Graphical representation of the Drosophila chromosomes.
Veikko Sorsa (1988 Chromosome Maps of Drosophila, CRC Press) presented
an estimate of the length of DNA of each polytene chromosome lettered
subdivision of Drosophila melanogaster based upon (a) the thickness of
the bands as measured in the electron microscope and (b) a correlation
of 216kb per micron of measured length. Subsequently Sorsa and colleagues
(T.I. Heino and Anja O. Saura) have provided data for each polytene
chromosome band, with the exception of a few bands near the centric
heterochromatin. The graphical map of the chromosomes of D. melanogaster
is made from these data, provided to me as a WingZ file by V. Sorsa,
with corrections to January 4 1993. The data for each band are those given by
Sorsa for a band + interband pair, assuming 5% of the DNA to be interband (ie.
an average interband length of 1.2kb). Because neither the heterochromatin
nor Y chromosome are represented I have added the heterochromatic bands
h1 - h61 as seen in mitotic prophase preparations. Each heterochromatic
band has been given an arbitary length of 100kb (this is a severe under
estimate, of course). The few euchromatic bands close to the chromocenter not
measured by Sorsa have each been given an arbitary length of 25kb. These are:
20D1-2, 20E1-2, 20F1-4; 40D1-5, 40E1-5, 40F1-7; 41A1-3, 41B1-3; 80D1-5,
80E1-3 and 80F1-9. In addition a 'telomere band' has been added to the tip
of each chromosome arm (YLt, YSt, XLt, XRt, 2Lt, 2Rt, 3Lt, 3Rt, 4Lt and 4Rt),
each with an arbitary length of 50kb. 'Centromere bands' have also been added
with an arbitary size of 50kb - Y-cen, X-cen, 2-cen, 3-cen and 4-cen.
Sorsa (1988) identified in the EM several bands not seen by either C.B.
or P.N. Bridges. These bands have not been included in this display -
although they could easily be added should there be a demand.
The data are presented in .ace format.
If these data are publicly used for a graphical display of the Drosophila
chromosomes then the data source should be cited as:
T. I. Heino, A. O. Saura and V. Sorsa, 1994, Salivary gland chromosome
maps. D. I. S.  73:619--738  as modified and compiled by M. Ashburner for
FlyBase.
Michael Ashburner
Cambridge, October 7 1993.