In an experiment similar to the Lederberg and experiment, researchers grow two s

Question

In an experiment similar to the Lederberg and experiment, researchers grow two strains of E. coli in complete medium. E. coli strain AX has the genotype Amp^S bio + trp+ leu. E. coli strain AY has the genotype Amp^R bio- trp-leu^+. The researchers then plated the bacteria on different media types. Next, the researchers mixed equal amounts of the AX and AY E. coli strains. On which type(s) of media would growth provide evidence that genetic transfer had occurred between the two strains of bacteria? Select all that apply. bio-leu- bio-trp- trp-leu- leu-trp-bio- none of the above

Explanation / Answer

Answer:

Ecoli Strain AX AmpSbio+ trp+ leu- : This strain will grow if the media is supplemented with leucine and without the presence of Ampicillin

Ecoli Strain AY AmpRbio- trp- leu+ :This strain will grow if media is supplemented with Biotin and Tryptophan and this strain can also grow in presence of Ampicillin antibiotic as it is resistant to it.

If the genetic transfer has happened after mixing the two strains:

1) bio- leu- : growth in this media will provide evidence that genetic transfer has taken place, because only if the genetic transfer the taken place the strain will have genotype bio+ leu+ and can grow in media without additional biotin and leucine.

2) bio- trp- : Using this media, we wont be able to infer if the genetic transfer has taken place, because Strain AX is bio+ trp+ that means, this strain is capable of growing in a media which doesnot have added biotin and tryptophan. So even if genetic transfer doesnot happen, strain AX alone can still grow in this media.

3) trp- leu- : This case is similar to first case, in this media also we can determine if genetic transfer has taken place, because only if the genetic transfer the taken place the strain will have genotype trp+ leu+ and can grow in media without additional tryptophan and leucine.

4) leu- trp- bio-: In this case also media can be used to determine if the genetic transfer has taken place, because genetic transfer would lead to genotype bio+ trp+ leu+ and this strain can grow in the absence of leucine tryptophan and biotin in the media.

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