Date of Award:

5-1-1967

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Zoology

Committee Chair(s)

Eldon J. Gardner

Committee

Eldon J. Gardner

Committee

W. S. Boyle

Committee

Datus M. Hammond

Committee

K. L. Dixon

Committee

J. R. Simmons

Committee

J. T. Bowman

Abstract

The tumorous head (tu-h) strain of Drosophila melanogaster is characterized by variable, amorphous or partly organized growths about the adult head, including the eyes, antennae, and facial regions but excluding the mouthparts. No other regions of the body have been found to be affected. The trait is controlled by two major genes, tu-1 on the first chromosome and tu-3 on the third chromosome. Much interest has centered around the nature of the growths. The histologic appearance of the tumor in the adult is already known. Previous attempts had been made to detect the first appearance of the abnormality in the early life stages since a temperature sensitive period exists in the embryo (first 24 hours of life). At the present time the earliest stage at which the abnormality can be detected histologically is immediately after the eversion of the prepupal head which occurs approximately the middle of the life cycle. To test the hypothesis that eversion of the prepupal head is associated with the initiation of development of the tumor in the tu-h strain of D. melanogaster, tu-h eye-antennal discs from late third ins tar larvae were transplanted into tu-h host larvae of similar age (type A transplants). To discover if the tu-h trait is genetically and developmentally autonomous, late third instar tu-h eye-antennal discs were transplanted into late third instar Canton-S hosts (type B transplants). Canton-S is a wild type strain. Since tissue from late third instar larvae was used exclusively, it was possible to learn if the abnormality was determined tissue at that time. The host larvae were allowed to develop to adults and then serial sections were prepared of them in order to study the transplanted tissue. It was convenient to classify the tumorous head adult phenotype into types of tumors to adequately describe their postulated appearance in the transplants. The classification was based on: (a) the location of the tumor with respect to head structures, and (b) the extent of the abnormality. All known types of tu-h expression were included in the classification. Transplanted discs do not generally evert, and are therefore somewhat abnormal; it was necessary to establish criteria for the recognition of the tumor in the transplant. These criteria were designed to eliminate the possibility that artifacts due to the transplantation procedure would be classified as tumors. Also, the criteria specified a particular type of tumor in the transplant which clearly resembled the same type (by the phenotypic classification) found in the adult. Using these criteria and classification together, it was possible to designate some transplants of type A as those that had specific types of tumors. Also, in some of the transplants of type B, tumors were observed. The control transplants, type C, in which the host and the donor were both wild-type (Canton-S), had no tumors or abnormalities. These results are interpreted to mean that eversion of the prepupal head is not necessary for the initiation or the development of the tumor. It is also concluded that the tu-h trait is autonomous, and that the tumors are already determined tissue at the late third instar stage.

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