Glossary

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Splicing

In higher organisms: cutting out specific areas of messenger RNA

Many genes in higher organisms occur in fragmented form, i.e. the gene sequence is interrupted by segments of DNA which do not encode a blueprint for proteins. The areas containing biological information are referred to as exons (expressed sequences), whilst the sections in between are called introns (intervening sequences).

The process of transcribing genetic information into proteins starts by making an RNA copy of the entire gene sequence (see transcription). This is referred to as a primary transcript (pre-mRNA). The introns are then removed and the exon sequences are joined together by means of a complex regulatory mechanism. This process is referred to as splicing. The now completed mRNA then travels to the ribosomes, where it is translated into an amino acid chain (protein).

Sometimes during the splicing process the exons can recombine in different ways (‘alternative’, ‘differential’ or ‘tissue-specific splicing’). This means that a large number of different proteins can be produced from a single gene section. The dscam gene of the fruit fly Drosophila currently holds the record with 38,016 different proteins.