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Biomedical subjects

M Madhu

Publications and source records attributed to M Madhu.

5 recordsLinked to original sources
PubMed2005

SilkSatDb: a microsatellite database of the silkworm, Bombyx mori.

The SilkSatDb (silkmoth microsatellite database) (http://www.cdfd.org.in/silksatdb) is a relational database of microsatellites extracted from the available expressed sequence tags and whole genome shotgun sequences of the silkmoth, Bombyx mori. The database has been rendered with a simple and robust web-based search facility, developed using PHP. The SilkSatDb also stores information on primers developed and validated in the laboratory. Users can retrieve information on the microsatellite and the protocols used, along with informative figures and polymorphism status of those microsatellites. In addition, the interface is coupled with Autoprimer, a primer-designing program, using which users can design primers for the loci of interest.

Animals↗
PubMed2005

Genetic mapping of Z chromosome and identification of W chromosome-specific markers in the silkworm, Bombyx mori.

In the silkworm, Bombyx mori, the female is the heterogametic (ZW) sex and the male is homogametic (ZZ). The female heterogamety is a typical situation in the insect order Lepidoptera. Although the W chromosome in silkworm is strongly female determining, no W-linked gene for a morphological character has been found on it. The Z chromosome carries important traits of economic value as well as genes for various phenotypic traits, but only 2% of molecular information based on its relative size is known. Studies conducted so far indicate that the Z-linked genes are not dosage compensated. In the present study, we constructed a genetic map of randomly amplified polymorphic DNA fragments (RAPD), simple sequence repeats (SSR), and fluorescent intersimple sequence repeat PCR (FISSR) markers for the Z chromosome using a backcross mapping population. A total of 16 Z-linked markers were identified, characterized, and mapped using od, a recessive trait for translucent skin as an anchor marker yielding a total recombination map of 334.5 cM. The linkage distances obtained suggested that the markers were distributed throughout the Z chromosome. Four RAPD and four SSR markers that were linked to W chromosome were also identified. The proposed mapping approach should be useful to identify and map sex-linked traits in the silkworm. The economic and evolutionary significance of Z- and W-linked genes in silkworm, in particular, and lepidopterans, in general, is discussed.

Animals↗
PubMed2004

Survey and analysis of microsatellites in the silkworm, Bombyx mori: frequency, distribution, mutations, marker potential and their conservation in heterologous species.

We studied microsatellite frequency and distribution in 21.76-Mb random genomic sequences, 0.67-Mb BAC sequences from the Z chromosome, and 6.3-Mb EST sequences of Bombyx mori. We mined microsatellites of >/=15 bases of mononucleotide repeats and >/=5 repeat units of other classes of repeats. We estimated that microsatellites account for 0.31% of the genome of B. mori. Microsatellite tracts of A, AT, and ATT were the most abundant whereas their number drastically decreased as the length of the repeat motif increased. In general, tri- and hexanucleotide repeats were overrepresented in the transcribed sequences except TAA, GTA, and TGA, which were in excess in genomic sequences. The Z chromosome sequences contained shorter repeat types than the rest of the chromosomes in addition to a higher abundance of AT-rich repeats. Our results showed that base composition of the flanking sequence has an influence on the origin and evolution of microsatellites. Transitions/transversions were high in microsatellites of ESTs, whereas the genomic sequence had an equal number of substitutions and indels. The average heterozygosity value for 23 polymorphic microsatellite loci surveyed in 13 diverse silkmoth strains having 2-14 alleles was 0.54. Only 36 (18.2%) of 198 microsatellite loci were polymorphic between the two divergent silkworm populations and 10 (5%) loci revealed null alleles. The microsatellite map generated using these polymorphic markers resulted in 8 linkage groups. B. mori microsatellite loci were the most conserved in its immediate ancestor, B. mandarina, followed by the wild saturniid silkmoth, Antheraea assama.

Animals↗
PubMed1994

Mucin coding sequences are remarkably conserved.

Mucins are complex glycoproteins expressed by glandular epithelia and the carcinoma which develop from these tissues. The core protein is aberrantly glycosylated in cancers, and some antibodies show specificity in their reactions with the cancer-associated mucins, which also contains epitopes recognized by T-cells from pancreatic and breast cancer patients. Based on the PCR amplification of the mucin coding sequences, hybridization analysis and determination of the sequence divergence we present the evidence that mucin coding sequences are conserved in a number of species. A broad series of organisms were examined for analogous sequences. Data show that mucin-type sequences are present in a variety of mammals, but less apparent in chicken and yeast. Divergence increased in the order human, monkey, rabbit/rat/cow, mouse; chicken and yeast exhibited minimal homology. Furthermore, nucleotide sequences not included in the tandem repeats, a common feature of mucin core structure, are more conserved than the flanking sequences which also suggests that the flanking sequences may be functionally significant while repeats are structurally important. The hybridization bands showed different restriction patterns (suggesting for the existence of the restriction fragment length polymorphism). Northern analysis indicates message polydispersity, commonly seen with this class of RNA. The major features of the protein appear broadly conserved in the different mammalian species examined. The evolutionary significance of the above studies has been discussed.

Animals↗