Genome Size and Determination of DNA Content of the X Chromosomes, Autosomes, and Germ Line-Limited Chromosomes of Sciara Coprophila
Document Type
Article
Publication Date
11-1-2006
Description
The unique chromosome biology of the fungus fly Sciara coprophila has fascinated investigators for over 80 years. Male meiosis exhibits a monopolar spindle, nonrandom segregation of imprinted chromosomes and nondisjunction of the X chromosome. The unusual mechanism of sex determination requires selective elimination of X chromosomes in embryogenesis. Super-numerary (L) chromosomes are also eliminated from the soma during early cleavage divisions. Distinctive DNA puffs on the larval salivary gland chromosomes are sites of DNA amplification. As a foundation for future genome studies to explore these many unusual phenomena, we have used DNA-Feulgen cytophotometry to determine genome size from hemocyte nuclei of male (X0) and female (XX) larvae and adults. The DNA content of the X chromosome is ∼0.05 pg DNA and the autosomal complement is ∼0.45 pg DNA. Measurements of DNA levels for individual sperm from adults showed that the DNA contribution of the germ line-limited (L) chromosomes constitutes as much as 35% of the DNA of the male gamete. A parallel study using Sciara ocellaris, a related species lacking L chromosomes, confirmed the presence of two X chromosomes in the sperm of this species.
Citation Information
Rasch, Ellen. 2006. Genome Size and Determination of DNA Content of the X Chromosomes, Autosomes, and Germ Line-Limited Chromosomes of Sciara Coprophila. Journal of Morphology. Vol.267(11). 1316-1325. https://doi.org/10.1002/jmor.10478 PMID: 17051543 ISSN: 0362-2525