Drosophila male is an example of achiasmatic meiosis which lacks crossingover and chiasmata during meiosis. Previous studies showed that homologous pairing of both euchromatin and centromeres is lost during middle prophase I, however, homologs are still connected as they form bivalents. The X-Y pair utilizes a specific repeated sequence within the heterochromatic ribosomal DNA blocks as a pairing site. No pairing sites have yet been identified for the autosomes. To search for such sites, we utilized probes specifically targeting heterochromatin regions to assay pairing sequences and behavior in meiosis by fluorescence in situ hybridization (FISH). We found that the fourth homologs pair at the heterochromatic region 61 and associate with the X chromosome throughout prophase I. The pairing of the fourth homologs is disrupted in the homolog conjunction complex mutants. Conversely, six tested heterochromatic regions of the major autosomes (second and third chromosomes) have proved to be largely unpaired after early prophase I. This suggests that pairing mechanism of the major autosomes may differ from the sex and fourth chromosomes; stable connections between major autosomal homologs might occur at different sites along chromosomes in different cells by analogy to chiasmata. Moreover, FISH analysis also revealed two distinct patterns of sister chromatid cohesion in heterochromatin: regions with stable cohesion and regions lacking cohesion, suggesting that sister chromatid cohesion is incomplete within heterochromatin but with preferential sites in male meiosis.Modifier of Mdg4 in Meiosis (MNM) and Stromalin in Meiosis (SNM) are components of homolog conjunction complex and essential for homolog pairing and segregation in male meiosis. Using yeast two-hybrid assay and co-immunoprecipitation, we showed that the MNM and SNM interact with each other. Specifically, the BTB domain of MNM is responsible for the interaction with SNM, whereas FLYWCH domain of MNM is crucial for this interaction but does not directly interact with SNM. Additionally, point mutation analysis revealed that L9K replacement of the BTB domain weakened the MNM-SNM interaction and caused high frequencies of chromosome nondisjunction. In conclusion, these results provide a biochemical basis for the mechanism of homolog pairing and support the role of homolog conjunction complex in male meiosis.

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In this research we attempted several modifications to microstrip ring/loop antennas to design multi-frequency antennas through systematic approaches. Such multi-frequency antennas can be useful while building compact terminals to operate at multiple wireless standards. One of the primary contributions was the use of a capacitive feed arrangement that enables simultaneous excitation of multiple concentric rings from an underlying transmission line. The combined antenna operates in the same resonant bands as the individual rings and avoids some of the bands at harmonic frequencies. A similar feeding arrangement is used to obtain dual band characteristics from just one ring, with improved bandwidth. This is made possible by widening two adjacent sides of a square ring antenna symmetrically, and attaching an open stub to the inner edge of the side opposite to the feed line. Use of fractal segments replacing the side with the stub also results in a similar performance. Use of fractal geometries has been widely associated with multi-functional antennas. It has been observed from the parametric studies that, the ratio of the resonant frequencies can range from 1.5 to 2.0. This shows some flexibility in systematically designing dual-band antennas with a desired pair of resonant frequencies. An analysis technique based on multi-port network modeling (MNM) has been proposed to accurately predict the input characteristics of these antennas. This approach can make use of the ordered nature of fractal geometries to simplify computations. Several prototype antennas have been fabricated and tested successfully to validate simulation and analytical results.