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

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216<br />

Figure 12.11<br />

Serial analysis of gene expression (SAGE).<br />

Figure 12.12<br />

Microarray analysis. The microarray shown here<br />

has been hybridized to two different c<strong>DNA</strong><br />

preparations, each labelled with a fluorescent<br />

marker. The clones which hybridize with the<br />

c<strong>DNA</strong>s are identified by confocal microscopy.<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 />

5’<br />

mRNA<br />

cRNA<br />

3’<br />

5’<br />

3’<br />

TTTT<br />

Oligo (dT) str<strong>and</strong><br />

Discard the<br />

end fragment<br />

Hybridize with<br />

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

Hybridization detected by<br />

confocal microscopy<br />

Cellulose<br />

bead<br />

Add RNA<br />

Collect, ligate to other<br />

fragments, sequence<br />

Microarray<br />

TTTT<br />

AAAA<br />

Convert to doublestr<strong>and</strong>ed<br />

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

Digest with AluI<br />

TTTT<br />

AAAA<br />

TTTT<br />

AAAA<br />

Ligate linker<br />

containing BamFI sequence<br />

TTTT<br />

AAAA<br />

Digest with BamFI<br />

TTTT<br />

AAAA<br />

Hybridization<br />

signals<br />

examining the microarrays by confocal microscopy. Those spots that gave a signal<br />

indicated genes that were active under the conditions being studied, <strong>and</strong> the intensities<br />

of the hybridization signals revealed the relative amounts of the mRNAs in the<br />

transcriptome. Changes in gene expression, when the yeast were transferred to different<br />

growth conditions (e.g., oxygen starvation), could be monitored by repeating the<br />

experiment with a second c<strong>DNA</strong> preparation.<br />

Microarrays are now being used to monitor changes in the transcriptomes of many<br />

organisms. In some cases the strategy is the same as used with yeast, the microarray representing<br />

all the genes in the genome, but this is possible only for those organisms that

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