To find out the incidence of sex-linked defective color vision in people of Bathinda district in southern Punjab, a survey was planned among the school going boys using standard Ishihara’s Color Plates Chart. The present study was conducted on a total of 1,002 individuals belonging to 9 caste,11 backward caste and 5 scheduled caste endogamous groups, as well as a few from Muslim and Christian religious groups. In the total individuals screened as many as 34 cases of red-green color blindness and 3 of total color blindness were detected. All the red-green color blind subjects were found to be of deutan type, comprising 8 strong and 26 mild cases. No protan individual was detected in the present survey. Of the 27 endogamous groups tested, 16 groups showed absence of the trait while the incidence in remaining groups of the castes, backward castes and schedule castes were in rather similar and broad ranges between 0 to 6.7%, 0 to 6.3% and 0 to 4.7% respectively. Besides, in each of these 3 caste groupings, 1 total color blind subject was found. Compared to some initial studies on color blindness available from Punjab(average 5.2%),the present and some other recent surveys provide comparatively lower estimates of all trait (average 3.22%) which is found to be very close to that of U.P.(3.28%) and Delhi (3.15%) suggesting similarities in this genetic trait among populations of these states of the region. While in 249 populations on the North-Western Indian region so far tested the average incidence of color blindness was calculated to be 3.98%.To fully appreciate the true variation of this genetic trait and also to complete the genetic map of people of people of Punjab, further studies, are required.

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Incidence Of Color Blindness Among Some Endogamous Groups Of Bathinda District, Punjab

Sample data from a number of sub-populations are often investigated in order to integrate the findings of different research studies on a particular area. In case of compositional samples, like the allele frequencies collected at a single locus in different surveys, the data are independent multinomial vectors. Each multinomial distribution depends on a specific probability vector, that is, the unknown relative composition of the sub-population. A Bayesian hierarchy approach is proposed here to model the variability of the sub-composition vectors around a common mean with possibly different scales. The common mean can be seen as the relative composition of the aggregated population. Scale parameters are well known in Biology as the Wright's inbreeding coefficients. The method presented here extends some previous work by assuming less prior knowledge on the subject and constraints on the model. A relatively simple Monte Carlo algorithm is described to perform joint inferences on general and local compositions and inbreeding coefficients. The method is applied on two case studies. The first one is based on DNA samples from ten Italian regions at the loci TH01 and FES, obtained from a database currently used for forensic identification, in which inbreeding assessments can be crucial. The second application is based on a set of colour-blind sample rates in North-East Indian populations collected by Choudhury (1994). The Author found some controversial results from the classical test for comparing proportions. A clearer picture, instead, is obtained by the current Bayesian approach.

Bayesian multilevel modelling of compositional data for simultaneous inferences on Allele compositions and inbreeding coefficients

To understand nature and causes of variation in natural populations, independent samples often review and integrate the findings of several research studies. In this case, we may expect some differences, but also some persistent patterns in the observed frequencies.

An Adaptive SIR Algorithm for Bayesian Multilevel Inference on Categorical Data

Variation in colour-blindness in some of the populations of North-East India has been examined. The people of North-East India are found to be extremely variable with regard to this trait, the frequency ranging from 0 to 8.05%. An attempt has also been made to examine the present findings in light of the hypothesis put forward by Post (1962a,b) and others about selection relaxation.

B. Choudhury

Papers

Variation in colour-blindness in North-East India