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Electrophoretic Variants of
a-Glycerophosphate Dehydrogenase
in Drosophila melanogaster
Abstract. Two alleles of Gdh, the
locus specifying the electrophoretic mobility of a-glycerephosphate dehydrogenase, are found in Drosophila melano-
gaster. The gene is located on the sec-
ond chromosome at a map position of
17.8. Hybrid enzyme molecules are
found in heterozygotes.
The enzyme aq-glycerophosphate de-
hydrogenase (GDH) catalyzes the oxi-
dation of «-glycerophosphate to dihydroxyacetone phosphate and the reverse
reaction. Extraordinarily high activity
of this enzyme is found in thoracic
muscle of insects (7, 2), where it plays
an important role in the rapid production of energy from carbohydrate
[see reviews by Sacktor (3) and Chef-
urka (4)].
Electrophoretic variants of at least
12 enzymes are known in Drosophila
melanogaster
[see
review by Shaw
(5)]. More than one electrophoretic
type of an enzyme is more the rule
Fig. 2. Globigerina bulloides (d’Orbigny); Recent, Scotian Shelf at 50 m. Note
narrow elongate spines over entire surface, concentration of spines in apertural
region, and absence of any form of bilamellar or secondary thickening (x 400).
The secondary layers can be counted
by focusing on individual pores. Both
bilamellar
and
secondary
thickening
support the hypothesis (3) that shell
thickening occurs at depth in adult
stages of planktonic Foraminifera. Spinal development in G. bulloides at
depth is contrary to findings of Bé
and Hamlin (4), who found spines only
in juveniles living at or near the surface of the ocean.
I have also investigated differences
in microstructure of other foraminiferal
species
(5).
Globoquadrina dehiscens
dehiscens (Chapman, Parr, and Collins) differs radically from Globigerina
in wall structure as well as in having
prominent apertural flaps covering each
aperture. Globigerinoides trilobus trilobus (Ruess) displays a heavy cancel-
late pore pattern, characteristic of
the Globigerinoides group. However,
Globigerinoides trilobus immaturus LeRoy, considered by many to be a member within the G, trilobus (s.1.) evolutionary sequence, has a surface cov-
ered with irregularly spaced knobs and
small circular pores; this wall structure resembles that of Globigerina.
I have mentioned only a few morpho8 DECEMBER 1967
logic characteristics. Many detailed features of various microorganisms, hither-
to unavailable, are being investigated
and will now add greatly to the determination of evolutionary sequences
and specific. generic, and familial relations; they will enable more natural
than the exception in this species. The
genetic loci responsible for the variations have in most cases been located
on the linkage map of Drosophila.
A method for acrylamide gel electrophoresis of a-glycerophosphate dehydrogenase of Drosophila has been
described by Sims (6). Hubby and
Throckmorton (7) examined GDH
electrophoretic patterns of several spe-
cies of the virilis group of Drosophila
and found differences between but not
classification of these microorganisms.
This new insight can be attributed to
the scanning electron microscope.
GRANT A. BARTLETT
Micropaleontology, Bedford Institute
of Oceanography, P.O. Box 1006,
Dartmauth, Nova Scotia
References and Notes
1.C. W. Oatley, Sci. Progr. Oxford 54, 483
(1966);
, W. C, Nixon, R. F. W. Pease,
Advan. Electron. Electron Phys. 21, 181
(19653; T. L. Hayes, R. F. W. Pease, L. W.
McDonald. Lab. Invest. 15, 1320 (1966).
2, R. F. W. Pease, T. L. Hayes, A. S. Camp,
N. M. Amer, Science 154, 1185 (1966).
3. A. W. H. Bé, Micrapaleontology WU, 1 (1965);
and L, Lott, Science 145, 823 (1964);
A. W. H. Bé, A. Mcintyre, D. L. Breger,
Ecol. Geol, Helv. 89, 2 (1966).
4. A. W. H. Bé and W. H. Hamlin, Micropaleontology, 13, 1, 87 (1967).
5. G. A. Bartlett, Can. J. Earth Sei., in press.
6. I thank Charles Godden, Marine Geology
Division, Bedford Institute of Gceanography,
for his active interest and the photographs
{taken with the aid of the Jeoleo scanning
electron microscope: Jeolco (U.S.A.) Inc.,
477 Riverside Drive. Medford. Mass.].
2! August
1967
convear corvcar® —carPoar?
Fig. 1. Acrylamide-gel electrophoresis of
- a-glycerophosphate
dehydrogenases
of
Drosophila melanogaster. On the left is
the homozygote of the rapid type of GDH.
On the right is the homozygote of the
slow type of GDH. In the center are two
heterozygotes of the two alleles.
1319