Abstract: Chromosome XV was one of the last
two chromosomes of Saccharomyces cerevisiae to be discovered. It is
the third-largest yeast chromosome after chromosomes XII and IV,
and is very similar in size to chromosome VII. It alone represents
9\\\% of the yeast genome (8\\\% if ribosomal DNA is included). When
systematic sequencing of chromosome XV was started, 93 genes or markers
were identified, and most of them were mapped. However, very little
else was known about chromosome XV which, in contrast to shorter
chromosomes, had not been the object of comprehensive genetic or molecular
analysis. It was therefore decided to start sequencing chromosome
XV only in the third phase of the European Yeast Genome Sequencing
Programme, after experience was gained on chromosomes III, XI and II. The
sequence of chromosome XV has been determined from a set of partly
overlapping cosmid clones derived from a unique yeast strain, and
physically mapped at 3.3-kilobase resolution before sequencing. As
well as numerous new open reading frames (ORFs) and genes encoding
tRNA or small RNA molecules, the sequence of 1,091,283 base pairs
confirms the high proportion of orphan genes and reveals a number of
ancestral and successive duplications with other yeast chromosomes.
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