Showing papers in "Journal of Genetics in 1974"

A scaling which removes bias of Abeywardena’s estimator of repeatability

Abstract: Abeywardena’s (J,Genetics, 61, 27–51, 1972) estimator of repeatability was shown to be biased, using both the theoretical model for the dependence structure of a repeatability data set and analyses of his simulated data. A scaling involving the number of observations per individual corrected the bias.

Autosomal recombination in males ofDrosophila melanogaster caused by a transmissible factor

Abstract: The phenomenon of male recombination has been found in more than twenty per cent of lines derived from wild-caughtDrosophila melanogaster. The recombination appears to be caused by a factor which is attached to, and transmitted with chromosomes, but which is readily transposed to other chromosomes. The possibility exists, however, that the factor is also capable of independent existence in the nucleoplasm. Extensive testing indicates that the factor is not contagious. The factor has been named “Male Recombinant Factor” or “MRF”.

Geographic and taxonomic distribution of anthocyanin genes in New World cottons

Abstract: Patterns of anthocyanin development in the vegetative and floral parts of New World cotton species are determined by the actions and interactions of two genetic loci with a minimum of three alleles in each:R 1,R 1 D ,r 1, andR 2 v ,R 2,r 2. The most frequent genotypic combinations are:r 1 r 1 R 2,R 2 andr 1 r 1 r 2 r 2. A survey of the geographical and taxonomic distribution of anthocyanin genes in living collections from Latin America provides the following information:R 1 is a rare mutant, restricted in nature to one race ofhirsutum (Gossypium hirsutum racelatifolium Hutchinson) and is localized in southwest Mexico.R 2 v , on the contrary is widely distributed in Latin America, through the Caribbean region of South America, the Guianas and the West Indies. It has not been found in Central America. The gene is shared by two species which are sympatric over a major part of their ranges—G. barbadense L. (including var.brasiliense)and G. hirsutum racemarie-galante Hutchinson.R 2 (Petal Spot) is common toG. barbadense andG. hirsutum, its frequency varies in the different races of the latter species.

On the genetics of psoriasis

Abstract: To elucidate the mode of inheritance in psoriasis, Falconer's model for estimating heritability which is under the assumption of multifactorial inheritance, was applied to the data of Hellgren (1967) from Sweden. The heritability estimates were based on both manifest and potential psoriasis since a clear separation of these two categories was impossible. These estimates were 64% for parents, 60% for siblings and 52% for all first degree relatives which included the children of psoriatic cases. For second degree relatives it was 48%. None of these differences are statistically significant. The results are discussed.

Patterns of heterosis and crossing barriers resulting from increasing genetic distance between populations of theMimulus luteus complex

Abstract: Ability of several populations of theMimulus luteas complex to intercross was compared with an estimate of genetic divergence of the populations derived from a Prim network based on 134 traits. On the average we find that low levels of genetic differentiation result in heterosis or partial interference with ability to intercross and that with increasing genetic divergence, these are replaced with increasingly strong barriers to gene exchange.

The use of selfing in selection of forest trees

Abstract: The biological and theoretical advantages and disadvantages of using progeny of self-pollinated trees in a selection program based on general combining ability are discussed. A replicated pilot experiment usingMimulus guttatus compared the realized gains from mass selection to realized gains using a selfed-family selection scheme. This scheme included a within-family selection step, or culling, to offset the effects of inbreeding depression, prior to selection between culled families.

Selection on the fertility of translocation heterozygotes inDrosophila melanogaster. 1. The extent of the changes produced by selection

Abstract: As part of a study on the suitability of translocations for insect pest control, artificial selection was applied for either higher or lower egg hatchability in each of the reciprocal matings between a translocation heterozygote and a translocation homozygote. In each of four selection lines, there was response to selection but, after 3–4 generations, limits were reached beyond which further selection gave no response. On reversing the directions of selection, the high and low lines rapidly exchanged their levels of egg hatchability and then established new plateaux. Relaxation of selection caused convergence towards the original unselected level. It is concluded that individuals with extremely high or low fertility were disfavoured by natural selection. Populations initiated from two different translocation homozygotes formed a stable polymorphism and after propagation in bottles for 10 generations, small increases were found in the fertility of the double translocation heterozygotes compared with the same genotype newly produced from unselected homozygote stocks. It is concluded that, under the conditions of the bottle cultures, natural selection favoured increase in fertility of the double heterozygotes.

Genetic effects of age on performance in random-bred mice

Abstract: Two lines of mice (A and Y) differing in age at mating were maintained with as similar ancestry as possible for nine and 13 generations, and were used for diallel matings to contemporaneously produce various genotypes of offspring (A, Y, F1, F2, and backcross). Body weights of offspring at birth, and at 12, 20 and 42 days of age were recorded, and data on actual and logarithmic scales were analysed Regression of the mean body weight for the respective genotype on the coded A-line gene effects was significant (P < 0. 05) only in 20-day weight on both actual and logarithmic scales. When the mean body weight was expressed in standard deviation unit, regression was significant (P < 0. 05) for 20-day and 42-day weight on actual scale. It was concluded that birth weight and 12-day weight were not genetically affected by accumulated parent age effects. The results inconclusive with respect to 20-day and 42-day weight were discussed.

Hot Aceto-Orcein for staining human chromosomes

Abstract: A i r d r i e d s l i d e s a r e d i p p e d in a b s o l u t e a l c o h o l f o r a m i n u t e and d r i e d a t 5 5 6 0 ~ on a s l i d e w a r m e r . 0. 5% O r c e i n * (0. 5 g r a m o r c e i n in 100ml of 605/0 acetic acid) is slowly heated to about 80~ and filtered hot. Dried slides which are kept at 55-60~ until staining are dipped into the hot orcein stain for a minute or two, It is important that the stain be hot and the slides be kept warm prior to staining. This could be done by keeping the stain in a water bath between 80 ~176 and the slides on a slide warmer between 55 ~176 After staining, the excess stain on the slide is dripped off completely by holding the slide at an angle, Observe the slid~ under the microscope and if overstained a dip in 95~a alcohol should help remove excess stain. If staining is inadequate, keep the slide for 5 to i0 additional minutes in the hot stain. When once the slide is satisfactorily stained, it is dipped in absolute alcohol for a minute, taken through xylol and mounted in canada balsam or any other mounting medium.

A study of inbreeding in some models of artificial selection

Abstract: An attempt is made to study the progress of inbreeding in a population by simple models of artificial selection. One or two top ranking individuals are selected based on the phenotypic value of a metric from theN progenies resulting from any particular mating (denoted as Model 1 and Model 2). The generation matrix method is employed to study the progress towards homozygosity. The probability that a selected individual is of a given genotype or that a selected pair consists of specified genotypes has been computed by numerical integration as well as by simulation, assuming the phenotypic distribution to be normal with the mean at the genotypic value and a given variance. It is observed that Model 1 promotes homozygosity more quickly than Model 2 as expected. Modifications due to dominance in the progress towards homozygosity are also discussed. The study throws some light on simulation studies in genetics.

Studies of the aberrant eumenine wasp,Xenorhynchium nitidulum (Fabr.)

Abstract: The females of theXenorhynchium nitidulum can provide for their larvae either by mass provisioning or by progressive provisioning. They can also reuse cells that they have built themselves. At least during progressive provisioning and cell reusing behaviour, the wasps journies to collect mud for wall building, to collect plant gum for daubing and to collect holometabolous insect larvae to provision the cell, are much less grouped than is usual in the solitary wasps; the egg is not laid at one characteristic stage in the building of a cell; prey may or may not be present when an egg hatches; and may or may not be present when a cell is sealed. After metamorphosis the imagines have taken several hours to complete the gnawing away of the lid of their cell, before emerging and flying.

Reduction of radiation damage by mechanical vibration inDrosophila melanogaster

Abstract: Mechanical vibration (100 Hz) following irradiation (4000r) exerts a repairing effect on radiation induced damage. Productivity and sex-ratio differences inDrosophila melanogaster were less severely affected in a group, the male parents of which had been both inadiated and vibrated than in a positive control group, the male parents of which were subjected to irradiation only. Repair of radiation induced damage may have been facilitated by vibration by increasing oxygen utilization and/or metabolism. Previous work suggests that vibration induced mutations were repaired to an extent greater than expected. Synthesis of enzymes of importance during repair, stimulated (induced)via a general stress response as a result of radiation damage, may permit immediate initiation of repair of vibration induced damage.

On Haldane’s exact test for random mating

Abstract: Consider a k-allelic system at an atttosomal locus with alleles A~, A . , , . . . , A~ and with gene frequencies p~, pz, . . . , lh~ respectively. In a random sampl~ of size N, let thj stand for thG observed frcqt, cncy of tl'~c gcnotype A,Aj (iS_-j). We define as many D's as the number of hetcrozygotcs by D, j=4n , ,n j j -n , (n , j 1) : i < . j = 1,2, . . . , k whose expectations art given by E (Do) = N (N -I) (4g~gjj -go ~') which vanish under random mating, where g,~ is the expected proport ion of the genotype A~Aj. In this general setup, Haldane's case corresponds to k = 2. To develop the methodology, we shall discuss Haldane's two-allele problem in the. next section and then generalize the results to multiple alleles in the last sect ion.