Distribution of heterochromatin on the mitotic chromosomes of Musca domestica L. in relation to the activity of male-determining factors |
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Authors: | Monika Hediger Markus Niessen Jutta Müller-Navia Rolf Nöthiger Andreas Dübendorfer |
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Institution: | (1) Institute of Zoology, University of Zürich-Irchel, CH-8057 Zürich, Switzerland, CH;(2) Institute of Anthropology, University of Mainz, D-55099 Mainz, Germany, DE |
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Abstract: | In the housefly, male sex is determined by a dominant factor, M, located either on the Y, on the X, or on any of the five autosomes. M factors on autosome I and on fragments of the Y chromosome show incomplete expressivity, whereas M factors on the other autosomes are fully expressive. To test whether these differences might be caused by heterochromatin-dependent
position effects, we studied the distribution of heterochromatin on the mitotic chromosomes by C-banding and by fluorescence
in situ hybridization of DNA fragments amplified from microdissected mitotic chromosomes. Our results show a correlation between
the chromosomal position of M and the strength of its male-determining activity: weakly masculinizing M factors are exclusively located on chromosomes with extensive heterochromatic regions, i.e., on autosome I and on the Y chromosome.
The Y is known to contain at least two copies of the M factor, which ensures a strong masculinizing effect despite the heterochromatic environment. The heterochromatic regions
of the sex chromosomes consist of repetitive sequences that are unique to the X and the Y, whereas their euchromatic parts
contain sequences that are ubiquitously found in the euchromatin of all chromosomes of the complement.
Received: 20 February 1998; in revised form: 11 May 1998 / Accepted: 23 May 1998 |
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