A detailed description with reference to the identification of 19 of the 22 pachytene chromosomes of a tetraploid species of Phaseolus from Brazil is reported. The chromosomes are identified on the basis of their relative length, arm ratio, chromomere pattern, nucleolar association and presence or absence of telochromomeres or knobs. These studies also led to the realization of allosyndetic nature of pairing, chromosomal differentiation in the parental sets and nucleolus organizer suppression in the 4n Phaseolus sp. These observations indicate an allotetraploid origin for the species. The somatic chromosomes fall into nine classes with respect to their differences in length, arm ratio and nucleolar association.
1. The separation of DNA as a double primary relational helixen seems more naturally explained by the reeling hypothesis than by the unwinding hypothesis. 2. The separation of chromosome as a double multicoiled helixen could be shown by its mathematical model and visualized by the aid of an electronic computer system. 3. The replication of DNA (Fig. 15a) may be explained as follows: a. Breaking of the bonds in the original double strands of DNA (Fig. 15b). b. While the two parent strands remain relational, daughter strands will be created along the parent strands (Fig. 15b, c), so that each pair of the parent-daughter strands thus formed is parallel, though the two parentdaughter strands are relational with each other (Fig. 15c). c. Then by reeling in, each pair of the parent-daughter strands (Fig. 15c) becomes relational (Fig. 15d, d'), and at the same time, such two parent-daughter strands become parallel with each other (Fig. 15 d, d'). d. Hence, two newly-created parentdaughter strands: two DNA's, each consisting of a double primary relational helixen, are separated without so-called unwinding (Fig. 15d, d'). 4. A chromosome consisting of a densely packed multicoiled DNA may be an inevitable form for long DNA separation, instead of the elongated form.
The salivary gland chromosome maps for Anopheles crucians and Anopheles bradleyi are described, and proposed as “standard” maps for these species. Confirming the morphological and taxonomic data, the salivary maps suggest that these species are quite closely related, differing by probably no more than five paracentric inversions, one in the X, one in 2R, two in 3R and one in 3L. The banding patterns in the X chromosomes are more similar than seen in any anophelines thus far studied. The autosomal banding patterns in both species are clearly of the type characteristic of the subgenus Anopheles. Comparisons of the banding pattern homologies with other North American anophelines, especially with A. freeborni, are detailed.
A higher incidence of chromatid breakage was observed in human peripheral blood cultures derived from three individuals under phenothiazine treatment as compared to those derived from four normal, healthy individuals. The phenothiazines involved in the study are chlorpromazine (thorazine) and trifluoperazine hydrochloride (stelazine). The mean per cent breaks in the cultures derived from treated individuals was 27.2±6.68 while in cultures derived from control individuals, it was 10.2±1.54 indicating that either or both phenothiazine drugs may affect the cell in vivo in an adverse manner. In the course of this study, it became necessary to develop a somewhat detailed method for the identification of chromatid breaks.
The cytological studies in three species of the genus Cucumis, one species and one cultivar of the genus Citrullus have been carried out. The possibility that the base number seven, the lowest in the family, has given rise to the base number 12 by fragmentation or the latter has given rise to the former by reduction in the genus Cucumis, has been analysed and discussed in this paper. In the genus Citrullus polynemy has been assumed for the difference in the size of the chromosomes. As regards the phylogenetic relationship between the two taxa, it is suggested that C. vulgaris var. fistulosus should be given a distinct specific rank, because of distinct differences in total chromatin matter, chiasmata frequency and breeding behaviour.
Tabernaeynontana cornaria Willd., a common cultivated shrub with white flowers, fragrant at night, bears fruits and sets seeds in sub-Himalayan tract. But in the plains of Uttar Pradesh (India), the plants are completely fruitless. The investigations into the causes of fruitlessness has revealed irregularities in the development of male gametophyte. All the plants scrutinized showed the haploid chromosome number to be n=11. Chromosomes during diakinesis and metaphase I were mostly paired but precocious separation of 1 to 3 bivalents was frequent. Later stages of meiosis showed laggards, unequal distribution, bivalent bridges and polyspory. These anomalies account for pollen variability and to some extent for sterility. The tapetum of microsporangium failed to show typical cataclysmic mode of development of angiosperms. Instead, tapetum was seen to persist even after the microspores had aborted. This delay in degeneration of tapetum could account for complete sterilization of pollen grains. Difference in the temperature and photoperiod in sub-Himalayan tract and the plains of Uttar pradesh seem to be responsible for pollen sterility and consequently to fruitlessness.
The present study examined the distribution pattern of the sex chromatinlike body (sd-body) in the liver, heart, kidney and spleen of chicken embryos, relating it to the embryo's sex. The embryos ranged in age between 8 and 18 days; some post-hatched chicks were also involved. The results showed that; 1. The frequency of the scl-body was the highest in the female in all of the tissues studied, except the spleen obtained from 12-day old donors. 2. In females, the characteristic pattern was for a single scl-body per nucleus. In males, the doublet heterochromatins were 2-4 times as numerous as in females. 3. As embryos developed, the incidence of the scl-body in females decreased to the male level. 4. Mitotic activity and frequency of the sd-body in a tissue were directly associated.
We have examined the feasibility of using the mitotic activity of human lymphocytes in vitro as an index for determining cytotoxicity. Untreated replicate cultures agreed closely in mitotic index if the initial cell inoculum was in the range of 0.6 to 1.0×106 cells/ml of culture medium. Smaller size inocula led to erratic results in mitotic index and low mitotic indices. Microcultures, made with two drops of whole blood, yielded mitotic indices lower than was convenient to use in testing for cytotoxicity, although replicate cultures showed good agreement in mitotic activity. Mitotic indices varied between donors but also varied in the same donor when blood was drawn on different days. Several chemical agents were used to test the sensitivity of the system to inhibition over a 24 hour period. Mitomycin C completely inhibited mitosis in the concentrations used (1.0 and 0.1μgm/ml), bacitracin did the same in high concentration (500 units/ml) but lower concentrations were less inhibitory. Fluorouracil and fluorodeoxyuridine inhibited growth 60 or 70% during 24 or 6 hour periods of treatment but did not inhibit at all during the last three hours of growth. The late-S or G2 phase of the lymphocyte cell cycle are insensitive to mitotic inhibition with either FU or FUdR. The mitotic activity of lymphocyte cultures has been found to be a suitable criterion, if judiciously employed, to study cytotoxicity and to measure events in the cell cycle that serve as prerequisite for mitosis.
A detailed meiotic study of the species P. bracteata has been carried out which is being reported for the first time. The number is reported to be n=9 for the species. The presence of one trivalent, one univalent and rest bivalents has been seen in the 15% of the PMCs analysed. It is discussed that reciprocal translocation involving a part of segment of a pair of non-homologous chromosome might be the possible reason for the trivalent formation. A segregation of 9+9 and 8+10 of the chromosomes has been observed at anaphase I, and it is suggested that the gametes with variable number of chromosomes may be involved in the origin of different base numbers in the genus. Laggards, bridge and fragments are also seen and a pollen sterility of 19% is recorded. Evolution of this diploid species is suggested to be due to translocation from related species. A breeding test is proposed to elucidate the knowledge further.
The present study deals with the incidence and distribution of sex chromatin body, drumstick and sessile bodies in two pairs, each of Gallus domesticus, Columba livia and Passer domesticus. Somatic tissues, i.e. liver, duodenum, skin and blood from both sexes were examined. For liver, duodenum and skin interphase nuclei, Feulgen and BS-FG methods were applied and Leishman and Giemsa stains were used for blood. The incidence of sex chromatin was more in females than in males in all the tissues. Incidence of drumsticks and sessible bodies was found to be more in males than in females. The drumsticks were associated with homogametic sex, whereas the sex chromatin body with female sex only. Although the properties of sex chromatin body and drumsticks were not similar and they were differently associated with sex, still the sexual dimorphism at the cellular level was so distinct that it seemed worthwhile to use it as a basis for genetic sex determination in the species of birds studied. The results have been analysed statistically by applying chi-square test with highly significant results.
By examining the cells of the endothecium and exothecium of Allium cepa anthers we have been able to study the formation and development of the vacuoles. These appear to arise from local expansions of the ER which, in the course of cell differentiation, increase in size until they form one single vacuole occupying most of the cell volume. The three phases in the development of the vacuoles, local expansions of the ER provacuoles, young or star-shaped vacuoles, and fully developed, or spherical vacuoles, take “pari passu” with the differentiation and elongation of the parenchyma of the anther.