The dystrophin gene is the largest known gene in the human
genome with its 79 exons spanning over 2Mb of genomic DNA.
The mRNA is 14kb, encoding a protein of 3685 amino acids.
Mutations in this human X-linked gene are responsible for the
allelic disorders Duchenne (DMD) and Becker (BMD) muscular
dystrophies. Introns comprise a huge proportion of the gene.
The large intron size is not unique to the human dystrophin gene
but has also been observed in other vertebrates, suggesting
some functional relevance. We are analysing the dystrophin
gene in an Australian marsupial (tammar wallaby) and an
American species (Brazilian grey short-tailed opossum) by
sequencing the ~14kb tammar transcript, creating a BAC contig
of the tammar locus and using the data available from the
opossum genome sequencing project. Our analysis has revealed
that the marsupial dystrophin gene also spans some 2Mb
genomic DNA. Intron sizes are maintained in marsupials and
many conserved intragenic sequences have been identified that
may represent control sequences. This supports the idea that
introns have a functional role in the dystrophin gene.