In the mating Hfr Strs met+ his+ leu+ trp+ Ala+   X F- Strres met- his- leu- trp- Ala-. At regular interval time, the mating cells are interrupted and the cell suspensions plated on four different growth media with streptomycin. The amino acids in the growth media and the number of colonies observed on each are as follows:

Interrupted time	Composition of media					Growth
	His	Leu	Ala	Trp	Met
2   min	+	-	+	+	+	Yes
10 min	+	-	-	+	+	Yes
12 min	+	-	-	+	-	No
15 min	+	-	-	-	+	Yes
20 min	-	-	-	-	+	Yes

What is the order of transfer of the genes?

#Question id: 174

#Unit 1. Molecules and their Interaction Relevant to Biology

What is the net charge on the dipeptide Arg-Pro at pH 9.0? The table below gives the pKaʹs of the ionizable groups on the free amino acids.

#Question id: 175

#Unit 1. Molecules and their Interaction Relevant to Biology

The ionic charges associated with a protein molecule are ________.

#Question id: 176

#Unit 1. Molecules and their Interaction Relevant to Biology

A peptide has the sequence Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly. What is the net charge of the molecule at pH 3

#Question id: 176

#Unit 1. Molecules and their Interaction Relevant to Biology

A peptide has the sequence Glu–His–Trp–Ser–Gly–Leu–Arg–Pro–Gly. What is the net charge of the molecule at pH 3

#Question id: 177

#Unit 1. Molecules and their Interaction Relevant to Biology

The titration curve of alanine shows the ionization of two functional groups with pKa values of 2.34 and 9.69, corresponding to the ionization of the carboxyl and the protonated amino groups, respectively. The titration of di-, tri-, and larger oligopeptides of alanine also shows the ionization of only two functional groups, although the experimental pKa values are different. The trend in pKa values is summarized in the table. Which of the following is a reason for this shift in pK values

#Question id: 178

#Unit 1. Molecules and their Interaction Relevant to Biology

Given the pKa values of different acidic sites in cysteine, the principal ionic form which will never exist at any pH