• Prem Narain

      Articles written in Journal of Genetics

    • Analysis of 6 × 6 diallel cross for EGG production inDrosophila melanogaster

      H. P. Singh S. S. Prabhu Prem Narain Swastika Negi

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      There is a considerable amount of interaction between the environment and the genetic factors controlling egg production InDrosophila melanogaster.

      The genes affecting egg production exhibit both additive genetic effects and dominant deviations. They also show non-allelic interactions. The non-allelic interaction between G and D results in low egg production.

      An asymmetry in the distribution of positive and negative allels exists in the parents, which was understandable as three of the six lines included in the trial were selected for low egg production and the other three for high egg production.

      There are probably present more dominant than recessive genes affecting egg Production in the parental stock used in these studies; the ratio of recessives to dominants being of the order of 1:4. Low egg production is due to recessive genes, high egg production to their dominant allels.

      Dominance deviations present were largely unidirectional.

      The order of dominance of the six lines used was D, B, E, C, A, F.

    • Homozygosity in a selfed population with an arbitrary number of linked loci

      Prem Narain

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      A generalised ‘coefficient of relationship’ between two individualsX andY has been defined with any number of linked loci.

      Recurrence relations for ϕ-, π- and ξ-functions (Schnell, 1961) in the case of two and three loci have been obtained.

      Solutions for recurrence relations have been given for ϕ-function upto the case of any number of linked loci.

      It has been found that the effect of linkage on the homozygosity of a selfed population is more with a greater number of linked loci and is maximum after one generation of selling. With three linked loci, the pairs of values ofp12, p23when taken as (.1, .1) exert a greater effect than (.3, 0) or (.5, 0) but this is true only upto two generations of selfing.

      With more than one locus, the rate of inbreeding is not constant with further generations of selfing. It depends on the number of generations of selling and the recombination values.

    • Analysis of a 6 × 6 diallel cross for hatchability inDrosophila melanogaster

      S. S. Prabhu Prem Narain H. P. Singh Swastika Rawat

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    • Efficiency of selective breeding based on a phenotypic index

      Prem Narain A. K. Mishra

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      This article discusses the efficiency of selective breeding based on ‘phenotypic index’ which is defined as the deviation of the phenotypic value of the trait from its expected value predicted with the help of one or more auxiliary traits. The conditions under which the efficiency of such a procedure is greater than one have been theoretically studied. The practical relevance of this technique has also been demonstrated by applying it to breeding data on cattle.

    • The conditional Markov chain in a genetic context

      Prem Narain

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      A theory of the stochastic change in the frequency of a gene in finite populations conditional to its eventual fixation has been developed employing a Condiditional Markov Chain. The probability generating function of the distribution of time until fixation of a particular allele as well as the eigen-roots and eigenvectors of the conditional process with binomial transition probabilities have been studied. The theory has been applied to investigate the effect of linkage on the mean and standard deviation of time until fixation of a gamete in populations practising self-fertilization. It has been found that linkage decreases or increases the average and standard deviation of time to fixation of a coupled gamete according as the initial population consists of a coupling or repulsion heterozygote respectively.

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