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

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186<br />

Figure 11.1<br />

Some fundamentals of gene expression.<br />

mRNA = messenger RNA, tRNA = transfer RNA,<br />

rRNA = ribosomal RNA.<br />

Part II The Applications of <strong>Gene</strong> <strong>Cloning</strong> <strong>and</strong> <strong>DNA</strong> <strong><strong>An</strong>alysis</strong> in Research<br />

(a) <strong>Gene</strong>s are expressed by transcription <strong>and</strong> translation<br />

RNA<br />

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

(b) Some genes contain introns<br />

Introns<br />

Transcription<br />

Transcription<br />

(c) RNA transcripts include regions either side of the gene<br />

Start signal for<br />

transcription<br />

Translation of mRNA<br />

Protein<br />

Processing<br />

Translation<br />

Protein<br />

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

11.1 Studying the RNA transcript of a gene<br />

<strong>DNA</strong> molecule<br />

RNA<br />

rRNA, tRNA<br />

<strong>DNA</strong> molecule<br />

Primary RNA transcript<br />

– still contains introns<br />

Mature RNA –<br />

no introns<br />

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

End signal<br />

Over the years a variety of techniques have been devised for studying RNA transcripts.<br />

Some of these techniques merely detect the presence of a transcript <strong>and</strong> give some<br />

indication of its length, others enable the start <strong>and</strong> end of the transcript to be mapped<br />

<strong>and</strong> the positions of introns to be located.<br />

11.1.1 Detecting the presence of a transcript <strong>and</strong> determining<br />

its nucleotide sequence<br />

Before studying the more sophisticated techniques for RNA analysis, we must consider<br />

the methods used to obtain basic information about a transcript. The first of these<br />

methods is northern hybridization, the RNA equivalent of Southern hybridization

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