-
Identify the correct statement for the ‘HAT medium’
(P) Includes drug aminopterin to block major pathway for synthesis of deoxyri-bonucleotides
(Q) Hypoxanthine is precursor for thymidine
(R) Includes drug aminopterin to block major pathway for synthesis of polypeptides
(S) Cells can grow in presence of aminopterin only if they have enzymes thymidine kinase and hypoxanthine-guanine phosphoribosyl transferase
-
- P, Q
- P, S
- R, S
- Q, S
Correct Option: B
STATEMENT P : HAT Medium (hypoxanthine-aminopterin-thymidine medium) is a selection medium for mammalian cell culture, which relies on the combination of aminopterin, a drug that acts as a powerful folate metabolism inhibitor by inhibiting dihydrofolate reductase, with hypoxanthine and thymidine which are intermediates in
DNA synthesis. Aminopterin blocks DNA de novo synthesis.
STATEMENT S : The thymidine present in the HAT medium that can be absorbed by the cells and phosphorylated by thymidine kinase (TK) into TMP. By additional phosphorylation reactions, TMP can be used to make thymidine triphosphate (TTP), one of the four nucleotide precursors that are used by DNA polymerases to create DNA. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) reacts with hypoxanthine absorbed from the medium with PRPP, liberating pyrophosphate, to produce IMP(Inosine Mono Phosphate) by a salvage pathway.
Therefore, the use of HAT medium for cell culture is a form of artificial selection for cells containing working TK and HGPRT.
