Genomic DNA from a child with pyruvate kinase deficiency identifies a mutation in the 3'-splice site of intron 3. The mRNA from the child's reticulocytes is used to produce cDNA. Primers flanking the exon 3/exon 4 border are used to amplify this region from the cDNA (RT-PCR). The products are separated by electrophoresis and compared to the RT-PCR products from normal reticulocytes (control). The results are shown below: Control shows 84 bp band, Patient shows 78 bp band. Which of the following mechanisms best accounts for the results of the splice mutation?

1. A)Trinucleotide expansion
2. B)Exon skipping
3. C)Missense mutation
4. D)Two-codon deletionGABARITO
5. E)Frameshift mutation