Synthesis of mitochondrial DNA in spermatocytes of Rhynchosciara hollaenderi

Mary Ann Handel, John Papaconstantinou, David P. Allison, Emilia M. Julku, Eugene T. Chin

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

During the mid to late 4th instar period of larval development, the mitochondria of Rhynchosciara spermatocytes undergo highly characteristic morphological changes. In late meiosis the enlarged mitochondria fuse to form a single mitochondrial element which will ultimately extend the length of the spermatid tail. Our studies have shown that synthesis of a circular DNA occurs during this period of mitochondrial "differentiation." This DNA has a density of 1.681 g/cm3; and its synthesis cannot be detected in somatic tissues such as salivary gland, fat body, or gastric cecum. From analysis of DNA extracted from mitochondrial pellets, we have shown that the circular DNA is associated with the mitochondria. The contour length of the mitochondrial DNA is 9 μm, equivalent to a molecular weight of 18 × 106. Although most metazoan mitochondrial DNAs exhibit contour lengths of approximately 5 μm (10 × 105 daltons), there is no extractable 5 μm circular DNA in these spermatocytes. Therefore, we conclude that either Rhynchosciara spermatocytes possess a distinct 9 μm mitochondrial DNA or that the spermatocyte mitochondrial DNA represents dimers of 5 μm monomers.

Original languageEnglish (US)
Pages (from-to)240-249
Number of pages10
JournalDevelopmental Biology
Volume35
Issue number2
DOIs
StatePublished - Dec 1973
Externally publishedYes

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ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology

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