English: (A) The probability for a contiguous gene, say 70 nucleotides long, is 4-70. The length of the random sequence in which it is expected to occure once is 10^42 nucleotides. (B) In contrast, when this gene is split into many exons , say 5 exons with 17, 10, 9, 20 and 15 nucleotides consecutively, the probability for the gene is essentially that of the longest exon (20 nucleotides). The probability for this split gene is thus 4^-20 and its expected mean length is reduced tremendously to 10^12 nucleotides.