J. Locke et al., A physical map of the polytenized region (101EF-102F) of chromosome 4 in Drosophila melanogaster, GENETICS, 155(3), 2000, pp. 1175-1183
Chromosome 4, the smallest autosome (similar to 5 Mb in length) in Drosophi
la melanogaster contains two major regions. The centromeric domain (similar
to 4 Mb) is heterochromatic and consists primarily of short, satellite rep
eats. The remaining similar to 1.2 Mb, which constitutes the banded region
(101E-102F) on salivary gland polytene chromosomes and contains the identif
ied genes, is the region mapped in this study. Chromosome walking was :hind
ered by the abundance of moderately repeated sequences dispersed along the
chromosome, so we used many entry points to recover overlapping cosmid and
BAC clones. rn situ hybridization of probes from the two ends of the map to
polytene chromosomes confirmed that the cloned region had spanned the 101E
-102F interval. Our BAC clones comprised three contigs; one gap was positio
ned distally in 102EF and the other was located proximally at 102B. Twenty-
three genes, representing about half of our revised estimate of the total n
umber of genes on chromosome 4, were positioned on the BAC contigs. A minim
al ti:ling set of the clones we have mapped will facilitate both the assemb
ly of the DNA sequence of die chromosome and a functional analysis of its g
enes.