CDNA cloning

An alternative to cloning genomic DNA, as outlined in the sections above, entails beginning the process not with chromosomal fragments but with mRNA. This is often an approach taken when cloning eukaryotic genes in particular. As described in Figure 3.10, total eukaryotic cellular mRNA can be purified from the cell via an affinity-based mechanism. The mRNAs recovered in this way reflect only the polypeptide-encoding genes that are expressed in the cells at the time of their extraction. Incubation of the mRNA with the enzyme reverse transcriptase results in the conversion of the single-stranded mRNA into double-stranded DNA known as cDNA (see also Figure 3.1). These cDNA fragments can then be cloned to generate a cDNA library, and the desired cDNA clone can be identified by means similar to those already described in the context of cloning genomic DNA. cDNA libraries are smaller than genomic libraries as they are derived only from expressed genes. Non-coding regions in the genome (as well as quiescent genes and genes coding for rRNA and tRNA) are not represented in the library. Therefore, cDNA libraries are more manageable to work with, assuming that the gene of interest is being expressed.

Supplements For Diabetics

Supplements For Diabetics

All you need is a proper diet of fresh fruits and vegetables and get plenty of exercise and you'll be fine. Ever heard those words from your doctor? If that's all heshe recommends then you're missing out an important ingredient for health that he's not telling you. Fact is that you can adhere to the strictest diet, watch everything you eat and get the exercise of amarathon runner and still come down with diabetic complications. Diet, exercise and standard drug treatments simply aren't enough to help keep your diabetes under control.

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