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The Molecular Structure of the Beadex and Heldup-A Loci of Drosophila melanogaster


Mattox, William Wayne (1987) The Molecular Structure of the Beadex and Heldup-A Loci of Drosophila melanogaster. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/c2k4-a231.


Genetic studies indicate that excess-of-function Beadex mutations and loss-of-function heldup-a mutations affect different parts of a single bipartite genetic unit. In order to investigate the molecular nature of the Beadex and heldup-a mutations we isolated DNA from a 49 kilobase region surrounding the sites at which these mutations occur. We found gross structural alterations associated with one heldup-a mutation and each of the 13 different Beadex mutations that we examined. As expected from previous genetic studies these loci are separated by only a short molecular distance which is at most 1.5 kilobases. The structural alterations associated with the thirteen Beadex excess-of-function mutations examined are clustered within a three kilobase region. Several of these mutations are found to be associated with the deletion of part of an 800 bp region. This indicates that an element that normally represses gene activity is located within this region: A 200 base pair segment which is required for the function of the wild-type heldup-a locus is defined using a heldup-a mutation which results from a small deletion.

Two RNA transcripts have been found which span this 200 base pair segment. One of these two transcripts, a four kilobase RNA, is expressed during stages in which the Beadex structural gene product is expected to be active. The structure of this transcript is affected by one heldup-a mutation and each of five Beadex mutations that were examined. However, only one of the Beadex mutant alleles expresses significantly elevated levels of this RNA. Other RNA species in the region surrounding the the Beadex and heldup-a loci were not affected either in amount or size by Beadex mutations.

We have also reintroduced a wild-type 10.4 kilobase fragment, which includes the region m which Beadex and heldup-a mutations map, into the Drosophila genome by P element mediated transformation. This introduced fragment fails both to complement loss-of-function heldup-a mutations and to enhance an excess-of-function phenotype. This result indicates that some sequences required for the normal heldup-a function must be located outside this 10.4 kilobase region.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Biology
Degree Grantor:California Institute of Technology
Major Option:Biology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Lewis, Edward B. (advisor)
  • Davidson, Norman R. (co-advisor)
Thesis Committee:
  • Lewis, Edward B. (chair)
  • Wold, Barbara J.
  • Meyerowitz, Elliot M.
  • Simon, Melvin I.
  • Davidson, Norman R.
Defense Date:14 July 1986
Additional Information:Thesis title listed in 1987 commencement program varies from actual thesis: The Molecular Structure of the Beadex and Heldup-A Loci of Drosphila melanogaster.
Funding AgencyGrant Number
Jean Weigle Memorial FundUNSPECIFIED
Record Number:CaltechTHESIS:10212019-143142376
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 1. adapted for Appendix 2.
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11834
Deposited By: Mel Ray
Deposited On:21 Oct 2019 21:51
Last Modified:16 Apr 2021 22:16

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