| PubMed Abstract |
The analysis of patterns of genome evolution may help to evaluate the evolutionary forces that shape the composition and organization
of the genome. Comparisons between the physical maps of divergent species can be used to identify conserved blocks of closely
linked genes whose synteny is possibly under selective constraint. We have used in situ hybridization to determine the genomic
position of 732 randomly selected clones from a bacteriophage P1 library of Drosophila virilis. The resulting map includes
at least one clone in each of 69% of the subdivisions into which the D. virilis polytene chromosomes are divided. A subset
of these clones was used to carry out a comparative physical analysis of chromosome 2 from D. virilis and from Drosophila
montana. A number of discrepancies with the classical scenario of chromosome evolution were noted. The D. virilis P1 clones
were also used to determine the physical relations between ten genes that are located in the X chromosome of Drosophila melanogaster
between the markers crn (2F1) and omb (4C5-6). In this region, which is approximately 2 Mb in length, there have been at least
six breakpoints since the divergence of the species, and six of the genes are found at widely scattered locations in the D.
virilis X chromosome. However, a block of four functionally unrelated genes, including white, roughest, Notch, and dunce,
seems to be conserved between the two species.
|
Home
Associated Information