A dilution of a microbial culture was prepared by adding 1 mL of the culture to 9 mL of sterile blank. Further, 200 μL from the diluted culture was…
A dilution of a microbial culture was prepared by adding 1 mL of the culture to 9 mL of sterile blank. Further, 200 μL from the diluted culture was spread on an agar plate; and 150 colonies were observed after the incubation period. Calculate the CFU/mL of the original sample.
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Correct Answer: Option B
Explanation
-P-ATP contains the radioactiveP label on the TERMINAL (gamma) phosphate group. T4 Polynucleotide Kinase (PNK) transfers the-phosphate of ATP to the 5'-OH end of DNA or RNA, creating a 5'-P-labelled end (end-labelling). This is used to label oligonucleotides or restriction fragments for: gel shift assays (EMSA), footprinting, sequencing by Maxam-Gilbert method, and probe preparation. In contrast: Nick translation uses-P-dNTPs (the label goes into the phosphodiester backbone of the new strand). Reverse transcription uses-P-dNTPs. The-phosphate is unique in that it becomes the TERMINAL phosphate after the kinase reaction — therefore-P-ATP is ONLY useful for end-labelling (not nick translation or reverse transcription).