Showing papers in "Journal of Genetics in 1966"

Mutagenic activity in Drosophila of two pyrrolizidine alkaloids

Abstract: The data on mutagenicity are shown in Table 1. Both fulvine and retrorsine show moderate activity, falling into Clark’s (1960) second category. Isatidine, the N-oxide of retrorsine is much less active than the base itself, a result which is consistent with those of Clark. Monocrotaline and fulvine induce translocations, but at a rate which is very low compared with the incidence of sex-linked recessive lethals (cf. Avanzi, 1961; Clark, 1963).

Heterostyly inOldenlandia scopulorum bull.

Abstract: Heterodistyly inOldenlandia scopulorum Bull., a member of the Rubiaceae, is described. The species is characterised by two floral forms, the pin with long style and short anthers and thrum with short style and long anthers. Further the pin has small pollen grains and long stigmatic papillae while the thrum has large pollen grains and short stingmatic papillae. Pollination experiments with pin and thrum forms in compatible and incompatible crosses are reported. Pin self is compatible while thrum self incompatible. The cross pin x thrum is more fertile than thrum x pin.

Homostyly in heterostyledBiophytum sensitivum DC

Abstract: Heterostyly in Bi@hylum sensitivum DC., (Oxalidaceae) was described by one of the authors in a previous paper (Mayura Devi, 1964). The present commu,~ication is devoted to ~.he morphology and self-compatibility of the homostyled form of this species. The occurrence of homostyly in an otherwise heterostyled species is so far k:aown in 13 genera comprising 23 species (Bit Bahadur, 1964). Homostyly in hetero-tristyled species is known ontv in Lythrum salicaria L., a member of the Lythraceae (Stout, 1925). In these homostyled forms described by Stout, the height of the style corresponds to one of the two levels of the anthers. These were named semi-homostyles by Stout and they were found to be self-fertile. Recently, Esser (1953) obtained a sell'-fertile homostyle in heterostyled Lythrum salicaria after colchicine treatment.

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

Abstract: 1. A generalised ‘coefficient of relationship’ between two individualsX andY has been defined with any number of linked loci. 2. Recurrence relations for ϕ-, π- and ξ-functions (Schnell, 1961) in the case of two and three loci have been obtained. 3. Solutions for recurrence relations have been given for ϕ-function upto the case of any number of linked loci. 4. 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 ofp 12 , p 23 when taken as (.1, .1) exert a greater effect than (.3, 0) or (.5, 0) but this is true only upto two generations of selfing. 5. 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.

Floral structure and stamens inBombax ceiba L.

Abstract: From the aestivation ofBombax ceiba, two kinds ol'flowers (left-handed and right-handed) are distinguishable, and in a plant Llle two types O c c u r i l l almost the same proportion. The mean number of stamens per flower ranges fi'om 62.72 to 102-00, and this variation is mostly clue to the variation in the number of stamens of the five peripheral staminal bundles of a flower. The central bundle has almost invariably 5 long stamens and | 0 slightly shorter ones, and variation in their number is the least. There is no significant difference in the number of stamens between a left-handed and a right-handed flower and their fi'uits weigh almost the same. Also the mtmbers of their seeds do not differ statistically significantly.

The temperature sensitive (TS) mutations of the bacteriophage T4 B

Abstract: 1 Conditionally lethal temperature sensitive mutants of T4 B bacteriophage have been isolated 2 The mutants obtained fell into 50 complementation groups 3 In most of the isolated mutants, intracellular developmental stages were involved 4 Differences were demonstrated in the kinetics of inactivation when one-step growth study was carried out at higher temperatures On the basis of these differences the mutants were divided into 4 phenotypic groups

Intra-and inter-specific competition in two sibling species of Drosophila,D. melanogaster andD. simulans. II. Inheritance of body-size and correlated responses in fecundity and fertility ofD. simulans

Abstract: With the intention of subsequently doing intraand inter-species competition studies with the laboratory populations of two sibling species of Drosophila viz., D. melanogasger and D. simu{alzs, a programme of selection for body-size, represented by the length of the thorax, was started in 1962 in the laboratory of Professor R. S. Miller at Saskatoon, Canada. A'full report of the metI~ods of stt~dy of progress with the selection for large and small body-sizes fo r / ) , meIanogaslcr and of the analysis of data collected has been presented by Misra (1965). This paper reports results obtained for the population of D. si~mda~zs with selection for large and small body-sizes, forming our high ai~d low lines, carried for 26 generations. Lines are still continuing in the laboratory. Selection procedure and methods of analyses used ha~e been as for the study of populations of D mela~wgaster (Misra, 1965), and so have not been described again in this paper. Salient features of these have, howevel, been briefly stated where considered necessary.

Selection in a mixed population subjected to apartheid

Abstract: A model for selection from a mixed population subjected to continuous apartheid in each generation is presented. It is supposed that the population has been initially divided into portions where self-fertilization and cross-fertilization occur. The former divides in each generation again in the same ratios, the latter being wholly cross fertilised.

Variation in conception rates due to sires in six breeds of zebu cattle

Abstract: Many measures to assess reproductive efficiency in animals have been utilised by different workers. Williams (19t9) adopted 2 years as tile ideal age for a heifer to calve which requires conception to occur at I5 months. Every month thereafter was designated as a \"breeding month\" with 12 of them being considered as the \"ideal\" calving interval. The average number of breeding months required to produce a calf was obtained by dividing the total breeding months .by the number of calves born. This was converted into a percentage by dividing 12 by the computed average number of breeding months per calf dropped and multiplying by 100. A modification of this method was employed by Spielman and .Jones (1939) for determining reproductive efficiency. Koch (1938) used a fraction representing the ratio of the cow's age to the number of calves born. Erb, Wilbur and Hilton (1940) and Rende] and Venge (196t) expressed fertility as a percentage of successful inseminations of the total given per conception. Olds, Morrison and Seath (I 949) used the number of services per conception, number of calves produced and number of months per calf as measures of reproductive efficiency. Tanabe and Casida (I949) used as an \"herd index\" the percentage of cows receiving first service for which fhrther insemination was not required within 3 months. Nonreturn to first service has been used as a measure of fertility by Dunbar and Henderson (I950, 1953), Barret, Casida and Lloyd (1948) aud Olds and Seath (1950). In big A. I. breeder's co-operatives in the U.S.A., non-return rate is widely used as a measure ot ~ fertility (Salisbury and Van Demark, 1961). Services per conception and calving interval were used as measures of reproductive efficiency by Bowling, Putnam and Ross (1940), Legates (1954.), Ahmed and Tantawy (1959), Singh (1961 ) and Jakobsen (1962). Pou et al. (1953) used (a) services per conception, (b) the number of days fl-om first service to conception and (c) the regularity of the occurrence ofoestrus as measures of reproductive efficiency. Inchiosa and Pfau (1954) used the average calving interval for assessing the breeding efficiency of daughters of sires. Rognoni and Betta (1960) made use of (a) interval f iom calving to first beat, (b) interval h 'om calving to conception and (c) the number of services per pregnancy for studying reproductive efficiency. Inskeep, Tyler and Casida (1961) counted a cow to have conceived if the lirst insemination resuhed in the birth of a living calf. Such breeding was coded as 1, breeding resulting in l~ailure to produce a living calf was coded as zero. Shannon and Searle (1962} defined conceptio~ rate as tim son-sire regression of non-return to service. In the present study, two measures of conception rates were employed. They were (l) p. ,mber of services required per conception and (2) conceptions per\" ] 00 insemina-

Inheritance of hairy pinna of the ear

Abstract: Six new pedigrees on the inheritance of hairy ear rims have been presented, which support the view that it is Y-linked. Two hypotheses as to the number of genes responsible for this trail have been put forward to explain the different degrees of hairiness, and also the differential age of onset and the increase in frequency with age.

Further studies of a Kindred having an aberrant autosome (13-15) without apparent phenotypic effect

Abstract: A girl and her father, both apparently normal, had been reported earlier as carriers of a satellited submetacentric chromosome in place of a long acrocentric chromosome. A morphologically identical chromosome has now been found in the proposita’s paternal uncle, but in neither a paternal cousin nor a paternal great uncle. Clinical studies of the proposita did not reveal any deviations from normality.