Section 10 — Developmental Genetics 



biosynthesis); therefore, in the hope of restoring 

 normal folic acid metabolism and fertility, dor 

 females were made homozygous for ry, ry 2 and 

 bw; ry lacks isoxanthopterin (accumulated by dor 

 females: Counce, 1957); bw lacks all the pterins; 

 dor, bw females remained sterile; dor, ry or ry 2 

 flies were lethal indicating that the type of inter- 

 action sought may have occurred, although in an 

 unexpected direction. 



10.4. Genetic and Physiological Studies of Abnormal 

 Abdomen in Drosophila melanogaster. Ralph 

 Hillman, and Stephen D. Barbour (Philadel- 

 phia, U.S.A.). 



Abnormal abdomen was first described by 

 T. H. Morgan in 1915 as one of the earliest cases 

 in which the environment controlled the pene- 

 trance and expressivity of a genetic factor. This 

 original mutation was subsequently lost. In 1953, 

 Hillman W reported a recurrence of this ab- 

 normality as a result of X-irradiation. The 

 mutation A53g exhibits environmental relation- 

 ships similar to the original abnormal abdomen 

 and is located in the same approximate position 

 as that reported by Morgan. Recent genetic in- 

 formation indicates that A$3g acts as a cross-over 

 suppressor of the left end of the X-chromosome. 

 Cytological studies have shown a rearrangement 

 of the banding pattern in the heterozygous A53gj 

 Canton-S salivary chromosomes involving two 

 to five bands in the 3C-3D region of the X- 

 chromosome. 



Preliminary chromatographic studies of the 

 amino acid constituents of the mutant stock have 

 yielded a possible explanation of the morpho- 

 logical effects. Since only the adult abdominal 

 hypoderm and tergites are abnormal in A53g, 

 individual prepupae have been squashed on 

 Whatman-1 paper and developed in butanol — 

 acetic acid — water. Results with general and 

 specialized indicators show an apparent increase 

 in the glutamic acid concentration of A53g and a 

 decrease in staining of the spots corresponding to 

 glutamine and proline. Since proline is known to 

 be an important constituent of the hypodermal 

 protein and glutamine is on the metabolic path- 

 way from glutamic acid to glucosamine and 

 chitin, these results are suggestive of an upset in 

 glutamic acid metabolism as a cause of the 

 morphological abnormalities. 



10.5. A Cytochemical Analysis of Deoxyribonucleic 

 Acid (DNA) and Protein in Salivary Gland 

 and Gut of the Lethal Mutant lgl of D. melano- 

 gaster. Robert M. Welch and Kathleen 

 Resch (Austin, U.S.A.). 



Previous research, comparing mature lgl with 

 mature wild-type larva, has suggested a differen- 

 tial effect, notably on salivary gland in compari- 

 son with gut and on DNA of salivary gland in 

 comparison with protein. An alternative expla- 

 nation, however, is differential growth in wild- 

 type larva after onset of general retardation in lgl. 

 To decide between these two interpretations, 

 DNA and protein in sections of salivary gland, 

 proventriculus, and stomach of mature lgl have 

 been compared with corresponding compounds 

 of wild-type larva at a stage where lgl DNA is 

 approximately equal to wild-type DNA and 

 where lgl salivary gland is approximately equal 

 to wild-type salivary gland. Gland and gut areas 

 have also been determined. Also, wild-type 

 larvae, experimentally altered in DNA or protein 

 metabolism, have been compared with normal. 

 DNA has been determined by Feulgen cyto- 

 photometry, protein by naphthol yellow S 

 cytophotometry and photometric interferometry. 

 Results do not indicate increased synthesis of 

 protein over DNA in lgl in either salivary gland 

 or gut at stages compared, nor increased growth 

 of gut in comparison with salivary gland. 

 Therefore, they do not support the hypothesis 

 of a differential effect, either chemical or organ, 

 of the mutation in lgl, although results on ex- 

 perimentally altered larvae do not exclude a 

 differential effect on DNA, affecting protein 

 synthesis indirectly. In absence of contrary 

 evidence, however, results suggest that differen- 

 tial growth of wild-type larva after a stage of 

 general retardation in lgl has produced the 

 appearance of a differential effect in mature lgl 

 when compared with mature wild-type larva. 



1. DIS 27, 56. 



Supported (in part) by PHS Research Grant 

 GM-06492 from the National Institutes of 

 Health, USPHS, and by a grant from the Rocke- 

 feller Foundation. 



10.6. Gene Action of esc (extra sex comb) in 

 Drosophila melanogaster. Chiyoko Tokunaga 

 (Berkeley, U.S.A.). 



When homozygous, the esc gene (II L) initiates 

 the morphological change of the second and 

 third male legs into a first leg in terms of bristle 

 pattern which includes differentiation of an extra 



170 



