Chapter 11, Problem 1P

Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book.

Predicting a Sanger Sequencing Pattern The oligonucleotide d-AGATGCCTGACT as subjected to sequencing by Sanger’s dideoxy method, using fluorescent-tagged dideoxynucleotides and capillary electrophoresis, essentially as shown in Figure 11.3. Draw a diagram of the gel-banding pattern within the capillary.

Interpretation Introduction

Interpretation: A diagram of the gel-banding pattern within the capillary is to be drawn.

Concept introduction: A laboratory technique that is used for the separation of charged molecules such as proteins, DNA and RNA on the basis of their size is known as gel electrophoresis. This technique is useful to distinguish DNA fragments of various lengths.

Answer to Problem 1P

A diagram of the gel-banding pattern within the capillary is,

  

Explanation of Solution

In gel electrophoresis, using dyes such as radioactive labels or fluorescent tags makes it possible to see the DNA on the gel after separation. They are going to appear on the gel as bands. Therefore, the fluorescently labeled dideoxynucleotides result in the formation of the gel banding pattern. The labeled dideoxynucleotides are then added to the growing chain of DNA and capillary electrophoresis is applied to the resulting fragments.

The given oligonucleotide is d-AGATGCCTGACT that was subjected to sequencing by Sanger’s dideoxy method. In gel-banding pattern within the capillary, the top of the column consists of larger fragments and the bottom of the column has smaller fragments. The $3^{\text{'}}$ end is present at the top of the column because the larger fragments have more nucleotides and the $5^{\text{'}}$ end is at the bottom of the column. Hence, the diagram of the gel-banding pattern within the capillary is shown below.

  

  Figure 1