Module 1 : Introduction

QUIZ-1

Q5: A 500 bp long DNA sample was digested using two restriction enzymes. The digested DNA products were analyzed using gel electrophoresis as shown below:

Map the restriction sites for the two enzymes in the DNA molecule

Ans: Digestion with restriction enzyme-1 gives two bands of sizes 200 bp and 300 bp. This results in following two possibilities:

Digestion with restriction enzyme-2 gives two bands of sizes 350 bp and 150 bp:

Digestion with both restriction enzymes-1 and 2 gives two bands of sizes 200 bp and 150 bp. The possible restriction maps from the given data are: (A+D) and (B+C) i.e.

The combinations, (A+B), (A+C), (B+D), and (C+D) do not fit the given data.

 

Q6: Trypsin is one of the most commonly used proteases for generating peptide fragments for mass spectrometric analysis.

  1. What are the cleavage sites for trypsin in a polypeptide chain?
  2. Name a protease that cleaves at the carboxyl end of the aromatic amino acids.

Ans:

  1. Trypsin leaves at the carboxyl end of arginines and lysines.
  2. Chymotrypsin cleaves at the carboxyl end of the aromatic amino acids.