Prevalence of congenital heart diseases in Mysore.

Background: Prevalence studies on Congenital heart Diseases (CHDs) have been done several times world wide and such studies are very limited in Indian populations. A few earlier studies in India have reported an increased prevalence of CHDs ranging from 2.25 to 50.89 per 1000 live births. Aims and Objective: To study the prevalence of congenital heart diseases in Indian population. Materials and Methods: Data on the prevalence of CHDs were collected and analyzed from the three major hospitals of Mysore, Cheluvamba Hospital, CSI Holdsworth Memorial Hospital and J.S.S Hospital from the year 2000 to 2004. Results: The prevalence of CHDs for five years in Mysore hospitals ranges from 6.6 to 13.06 per 1000 live births. The most frequent type of CHD was found to be VSD (40.47%) followed by ASD (19.06%), TOF (13.38%) and PDA (9.53%). It is clear that the maximum CHDs were detected in the first year of life when compared to the later years of life. The prevalence of CHDs in Mysore is increasing from 2000 to 2004 which might be due to the improvement of diagnosis, attention or awareness among the medical authorities on the disease. Conclusion: The prevalence of CHDs in Mysore is not very high as reported in other parts of the country, however; it is an important disease which needs an immediate medical attention.

Modes of genetic transmission of dyslexia in south Indian families.

Background: Dyslexia is a major educational problem, but the studies on genetics of dyslexia are very limited in India. There is a great dearth of proper statistical data to show the incidence of dyslexia in Indian population. More over inheritance pattern of dyslexia is not well established in our population. Aims & Objective: To establish the inheritance pattern of dyslexia in 23 selected families. Materials and Methods: We have ascertained 23 dyslexic probands and their families from the state of Karnataka. Individuals with above 8 years of age, normal performance intelligence quotient (>85) and remarkable deviation in reading and writing skills compared to chronological age were considered for the study. Based on the genetic registry pedigrees of the families were constructed. Results: Based on the affectedness, the dyslexia phenotypes were classified into four types: severe reading spelling deficit, mild reading spelling deficit, severe spelling deficit and mild spelling deficit. Severe dyslexia phenotypes were more frequent than mild phenotypes. Mild spelling deficits were better compensated than the other types. It was found that autosomal dominant inheritance pattern of dyslexia was more prevalent than autosomal recessive and sporadic pattern in the present study. Conclusion: Family history of dyslexia is a consistent risk factor; therefore this knowledge can be applied to the prevention and remediation of dyslexia.

Incipient sexual isolation in the nasuta-albomicans complex of Drosophila: mating preference in male-, female- and multiple-choice mating experiments.

Interracial divergence is an important facet of speciation. The nasuta-albomicans complex of Drosophila with sixteen morphologically identical, karyotypically different but cross-fertile races is an excellent system to study a few dimensions of raciation. Drosophila nasuta nasuta, Drosophila nasuta albomicans, Cytorace 1, Cytorace 2, Cytorace 3 and Cytorace 4 of this subgroup have been subjected to male-, female- and multiple-choice mating experiments. Out of 8456 crosses conducted, 7185 had successful matings. The overall impression is that mating is far from random amongst these six closely related races of the nasuta-albomicans complex. The males of D. n. albomicans, Cytorace 1 and Cytorace 4 in male-choice, the females of Cytorace 1 and Cytorace 2 in female-choice, and the males and females of D. n. nasuta, D. n. albomicans, Cytorace 1 and Cytorace 4 against the males and females of Cytorace 2 in multiple-choice experiments, had significantly more homogamic matings than expected. Thus in this study of evolutionary experimentation on raciation under laboratory conditions, we have documented the initiation of preference for conspecific matings among closely related and independently evolving members of the nasuta-albomicans complex of Drosophila.

Incipient sexual isolation in the nasuta-albomicans complex of Drosophila: no-choice experiments.

Drosophila nasuta nasuta and Drosophila nasuta albomicans are cross-fertile races of Drosophila. Hybridization between these races in the laboratory has given rise to new races (Cytoraces), among which karyotypic composition differs from one another and also from those of the parental races. In this study, we search for the evidence of incipient reproductive isolation among the parental races and four Cytoraces by assessing the fraction of no-matings, mating latency and copulation duration in all possible types of homo- and heterogamic crosses (N = 4184). In no-choice conditions, the latency time (time to initiation of copulation) is lower in homogamic crosses than in heterogamic crosses for both parental races and Cytoraces. Latency time and copulation duration are negatively correlated, whereas fraction of no matings is positively correlated with latency time. Thus these six closely related races of the nasuta-albomicans complex show the initiation of the earliest stages of pre-zygotic isolation, manifested as a tendency for matings to be initiated earlier and more often, and for a longer duration, among homogamic rather than heterogamic individuals

Racial divergence in abdominal bristles among parental races and newly evolved cytoraces of nasuta-albomicans complex of Drosophila.

Cytoraces are the products of interracial hybridization between Drosophila nasuta nasuta and D. nasuta albomicans. These races differ from their parents in the chromosome composition, mating preference, certain fitness phenotypes and also a few morphophenotypic traits. Now, these cytoraces are passing through 330 generations. Racial divergence in the 4th and 5th abdominal bristles among the parental races and the newly evolved cytorace 1 and 2 is reported. The results revealed that the parental races have more number of bristles than newly evolved cytoraces. Thus, these cytoraces are evolved/evolving with reduced abdominal bristle number and better fitness.

Patterns of replication in the neo-sex chromosomes of Drosophila nasuta albomicans.

Drosophila nasuta albomicans (with 2n = 6), contains a pair of metacentric neo-sex chromosomes. Phylogenetically these are products of centric fusion between ancestral sex (X, Y) chromosomes and an autosome (chromosome 3). The polytene chromosome complement of males with a neo-X- and neo-Y-chromosomes has revealed asynchrony in replication between the two arms of the neo-sex chromosomes. The arm which represents the ancestral X-chromosome is faster replicating than the arm which represents ancestral autosome. The latter arm of the neo-sex chromosome is synchronous with other autosomes of the complement. We conclude that one arm of the neo-X/Y is still mimicking the features of an autosome while the other arm has the features of a classical X/Y-chromosome. This X-autosome translocation differs from the other evolutionary X-autosome translocations known in certain species of Drosophila.

Pattern of sexual isolation between parental races (Drosophila nasuta nasuta and D.n. albomicans) and the newly evolved races (Cytorace I and II).

D.n. nasuta, D.n. albomicans, Cytorace I and Cytorace II [Chromosoma, 93 (1986) 243] are closely related strains of the nasuta subgroup. Through male choice and female choice experiments, the pattern of sexual isolation if any, among them was analysed. Differential mating preference of males and females of these races suggests that they are passing through the process of anagenesis. Therefore, this, as an evolutionary experiment under laboratory conditions, offers a rare opportunity to witness different pattern and levels of divergence among four cytogentically parsimonious races of Drosophila.