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Gene Cloning and DNA Analysis: An Introduction, Sixth Edition ...

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Chapter 11 Studying <strong>Gene</strong> Expression <strong>and</strong> Function 201<br />

Figure 11.21<br />

Hybridized<br />

mRNA cannot<br />

be translated<br />

Protein coded<br />

by the c<strong>DNA</strong><br />

<strong>Gene</strong><br />

Properties of the<br />

normal protein<br />

mRNA preparation<br />

Protein<br />

Add specific<br />

c<strong>DNA</strong><br />

Cell-free<br />

translation<br />

HART products Total translation<br />

products<br />

Compare<br />

c<strong>DNA</strong> hybridizes<br />

to the mRNA<br />

counterpart<br />

Gel electrophoresis,<br />

autoradiography<br />

Mutation, e.g. T A<br />

*<br />

Properties of the<br />

mutated protein<br />

Figure 11.20<br />

Hybrid-arrest translation.<br />

* Mutation, e.g. ile leu<br />

A mutation may change the amino acid sequence of a protein, possibly affecting its properties.<br />

protein <strong>and</strong> its mode of activity. The best way of tackling these problems is to induce a<br />

mutation in the gene coding for the protein <strong>and</strong> then to determine what effect the<br />

change in amino acid sequence has on the properties of the translation product<br />

(Figure 11.21). Under normal circumstances mutations occur r<strong>and</strong>omly <strong>and</strong> a large<br />

number may have to be screened before one that gives useful information is found. A<br />

solution to this problem is provided by in vitro mutagenesis, a technique that enables<br />

a directed mutation to be made at a specific point in a cloned gene.

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