You have synthesized 3 new compounds and give them the names: Com1, Com2 and Com

Question

You have synthesized 3 new compounds and give them the names: Com1, Com2 and Com3. You conduct an Ames test and determine that all three compounds are mutagenic. You then test the capacity of mutations caused by your compounds to be reversed by other known mutagens You get the following results 5. Reversed by Mutations EMS Hydroxylamine Proflavin produced by Bromouracil No Yes Yes What conclusions can you make about the nature of the mutations produced by Comi Com2 Com3 Yes No Yes Yes No Yes No No Yes these compounds? i. Com ii. Com2 ii. Com3 You are studying the effects of mutations caused by the new compounds in question 5 You expose Drosophila larvae to either Com 1, Com2 or Com3, then collect the 6. mated them with unexposed

Explanation / Answer

Ames test is used to reveal the mutagenicity of compounds. In Ames test, the various strains of Salmonella which are having mutation in histidine synthesis are used. These strains are called auxotrophic as need Histidine in their medium for survival and can be denoted as His-. Culturing His- in media containing the mutagens leads to mutation in Histidine encoding genes to revert the mutation to His+,(iemutatgens revert the His- salmonella to His+ ). His + can synthesise Histidine by their own and can survive in Histidine less growth medium also.Thus Ames test is used to study the mutagenitic ability of various chemicals.

Here, there are three compounds and the mutation caused by theses compounds are reverted by some other chemicals namely,5- Bromouracil, EMS( Ethyl methonaesulphonate),hydroxylamine, Proflavin.

Comound 1:From the table we could understand that the mutation caused by Compound 1 is reverted by 5-Bromouracil and EMS.5-bromouracil is a base analog, it is a brominated uracil. It substitutes Thymine in DNA and it pairs with adenine.It causes a point mutation by base substitution.EMS produce random mutations in nucleotides by point mutations.The EMS add a alkyl group to the guanine in the DNA and during replication DNA polymerase place thymine and thymine pairs with this modified guanine. Thus it causes a point mutation. The mutation caused by the Compound 1 is overcame by 5-Bromouracil and EMS by point mutation, that means compound 1 causes a point mutation.

Compound 2: The muatation caused by the compound 2 can be reverted by Proflavin only. Proflavin is an intercalating agent which intercalates into the DNA strand. It can induce deletion or insertion mutation.If prflavin intercalately into a template DNA strand, in the newly synthesising strand a randomly chosen nucleotide is added, resulting insertion mutation. If proflavin, interaclates into a new strand, the replication of newstrand after intercalating agent loss will result in deletion mutation. Proflavin could revert the muatation caused by the compound 2 that means the mutation caused by compound 2 can be deletion or insertion mutation.

Compound 3: 5-Bromouracil,EMS, proflavin and hydroxylamine could revert the mutation caused by compound 3.That means compound 3 can induce several different muatational pathways. (As explained for compound 1) As the mutation by compound 3 is reverted by 5-Bromouracil and EMS, compound 3 could cause a point mutation. Simillarly, (as explained for compound 2) as the mutation caused by compound could be reverted by proflavin, compound 3 could also cause a deletion or insertion mutation. Hydroxylamine is a base modifying agent, which modifies a base. Hydroxylamine reacts only with cytosine andd add a hydroxyl group(-OH) to cytosine.This modified cytosine pairs with adenine instead of guanine(resulting in transition of nucleotide), and leading to a point mutation. In summary the compound 3 causes a point mutation and a insertion(or deletion mutation) which was reverted by 5-Bromouracil,EMS, proflavin and hydroxylamine.

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