Synthesis of the amino acid histidine is a multistep ana...

Question

Synthesis of the amino acid histidine is a multistep anabolic pathway that uses the products of 13 genes (hisA to hisM) in E. coli. Two independently isolated E. coli mutants, designated his1⁻ and his2⁻ are studied in a conjugation experiment. A his⁺ F' donor strain that carries a copy of the hisJ gene on the plasmid is mated with a his1⁻ recipient strain in Experiment 1 and with a his2⁻ recipient in Experiment 2. The exconjugants are grown on plates lacking histidine. Growth is observed among the exconjugants of Experiment 2 but not among those of Experiment 1.

What is the genotype of exconjugants in Experiment 2?

Accepted Answer

Hello everyone and welcome to today's video. So in an experiment, two bacterial strains were used strain A which contains genes for prolene but not for arginine and strain B which contains gene for arginine but not for pro. So when the two strains were mixed in a culture medium, lacking arginine and prolene, no growth was observed. However, when a small amount of arginine and prolene was added to the medium growth was observed. So a third strain C was also used in the, in the experiment which does not contain genes for arginine or prolene based on these results which of the following statements are therefore true. As answer choice A, we have strain A can synthesize prole but not arginine. As answer choice B, we have strain B can synthesize arginine but not prone as answer choice C. We have string C is unable to synthesize either arginine or protein. And as answer choice D, we have all options are correct. Well, before we jump into the answer choices and start analyzing them, remember that we have this medium that does not contain proline or A. So when the bacteria were present in this medium that did not contain neither prolene or arginine. They were not able to grow, none of the three strains were able to grow although they had genes that coated for some of these. However, when we added rolling and arginine growth was observed. So what does this mean? Let's go over into our answer choices so that we may solve the problem as answer choice. A we have strain A can synthesize prole but no arginine. Well, remember that this strain is going to have the genes for prole but not for arginine. And because of this, we can conclude that they can synthesize prole and no arginine. This is a correct statement. So we're not going to cancel it out. Then we have B string B can synthesize arginine but no proin here we have the same thing. This string contains the genes for arginine, it's arginine positive but for pro it does not. So it's the opposite as strain. This is a correct statement as well. So we're not going to cancel it out. Then we have strain C is unable to synthesize either arginine or protein. If we look at the information for the genetics of the bacteria that we are provided, strain C is stated to be negative for arginine and pro so it cannot synthesize on either of these. So these strains are oxo traffic for some of these nutrients, meaning that they won't be able to grow if both of them are not present because of this, this is also a correct statement and we're not going to cancel it out since we're not able to cancel out any of the statements in the question, we're going to highlight answer choice. D all options are correct. As a final answer. I really hope this video helped you and I hope to see you on the next one.

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