Using a cDNA library, you isolated two different cDNA clones that have sequences indicating that they both correspond to mRNAs transcribed from the same nerve growth factor gene. The beginning and ending sequences of the clones are the same, but the middle sequence is different. How can you explain the differ- ent cDNAs

These two cDNA clones are different splicing products from the same precursor mRNA

Explanation:

Alternative splicing is a common process in eukaryotic organisms that enables the same gene to produce two or more protein variants. During transcription, the gene is first transcribed into a precursor mRNA (pre-mRNA) which contains exons and introns. Subsequently, during alternative splicing, introns are removed while exons are differentially joined or skipped in order to form the final mRNA coding sequence. Consequently, different mature mRNA sequences may be produced from the same primary mRNA transcript depending on which exons are joined or skipped. Finally, it is important to indicate that a cDNA clone is a DNA sequence produced after reverse transcription from a specific messenger RNA template.

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