ORF

The presence of open reading frames (ORF),
transcripts, exons, and polyadenylated sites in
this region indicates that one is dealing with a
gene. Such stretches of DNA most likely representing
genes are isolated and subjected to mutational
analysis (6). Those genes not containing
mutations in patients can be excluded (7).
When mutations are found and a polymorphism
is excluded, the correct gene has been
identified (8). For confirmation, the expression
pattern is analyzed, its structure (exons, introns)
and size are determined, the transcript is
analyzed, and these properties are compared
with those of similar genes in other organisms
(“zoo blot”, see p. 250). Finally, the DNA
sequence of the entire gene can be determined
and conclusions about the function drawn.
From here on, a gene-directed diagnostic procedure
can be developed.