Showing papers in "Chromosoma in 1963"

Differentielle DNS-Replikation in den Speicheldrüsen-Chromosomen von Chironomus thummi

Abstract: Nach Injektionen der Larven des Bastards Chironomus thummi thummi × Chironomus thummi piger mit H3-Thymidin, sowie C14-Thymidin und H3-Thymidin in zeitlichem Abstand, wird der Verlauf der DNS-Synthese in den Speicheldrusen-Chromosomen autoradiographisch analysiert. Der DNS-Replikationsschritt beginnt gleichzeitig in allen Querscheiben mit einer gleichmasigen Thymidin-Aufnahme. In der Endphase ist die DNS-Synthese nur noch in den heterochromatischen Strukturen nachweisbar. Alle ubrigen Querscheiben haben in einer festliegenden Folge die DNS-Synthese fruher beendet.

Geschlechtschromosomen und Geschlechtsbestimmung bei einigen Calliphorinen (Calliphoridae, Diptera)

Abstract: 1. Es werden das Verhalten der Chromosomen in Spermatogenese und Oogonienmitosen sowie die Geschlechtsbestimmungs-Mechanismen folgender Arten der Unterfamilie Calliphorinae (Diptera) untersucht: Chrysomyia albiceps, C. rufifacies, C. megacephala, Lucilia sericata, L. cuprina dorsalis, L. illustris, Cynomyia mortuorum, Calliphora vomitoria, C. erythrocephala und Phormia regina; von Lucilia caesar wurde ausschlieslich, bei den anderen Arten erganzend der Chromosomenbestand der Neuroblasten untersucht. 2. Chrysomyia albiceps und C. rufifacies zeichnen sich durch ihre monogene Fortpflanzungsweise aus; alle anderen Arten sind amphogen. 3. Monogene und amphogene Calliphorinen besitzen die gleiche Chromosomenzahl (2n=12) sowie strukturell ahnliche Chromosomensatze und zeigen prinzipiell gleiches Chromosomenverhalten. 4. Alle Arten weisen neben 5 grosen euchromatischen, medio- bis submediokinetischen Chromosomenpaaren 1 Paar partiell oder total heterochromatischer Chromosomen auf, die bei den amphogenen Species mit Ausnahme von Calliphora erythrocephala im ♀ heteromorph (XY) und im ♂ gleich (XX), bei Calliphora erythrocephala und den monogenen Chrysomyia-Arten dagegen in beiden Geschlechtern homomorph sind. 5. Die Spermatogenese aller Calliphorinen verlauft achiasmatisch. 6. Durch die streng geschlechtsgebundene Vererbung rontgeninduzierter Y-Autosom-Translokationen wird die Geschlechtschromosomennatur der Heterochromosomen von Phormia regina und Lucilia cuprina dorsalis nachgewiesen; alle grosen Choromosomen von P. regina weisen einen geschlechtsunabhangigen Erbgang auf. 7. Das Y-Chromosom von Phormia regina enthalt einen epistatischen ♀-Differentiator; im Y-Translokationsstamm auftretende XXY-Ausnahmetiere sind stets mannlich, XO-Ausnahme-Individuen morphologisch normale und fertile ♀♀. Das Vorkommen eines XO- ♀ bei Lucilia cuprina dorsalis bestatigt auch fur diese Art die geschlechtsentscheidende Rolle des Y-Chromosoms. 8. Die kleinen heterochromatischen Chromosomen von Calliphora erythrocephala haben keine Geschlechtsbestimmungs-Funktion mehr; diese wird von einem grosen, morphologisch undifferenzierten Chromosomenpaar ausgeubt. 9. Dem XY-Geschlechtsbestimmungs-Mechanismus aller amphogenen Calliphorinen entspricht das 1:1-Verhaltnis der Geschlechter in Geschwisterschaften. 10. Bei den monogenen Arten Chrysomyia albiceps und C. rufifacies uben die kleinen heterochromatischen Chromosomen ebenfalls keine Geschlechtsbestimmungs-Funktion mehr aus. 11. Thelygenie (♀♀-Erzeugung) und Arrhenogenie (♂♂-Erzeugung) sind Eigenschaften der ♀♀; die ♂♂ haben keinen erkennbaren Einflus auf das Geschlecht der Nachkommenschaft. Die uberwiegende Mehrzahl der gepruften Nachkommenschaften thelygener ♀♀ zeigt eine statistisch gesicherte 1:1-Aufspaltung in thelygene und arrhenogene ♀♀. 12. Die Monogenie wird mit der Annahme erklart, das die thelygenen ♀♀ heterozygot fur einen dominanten weiblichen Geschlechtsrealisator (F′) mit pradeterminativer Geschlechtsbestimmungs-Wirkung und die arrhenogenen ♀♀ wie die ♂♂ homozygot fur das rezessive Allel (f) sind.

Die Funktionsstrukturen des Y-Chromosoms in den Spermatocytenkernen von Drosophila hydei, D. neohydei, D. repleta und einigen anderen Drosophila-Arten

Abstract: Inhalts i ibersicht se~e I. Einleitung . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207 II. Material und Meghode . . . . . . . . . . . . . . . . . . . . . . 208 III. Ergebnisse . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 1. Allgemeine Merkmale der Kernstruk~uren yon D. hydei und D. neohydei 209 2. Chromosomale Funktionsstrukturen yon D. hydei und D. neohydei. . 215 a) Komponente 1 : Die zwei ,,Faden" . . . . . . . . . . . . . . 215 b) Komponente 2: Die zwei ,,Keulen ~ . . . . . . . . . . . . . . 219 c) Kompone~te 3: Der ,,Pseudonukleolus" yon D. hydei und das ,,distale Kn~uel" yon D. neohydei . . . . . . . . . . . . . . 223 d) Komponente 4: Die ,,proximalen Kn~iuel" . . . . . . . . . . . 226 3. Histochemische Untersuchungen . . . . . . . . . . . . . . . . 227 4. Der Abbau der Funktionsstrukturen wShrend der sp~ten Prophase . . 231 5. Der Bau der Spermatocytenkerne yon D. repleta . . . . . . . . . . 233 6. Untersuchung der Spermatocytenkerne weiterer Drosophila-Arten . . 239 IV. Deutung der Funktionsstrukturen des Y als Sehleifenpaare eines Lampenbfirsten-Chromosoms . . . . . . . . . . . . . . . . . . . . . . . 242 V. Diskussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253 Literatur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

The salivary gland chromosomes of Drosophila hydei Sturtevant

Abstract: A cytological map of Drosophila hydeiSturtevant, one of the species of the repleta group, is presented together with some cytological observervations, including the description of three X-ray-induced rearrangements.

A mitotically unstable supernumerary chromosome with an accumulation mechanism in a grasshopper.

Abstract: A population of the grasshopper Calliptamus palaestinensisBdhr. from near Jerusalem, Israel was analyzed cytologically. Twenty-two percent of the males had extra heterochromatic chromosome segments or supernumerary chromosomes. The extra segments were present in either a heterozygous or a homozygous condition and in frequencies similar to those expected according to the Hardy-Weinberg law.

Genome analysis in Triticum zhukovskyi, a new hexaploid wheat

Abstract: 1. The karyotype of T. zhukovskyi, a hexaploid wheat recently recorded from Western Georgia of the U.S.S.R., revealed that it has 3 pairs of satellited chromosomes. Two of these resemble closely the two pairs present in T. timopheevi. The other pair is similar in arm ratio to the pair found in T. monococcum var. hornemanni. Micro-satellites usually found in varieties of T. monococcum did not occur in T. zhukovskyi. 2. A maximum of 4 quadrivalents per cell was found at meiosis in T. zhukovskyi, the average being 1.35 per cell. Pollen and seed fertility were normal. 3. In crosses between T. zhukovskyi and T. spelta, T. macha and T. vavilovi, only the F1 plants of the cross with spelta survived. There was an average frequency of 15.1 univalents per cell in the zhukovskyispelta hybrid. Thus, the partial failure of chromosome pairing in this hybrid is similar to that usually found in hybrids between T. timopheevi and other tetraploid species. 4. From a discussion of the data, it is suggested that T. zhukovskyi might have arisen through chromosome doubling in the hybrid T. timopheevi × T. monococcum var. hornemanni. If this conclusion is supported by future experiments, T. zhukovskyi will be the first hexaploid wheat to have a genomic constitution other than ABD.

Chromosomal study in patients with cysts of the jaw, multiple nevoid basal cell carcinomata and bifid rib syndrome.

Abstract: A chromosomal abnormality in a patient with cysts of the jaw, recurrent nevoid basal cell carcinomata and bifid ribs is described. The patient presented a normal female complement, except for the unusual length of one arm of one of the chromosomes No. 1. Her mother, two sisters, and a male child of one of these two sisters presented a similar chromosomal anomaly with no expression of the syndrome. Several possible explanations are discussed.

Cytogenetics of the grasshopper Moraba scurra. VIII. A complex spontaneous translocation.

Abstract: The cytology of a male individual of the grasshopper Moraba scurra which was heterozygous for a complex translocation involving breaks in four different, non-homologous, chromosomes, is described. Chains of up to eight chromosomes occur at first metaphase. Certain chromosomes which never normally show more than a single chiasma form two chiasmata with a fairly high frequency in this individual.

Meiotic parthenogenesis and heterochromatization in a soft scale, pulvinaria hydrangeae (Coccoidea: Homoptera)

Abstract: Meiotic parthenogenesis of a type not previously described was found in Pulvinaria hydrangeaeSteinweden. During diakinesis 8 bivalents were formed. At prometaphase the spindle was tripolar but anaphase I was bipolar and normal. After completion of division of the primary oocyte, the following sequence occurred: 1. polar body I divided, usually into 3 products; 2. the secondary oocyte divided to yield the egg pronucleus and polar body II; 3. the egg pronucleus divided into its two haploid products; and 4. the second polar body divided. The products of the egg pronucleus fused while dividing to restore the diploid chromosome number; this division may be equated to the first cleavage division. The products of the polar bodies did not take part in the formation of the embryo proper or the mycetocytes.

Spontaneous interchange in Chorthippus brunneus

Abstract: 1. The meiotic behaviour of a male of Chorthippus brunneus (2n=16+X) is described whose germ-line was uniform in respect of a single interchange. 2. The sub-equal interchange was between a long, metacentric (L3) and the longest of the medium-sized acrocentric chromosomes (M4). The interchange points were equidistant from the centromere and the segments involved were at least as long as half the length of the arms involved. 3. Chains of four predominate. Chiasma formation was not observed in one of the interstitial segments and was uncommon in the other. The multiples showed only ca. 30% alternate orientation while adjacent homologous orientation was observed in over 50% of the cells. Chains with adjacent non-homologous orientation were not seen. 4. Although the relative frequency of adjacent homologous and adjacent non-homologous orientation recorded here is in the opposite direction to that found by Burnham in maize, the two sets of data are comparable because the structure of the chains is different in the two cases. 5. The role of structural changes and the probability of their becoming established is discussed. In this connection both their immediate prospects and their subsequent utility have to be considered. It is suggested that the maintenance of super-genes after crossing structurally different chromosome homozygotes may be more important than hybrid sterility in maintaining their genic dissimilarity. And protecting a super gene from recombination prior to its fixation in the homozygous condition may be more important in the origin of species than maintaining it by hybrid sterility afterwards.

The Comstockiella system of chromosome behavior in the armored scale insects (Coccoïdea: Diaspididae)

Abstract: The Comstockiella chromosome system occurs in the armored scale insects and the closely allied palm scales. During development of the males, the paternal chromosome set becomes heterochromatic and remains so until spermatogenesis. With the exception of one chromosome, the heterochromatic complement loses its differential aspect during early spermatogenesis and its members pair with their euchromatic homologues There is but one division during which the two components of each bivalent separate to opposite poles. Both division products form sperm.

A quantitative study of chromosomal elasticity and its influence on chromosome movement.

Abstract: Chromosome elasticity and movement have been studied in living cells in two distinct situations: early anaphase stretch due to opposed external forces, and drag stretch — an elongation due to frictional resistance or drag on a chromosome being pulled toward one pole. Drag stretch provides a simultaneous display of both friction and elasticity and shows that chromosomes in living cells are elastic up to approximately six-fold increases in length.

The W-chromosome of the budgerigar, Melopsittacus undulatus

Abstract: The chromosome complement of male and female budgerigars (Melopsittacus undulatus) was studied in primary kidney cell cultures. van Brink's description of the male complement was confirmed. The 26 largest chromosomes can unequivocally be placed in 13 pairs. In the female the fifth largest chromosome is single ; it is the Z-chromosome, again confirming van Brink. In addition in all females and none of the males a previously undescribed extra chromosome was found, in size between pairs 9 and 10 with arm ratio 1∶1.5 and negatively heteropycnotic at metaphase. It is identified as the W-chromosome.

Meiosis in garden roses

Abstract: Meiosis in 96 varieties of garden roses was studied. While the euploid numbers were most frequent, in exceptional cases, aneuploid numbers were recorded. Intervarietal variation in chromosome pairing is reflected in the varying degrees of expression of univalents, heteromorphic bivalents, bivalents with double secondary constrictions and multivalents. Supernumerary fragments in addition to the euploid chromosome complement were recorded in three varieties. Three varieties of floribundas and one of hybrid polyanthas were chromosome numerical mosaics.

A long Y chromosome in man.

Abstract: An unusually long Y chromosome was described in the phenotypically normal father and paternal grandfather of a girl with Down's syndrome, and likewise in a male infant with multiple malformations and his father, normal in phenotype. Measurements revealed that the long Y chromosome corresponded in length to autosomes of group 16–18.

The chromosomes and relationships of Welwitschia mirabilis

Abstract: W. mirabilis is unique in the plant kingdom by having a very peculiar habit. Its karyotype is very asymmetrical. Two of the chromosomes in the complement are satellited and this coincides with 2 nucleoli in the metabolic nuclei. The longest pair in the complement is nearly 3.25 times longer than the shortest pair. Between the two extremes there is a gradual transition in size in the karyotype. Such a karyotype has no relation (quantitative or qualitative) with those in Ephedra and Gnetum. Arguments have been advanced against interrelating Ephedra and Welwitschia through hermaphrodite “flowers”. Such flowers appear to be due to the sex polymorphism ensuing as the result of tetraploidy (in originally diploid-dioecious species) and do not represent therefore the ancestral condition. Only after these abnormalities are discovered in diploids they will represent atavistic mutations and then alone phyletic reliance can be placed in them. In view of the strong morphological differences the few resemblances between the three genera are possibly due to parallel evolution, because many of these are also found in other gymnosperms. The best arrangement is to treat the three genera as belonging to three distinct orders under one class.

Cytogenetic studies following high dosage paternal irradiation in the mealy bug, Planococcus citri

Abstract: When females of the mealy bug. Planococcus citri, are mated to males previously irradiated with heavy doses of gamma rays (30,000 to 120,000 rep), the progeny is mostly female. These X1 females are gynogenetic, with unbroken chromosomes. Detailed cytology of 17 such gynogenetic females showed triploids, diploids. 3N/2N and 2N/N mosaics. Most of the embryos produced by triploid mothers were aneuploid and these degenerated before gastrulation. Regardless of aneuploidy, male embryos showed the typical lecanoid heterochromatization of the paternal set of chromosomes. Just prior to degeneration, the euchromatic chromosomes in the aneuploid male embryos showed endomitotic splitting while the heterochromatic did not. Among the progeny of 3N ♀ X 2N ♂ matings, only males with 5 euchromatic + 5 heterochromatic chromosomes and females with 10 or 15 euchromatic chromosomes were found. A search for adults with 5 heterochromatic +10 euchromatic chromosomes among the progeny of triploid mothers was unsuccessful. Chromosomal variables such as aneuploidy of the euchromatic set, haploidy and fragmentation are discussed in relation to the problems of heterochromatization of the paternal set and sex determination in this species.

Chromosome behavior of the cimex pilosellus complex (cimicidae: hemiptera).

Abstract: 1. The chromosome complement of Cimex pilosellus strain A is 24, consisting of 11 pairs of autosomes with an XY in the male and 2X in the female. 2. The chromosome complement of Cimex pilosellus strain B is 22, consisting of 10 pairs of autosomes with an XY in the male and 2X in the female. 3. The hybrid, C. pilosellus strain A (♀ ♀)xC. pilosellus strain B (♂♂), has 23 chromosomes. In diakinesis and the first metaphase the hybrids have 9 bivalents (8 of the 9 bivalents are heteromorphic), 1 trivalent, and the X and Y. In diakinesis each bivalent usually has one chiasma and a trivalent always has two chiasmata. Two kinds of second metaphase are observed as a result of the 1∶2 separation of a trivalent in the first division. One is 10A+XY and the other is 11A+XY. 4. In the hybrid, clear evidence of meiotic sequence is obtained from observation of the behavior of heteromorphic bivalents and the trivalent. The autosomes co-orient and are reductional at the first meiosis and auto-orient and are equational at the second meiosis.

Observations on dicentrics in living cells

Abstract: In previously irradiated endosperm cells of Haemanthus katherinae studied in vitro by means of micro-cinematography, two-kinetochore chromatids and dicentric chromosomes have been observed. Breaking of such dicentric chromatids and chromosomes has been analysed. Behaviour of some of the dicentric chromosomes during anaphase deserves special attention: interlocking dicentrics cut one through another and rejoin in a few minutes. In this way from a metaphase interlocking dicentric, two sister anaphase dicentrics are formed. Interlocked dicentrics can also uncoil and not break at all. In this case no activity was observed in one kinetochore of one dicentric in later stages of anaphase (two kinetochores were active in one dicentric and only one in its sister). Analysis of chromosome movements in two-kinetochore chromatids and dicentrics is also presented.

The mode of meiosis in the Psyllina

Abstract: 1. The spermatogenesis of six psyllids and the oogenesis of Psylla forsteri have been studied. The haploid number n=13 was found in 4 species, all with an XO system of sex determination. 13 may well be the modal haploid number in the genus Psylla. 2. The chromosome complement of the only XY species, Psylla corcontum, with n=11, is probably the result of two chromosomal rearrangements which have led to the formation of a neo-XY pair. 3. Psylla forsteri is an XO species in which the haploid set consists of only 8 chromosomes, one of which is very large. As the amount of DNA in this species is approximately equal to that in the 13-chromosome species P. sorbi, the large chromosome obviously corresponds to 5 or 6 chromosomes of P. sorbi. 4. A diffuse stage, which leads to a considerable increase of nuclear size, is typical of late pachytene to late diplotene of spermatogenesis. 5. In contrast to the other cytologically studied Homoptera Sternorrhyncha, the bivalents of psyllids co-orientate at the first metaphase of spermatogenesis. The following anaphase is therefore prereductional. 6. In the oogenesis of Psylla forsteri the bivalents always seem to have auto-orientation, which means morphological postreduction at first anaphase. 7. The karyological picture is that of an organism with a diffuse kinetochore. 8. The Hemiptera and the plant genus Luzula both have diffuse kinetochores. The reason that the chromosome numbers in Hemiptera vary far less than in the genus Luzula may lie in the existence in the Hemiptera of a delicate system of sex determination sensitive to any change in chromosome number and structure. 9. Cytologically, the Psyllina lie between the suborders Sternorrhyncha and Auchenorrhyncha.

Kontrolle des crossing over vom temperatur-bedingten Allozykliegrad und vom α-Heterochromatin des X-Chromosoms bei Phryne cincta

Abstract: 1. In populations of the dipteran Phryne cincta (2n = 6+XX♀, XY♂) several X-chromosomes of different structure are present. These are allocyclic in contrast to the (eucyclic) autosomes, as seen in their behaviour in mitosis and meiosis and in their varied appearance in polytene nuclei (comp. Wolf 1950, 1957). 2. The polytene autosomes (2–4 s. Pig. 7) differ from each other in easily recognizable characters and form no chromocenter. The polytene X-chromosome is always relatively much shorter than the autosomes and more or less β-heterochromatic (granular or indistinctly banded) in larvae, raised at room temperature. In larvae raised at low temperature (0–4° C) it passes through a morphogenesis, growing to normal or nearly normal length and assuming the aspect of an euchromatic element (comp. X a in Figs. 3 and 4). 3. Two stocks, characterized by different X-chromosomes, symbolized by Xa and Xb or a and b respectively, were chosen for the experiments. In mitosis both these X-chromosomes are rod-like, a is as long as autosome 4, b has only half its length (Figs. 1, 2a–d). 4. Just before pupation, in polytene nuclei of larvae raised at low temperature a and b are of almost equal length. They differ from each other in several inversions and in the appearance of two large α-heterochromatic bands in a (α2 and α3, Fig. 5; “α-quantum-difference”). 5. The α-bands, especially the large block α2, show a considerable intercellular variation in their relative DNA-content (measured as length of the α-element). The mean DNA-content is negatively correlated with the degree of stretching of the chromosome (Table 1). 6. In polytene nuclei of female hybrids from the crosses aaxbY or bbxaY, a and b are unpaired or incompletely paired in variable degrees (Figs. 7, 8a–e). The heterozygotic chromosome pair can be devided into 5 segments (I–V, Fig. 6), three of which are marked by clearly defined structural differences (I, III, V). 7. The pairing-segments II and IV, exhibiting an identical and parallel sequence of discs in a and b, allow six crossing-over recombinations (cb, db, eb, fb, gb, hb; comp. Figs. 9, 10). These new types of X-chromosomes occur in very different frequencies in the progeny of the hybrid ♀♀ when backcrossed to standard ♂♂ bY. The types eb and fb occur relatively rarely, while gb and hb are extremely rare (Figs. 9, 10, Table 2); in 70% of the progenies they are not present. The recombination-process is mainly restricted to pairing segment IV. 8. In a and in the crossover-chromosomes c, e, g very often a threadlike constriction appears in the region of α2, resulting mostly in a pseudofragmentation with more or less independent location of the two chromosome parts (Figs. 3d, 8f-i, 11a). A variety of kinds of fusion between the parts and the autosomes, especially in their α-heterochromatin, is possible (Figs. 3e, 8g–i). 9. Lowering the breeding-temperature increases the duration of development, the size of the larvae, and the lengthening and euchromatization of the β-heterochromatic parts of the X-chromosomes. In the hybrids it also results in increasing the recombination rate (Table 3 and 4). 10. In the main experiments, hybrid offspring from the same parental pair, were raised at different temperatures: some individuals at high (20–26° C), others at low temperatures (2–8° C). The resulting two series of imagos were kept in optimal or room temperatures (14–22° C). The female progeny of 23 hybrids raised at elevated temperature and of 27 hybrids raised at low temperature, i.e. 1766 and 2102 X-chromosomes respectively, have been tested (Table 5, Fig. 12). No or only little recombination occurred in hybrids raised at 20–26° C (mean = 2.4%) in contrast to their sisters raised at 2–8° C, which gave a relative high frequency (mean = 18,2%). 11. In these cases only the first egg batches of each hybrid ♀ have been evaluated. Later progeny exhibits a reduction in crossing-over frequency in cold-raised hybrids with growing age. The mean rate of recombination of 14 hybrids is lowered from 16,6% in the first to 7,1% in the following progeny (n=1813; Table 6, Fig. 15) presumably as a consequence of keeping the imago in higher temperature. 12. The results from several larger groups of cold-raised sister hybrids more or less clearly demonstrate a bimodal distribution of recombination values (Fig. 13) suggesting a difference in recombination potentiality between the two X-chromosomes in the mother of the hybrids. Some data indicate the recombination rate in the X-chromosome as negatively correlated with the rate of development (Table 7). 13. The Mendelian ratio, 1∶1, of the non-recombinant types, ab and bb, is found in the progeny of the warm-raised hybrids (1769∶1778). This ratio is shifted considerably in favour of type ab in the case of low temperature hybrids (1996∶1626). In the recombinant types, cb and db, the ratio is always markedly shifted in favour of cb, irrespective of temperature (712:343). There must exist a causal relation between the Mendelian anomaly and the recombination process the nature of which is yet unknown. 14. The temperature at which a larva is raised effects both the frequency of crossing over and the stretching and euchromatization of β-heterochromatin in the polytene X-chromosome. This parallele suggests that structural changes comparable to those in the polytene chromosomes are induced by low temperature in meiotic chromosomes as well, and that these changes are responsible for the effect on the crossing-over frequency. These changes, which are reversible by age or temperature, are supposed to cause the extention of the “effective pairing” (as in euchromatic segments) on β-heterochromatic elements, which normally are unpaired. 15. The so-called “α-quantum-difference”, i.e. the difference in the amount of α-heterochromatin (or in the “relative DNA-content”) between the X-chromosomes is considered to be causally related to the crossing-over process (“α-differential-effect”). By way of a potential function it effects crossing over not only within the “α-differential” tetrad but also crossing over in non-homologous and unrelated pairs of chromosomes in the same meiotic cell. 16. This hypothesis was ascertained by two independent inversions in autosome 2 (In 2a and In 2b, Fig. 16) which permitted to test the influence of the “α-quantum-difference” in the X-chromosomes on crossing over in the autosome. In preliminary studies the progenies of 8 females (ab, bb, cb) and 3 males (aY, cY) of the heterozygous F1 backcrossed to homozygous b-stock have been investigated. In the progeny of the males only the parental combinations in autosome 2 were found. In the test cross progeny of the females the two expected types of recombination appeared (with only one inversion, In 2a or In 2b), but there existed a very high difference in linkage between bb- ♀♀ on the one side (3.6% crossing over) and ba- and bc-♀♀ on the other (40.2% crossing over).

A spontaneous interchange in chorthippus brunneus with extensive chiasma formation in an interstitial segment

Abstract: 1. A spontaneous interchange is described between the metacentric L1 and the acrocentric M5 members in a male of Chorthippus brunneus (2n=17). The interchange is markedly unequal and leads to the production of two new categories of chromosomes 15 and 51 which are readily distinguishable both at mitosis and meiosis. 2. In 85% of the cells examined the interchange was present as a chain of four multiple. 58% of these chains had a chiasma in the longer of the two interstitial segments produced as a result of the interchange. A further 38% of them had a chiasma in the homologous minute arms of their acrocentric members. In the remaining 4% chiasmata were absent from both these segments. 3. The orientation behaviour of these chains is predominantly nondisjunctional. Only the 4%, where chiasmata are completely absent from the arm common to the acrocentric 51, 5 members, succeed in orientating in an alternate manner. Fertility is therefore expected to be low. 4. Where chiasma formation is restricted to the pairing segments only, the pattern of orientation shows a correlation with the chain type.

Electron microscope studies on salivary gland cells: II. The nuclear envelope of Bradysia mycorum prey (Sciaridae)

Abstract: A study of the ultrastructure of the nuclear envelope of the salivary glands cells in the sciarid Bradysia suggests that it probably consists of four membranes, instead of two as found in most cells. The fine structure associated with the pores closely resembles that described in amphibian oocytes by Wischnitzer 1958.

Studies on supernumerary chromosomes in the genus Dactylis

Abstract: 1. In Dactylis glomerata subsp. lusitanica some populations were found to have supernumeraries. These supernumeraries were somatically stable, heterochromatic and had sub-median centromeres. At metaphase I they were about half the size of the smallest euchromatic chromosomes. 2. At diakinesis and metaphase I, the supernumeraries formed bivalents and multivalents in moderately high frequency. Some multivalent configurations had triple-chiasmata. There were no differences in the chiasma frequencies in supernumeraries between various genotypes with two supernumeraries except in the case of comparisons involving the asynaptic plant. The two genotypes with 4 supernumeraries also did not differ in this respect. 3. In plant Dgl 585-3 (2n+3s) the chiasma frequency in supernumeraries differed highly significantly in two years, while with respect to the normal set the differences were insignificant. 4. Anaphase I separation was studied in plants with one and two supernumeraries. In plants with one supernumerary both non-disjunction and the division of the univalent supernumerary were found. In plants with two supernumeraries the two supernumeraries on the whole disjoined regularly to the two poles. In the asynaptic plant (2n+2s), where the two supernumeraries were present as univalents in most of the cells, in only one cell out of 72 had one of the supernumeraries divided. The data on lagging supernumeraries at both the meiotic divisions, indicate a correlation between the extent of pairing of supernumeraries and a reduction in frequency of laggards. Thus in this respect they resemble the normal set. 5. Data were also collected with respect to the position of the univalent supernumerary on the spindle at metaphase I and the effect of supernumeraries on morphological characters and pollen fertility. 6. Asynapsis seems to affect the supernumeraries much more than the normal chromosomes. A higher frequency of non-chiasmate associations between supernumeraries and the normal set was found to be associated with asynapsis. In spite of a very low pairing in supernumeraries under the influence of asynapsis, they disjoined regularly to the poles. 7. Evidence was found for the non-disjunction of supernumeraries at pollen mitosis in Dactylis. The variance for the case when supernumeraries were transmitted from the male side was significantly higher.

Knobs in Italian maize

Abstract: A cytological survey of 425 samples of maize from all over Italy has brought to light some further knob-like structures in addition to those already known, on pachytene chromosomes 1, 3, 8 and 10 and with particularly high frequency, on 7. The general average for knob number is anyway rather low, about 2,7. The data show very few knobs on the chromosomes from the maize of southern Italy, a slightly higher number on the chromosomes of maize from central Italy, and about twice the number in north Italy. This is also true of the single knobs studied, with very limited exceptions. B-type chromosomes, although very rare, show a negative correlation with the knob number. The number and the type of knobs may be of great importance in studying evolutionary processes, as well as in breeding programs.

A nuclear body in meiosis of Bromus

Abstract: 1. A structure which is tentatively called a “nuclear body” has been observed in microsporocytes in a large number of species of Bromus. It was found in diploid and polyploid species and in species with complements of large (L-)chromosomes, medium (M-)chromosomes or L- and M-chromosomes. These species were collected in North and South America and Europe. It is suggested that the nuclear body occurs regularly in species of the genus Bromus. 2. The nuclear body was first visible at pachytene. It was generally single. In some individuals it disappeared at the end of prophase; in others it was present during later stages of meiosis, in some instances as late as the quartet. The nuclear body was not observed when the quartet cells had separated. Before it disappeared the nuclear body underwent a sudden or gradual diminution. It decreased in size, or became faint-staining and faded away; or it decreased in size and faded. The nuclear body generally disappeared at the end of prophase in the diploid and tetraploid species and was present at metaphase-I and later stages in higher polyploid species. 3. When the nuclear body was present in later stages of meiosis it behaved as follows: It was extruded from the spindle at metaphase-I and frequently came to lie in the polar region of the cell; it was not included in either nucleus at telophase-I. A single nuclear body was present in one dyad cell; it lay outside the spindle at metaphase-II, and was included in one of the cells of the quartet. 4. A very great range in the size of the nuclear body was found in early stages of meiosis. Some variation in size was found within individuals and among individuals of the same species. Present data indicate some relationship between chromosome number and size of the nuclear body. The largest nuclear bodies were found in duodecaploid and octoploid and the smallest in diploid species; however an exact correspondence was not observed. 5. The nuclear body is extremely variable in shape. It has a vesicular appearance; there is great variation in the number, size and staining of the vesicles. The appearance of the nuclear body may vary within and among anthers and individuals. 6. The nuclear body is not associated with the nucleolus at pachytene, nor with the nucleolar organizing regions of specific bivalents. The nuclear body is often touching a bivalent or attached by fine strands to a bivalent during prophase. However, there appears to be no specifically differentiated region of any bivalent with which it is generally associated. The nuclear body may be associated with terminal or interstitial regions of bivalents which differ in size or chromomere pattern. It was more frequently associated with bivalents in some individuals than others. 7. The nuclear body was not found in mitotic divisions in shoot or root tips and thus appears to be related specifically to the meiotic divisions. It may arise as an exudate from some chromosomes, or it may be extruded from the nucleolar material; it seems less likely to arise from the karyolymph. It may be composed of some materials discarded in preparation for meiosis or during its earliest stages, which are perhaps related to concurrent changes in chromosome organization. 8. Observations are considered which suggest that a structure similar to the nuclear body observed in Bromus may be present in other plant genera.

Cytotaxonomy of the genus Smilacina (liliaceae)

Abstract: Summary1.The chromosome number of three North American Smilacina species was determined as 2n=72 for S. racemosa, and 2n=36 for S. stellata and S. trifolia. Octoploidy (2n=72) in S. racemosa had previously been unreported for both this species and the genus.2.The karyotype of these three species was analyzed, as follows: S. racemosa: K (2n) = 72 = 14 V + 24 J + 34 v (or 4 j + 30 v); S. stellata: K (2n) = 36 = 6 V + 14 J + 10 v; S. trifolia: K (2n) = 36 = 4 V + 16 J + 10 v. Karyotypic affinity between S. stellata and S. trifolia is great, substantiating a phylogerietic relationship already indicated by morphological similarity.3.The taxonomic problems of the morphologically as well as karyologically heterogeneous S. racemosa complex is briefly discussed in relation to cytology. All Wisconsin collections proved to be octoploid with 2n=72. The exact taxonomic position or geographic origin of the plant called “racemosa” by Therman (1956), in which 2n=36 chromosomes were counted, is unknown. It was not possible to establish as yet whether or not there is any definite correlation between karyology and morphology in this group, in effect between tetraploidy vs. octoploidy on the one hand and the poorly defined morphological varieties cylindrata in the south vs. racemosa in the north. Whether the octoploid arose from autoploidy out of the southeastern populations, or from amphiploidy as a result of the latter crossing with a western postglacial immigrant are two possibilities that are discussed but not verified. The S. racemosa complex promises to be a rewarding object of cyto-geographic analysis.

Cytologie de la Pseudogamie chez Luffia lapidella Goeze (Lepidoptera Psychidae)

Abstract: The bisexual species Luffia lapidella has a pseudogamic (or gynogenetic) form, which is thelytokous and very similar to the parthenogenetic L. ferchaultella, but its egg needs the stimulation of the sperm. The inseminated egg restores its diploid chromosomal number in performing the same kind of restitutional first meiotic division as ferchaultella does. The second division, although already diploid, is normal and is followed by the formation of two nuclei, one of them degenerating as a polar body. The sperm starts developing as in the normal egg, but by metaphase II, it stops growing to a pronucleus and remains as a contracted and pycnotic body. Although attracted by the central female nucleus, it does not fuse with it. The male centriole behaves normally, it possibly plays a role in the first cleavage mitosis. The egg divides diploid and without any paternal chromosomes.