Chapter 13, Problem 22A

a)

Summary Introduction

To determine:

Whether the DNA is circular or linear.

Introduction:

The technique of separating DNA fragments based on their size is termed as gel electrophoresis. In this technique, DNA samples are added to well at the end of the gel. Then, electric current is applied through the gel. As DNA is negatively charged, DNA fragments go towards the positive electrode.

Explanation of Solution

Restriction enzymes cleave the DNA strand at a particular site and form different DNA fragments, that can be similar or different in size. In the given table, it is seen that HindIII restriction enzyme cleave the DNA fragment to give only one DNA fragment of size 3.0 kb. This means that the DNA strand of size 3 kb is circular and HindIII enzyme cleaved it at a point, and converted into a linear DNA fragment of size 3 kb.

b)

Summary Introduction

To draw:

A restriction site map from the given data.

Introduction:

The technique of separating DNA fragments based on their size is termed as gel electrophoresis. In this technique, DNA samples are added to well at the end of the gel. Then, electric current is applied through the gel. As DNA is negatively charged, DNA fragments go towards the positive electrode.

Explanation of Solution

Given information-

EcoRI enzyme cleaves DNA to give two fragments of 1.5 kb and 1.5 kb.

HindIII enzyme cleaves DNA to give one fragment of 3 kb.

Both the above enzymes when act together, cleave DNA to give three fragments of 0.6 kb, 0.7 kb, and 3 kb.

The restriction map for the same is as follows: