what is the biochemical basis for affinity purification of a recombinant protein using a 6X his tag and nickel chelate ?

28. In a transformation experiment, DNA is collected from an E. coli donor strain of genotype cys(+) leu(-) thr(+) and used to transform a recipient of genotype cys(-) leu(+) thr(-). Initially, the treated recipient population is plated on a minimal medium supplemented with threonine. Many colonies are obtained. What are possible genotypes of these colonies? A. cys(-) leu(+) thr(+) B. cys(+) leu(+) thr(-) C. All are cys(+) and either + or - for leu and thr D. All are thr(+) and either + or - for cys and leu E. All are thr(-) cys(-) and either + or - - for CYS

To determine the reproducibility of mutation fre-quency measurements, you do the following experiment.You inoculate each of 10 cultures with a single E. coli bac-terium, allow the cultures to grow until each contains 106cells, and then measure the number of cells in each culturethat carry a mutation in your gene of interest. You were sosurprised by the initial results that you repeated the experi-ment to confirm them. Both sets of results display the sameextreme variability, as shown in Table Q5–1. Assuming thatthe rate of mutation is constant, why do you suppose thereis so much variation in the frequencies of mutant cells indifferent cultures?

Can you give an example of a modified (tagged) primers to amplify E. coli UidA sequence and subclone into appropriate vector (pUC19)?