<P> A splice site mutation is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA . Splice site consensus sequences that drive exon recognition are located at the very termini of introns . The deletion of the splicing site results in one or more introns remaining in mature mRNA and may lead to the production of abnormal proteins . When a splice site mutation occurs, the mRNA transcript possesses information from these introns that normally should not be included . Introns are supposed to be removed, while the exons are expressed . The mutation must occur at the specific site at which intron splicing occurs: within non-coding sites in a gene, directly next to the location of the exon . The mutation can be an insertion, deletion, frame shift, etc . The splicing process itself is controlled by the given sequences, known as splice - donor and splice - acceptor sequences, which surround each exon . Mutations in these sequences may lead to retention of large segments of intronic DNA by the mRNA, or to entire exons being spliced out of the mRNA . These changes could result in production of a nonfunctional protein . An intron is separated from its exon by means of the splice site . Acceptor - site and donor - site relating to the splice sites signal to the splicesome where the actual cut should be made . These donor sites, or recognition sites, are essential in the processing of mRNA . The average vertebrate gene consists of multiple small exons (average size, 137 nucleotides) separated by introns that are considerably larger . </P> <P> In 1993, Richard J. Roberts and Phillip Allen Sharp received the Nobel Prize in Physiology or Medicine for their discovery of "split genes". Using the model adenovirus in their research, they were able to discover splicing--the fact that pre-mRNA is processed into mRNA once introns were removed from the RNA segment . These two scientists discovered the existence of splice sites, thereby changing the face of genomics research . They also discovered that the splicing of the messenger RNA can occur in different ways, opening up the possibility for a mutation to occur . </P>

What effect could mutations in splice sites have on protein production
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