A microbiologist is working on delivering nutritional anabolic genes to mutants
ID: 82017 • Letter: A
Question
A microbiologist is working on delivering nutritional anabolic genes to mutants which are defective in three amino acid synthesis processes (genotype of the auxotrophic mutant: trp-, tyr-, his-). After gene delivery, some bacterial colonies can now grow on a certain defined nutritional medium, given in the questions can to below. Please identify what genes that they have acquired to grow, using the choices from #a to #f. a. Tyr+ revertants b. His+ revenants c. Trp+ revertants d. Tyr+, Trp+ revertants e. Tyr+, His+ revertants f. Trp+, His+ revertants The bacterial colonies can now grow in minimal nutritional agar plates with Tyrosine and Histidine amino acids added. The bacterial colonies can now grow in minimal nutritional agar plates with Tyrosine and Tryptophan amino acids added. The bacterial colonies can now grow in minimal nutritional agar plates with Trp amino acids added. A microbiologist delivered his target gene via a viral T4 phage transduction system. This target gene is cloned into a vector containing an Amp+ drug resistant marker. Please answer the following questions to help this microbiologist set up the experiments and screen for positive transductants What type of growth medium should the microbiologist use to select for positive transductants? a. LB/Kanamycin plate b. LB plate c. LB/Ampicillin broth d. LB/Ampicillin plate e. None of the above On the proper selective plates, 50 colonies grew on a "1:100" dilution plate. Estimate around how many colonies would be seen on a "1:10" dilution plate? a. 5Explanation / Answer
The auxotroph requires tryptophan, tyrosine and histidine.
16.
Trp+ revertants
Because they can grow on minimal media supplemented with tyrosine and hisdtidine. They no longer need tryptophan in medium. It means they are able to synthesize tryptophan. It is due to reversion of try- mutation. It was trp- and now it is trp+.
17.
His+ revertants.
It means they are able to synthesize histidine. It is due to reversion of his- mutation.
18.
Tyr+, His+ revertants.
It means they are able to synthesize tyrosine and histidine. It is due to reversion of tyr- and his- mutation.
19.
LB ampicillin agar plate
It will help in selecting ampicillin resistant colonies. Vector has ampicillin resistant gene. So, the transductants would have ampicillin resistant gene.
20.
500 colonies.
1:100 dilution is 10 more dilution of 1:10.
If we get 50 colonies in 1:100, then we should get 50 x 10 = 500 colonies in 1:10.
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