutation back to wild type (his+), and at what frequency.

    (a) How can such prototrophic revertants be identified?

    (b) In this experiment, three different strains of Salmonella were used to determine the mutagenic properties of three different chemicals. The following table lists the type of mutation in each his mutant and the number of revertants obtained with the addition of each of the three chemicals. Are any of the chemicals putative mutagens? If so, what type of mutations do they cause? Justify your answer.

    Strain Type of his-mutation Water Chemical1 Chemical2 Chemical3
    Strain1 T to G base substitution 2 2000 3 5
    Strain 2 G to A base substitution 1 1 4 1700
    Strain 3 Single base deletion 3 2 4 3.

    © BrainMass Inc. brainmass.com December 16, 2022, 10:14 am ad1c9bdddf

    Solution Preview

    (a) A petriplate with agar lacking histidine is prepared and the histidine requiring mutant S.typhimurium strain is plated on the petriplate. A filter paper disk soaked in mutagen is placed in the centre of the petriplate. If mutation occurs, the strain regains its ability to synthesisze histidine and will be able to grow on the plate. All the colonies growing on the plate are revertant bacteria ...

    Solution Summary

    The solution assists with identifying prototrophic revertants.