The chromosomes of the hystricomorphous family Ctenodactylidae (Rodentia: ?Sciuromorpha) and their bearing on the relationships of the four living genera

Karyotype studies support the view that modern genera of the family Ctenodactylidae originated in Africa. Karyotype differences between the genera are less obvious than morphological differences but coincide in relating Massoutiera to Felovia and deriving this line from the Pectinator -like ancestor which, in turn, was closely related to a Ctenodactylus ancestor. 43% of the chromosomes are standard throughout the family; 25% seem to be very susceptible to fragmentation, translocation and inversion. These changeable chromosomes are the only ones that show differences in their G-band patterns. The ctenodactylid karyotype resembles caviomorph karyotypes in its NF, predominantly metacentric chromosomes and in its nucleolar organiser, or marker, chromosomes.     

The evolution of histones

Summary The amino acid sequences of bovine histones H2A, H2B, H3, and H4 and the first 107 residues of rabbit thymus histone H1 were examined using newly developed procedures designed to detect and evaluate weak similarities (de Haën et al., 1976). Using the McLachlan scoring system, regions of statistically significant similarity were found between several pairs of the four smallest histones. The probability that this set of similarities could result simply from chance was estimated to be less than 10^–5. No similarity was found between the H1 sequence and the other histones. The results are interpreted to indicate that at least the C-terminal portions of the core histones evolved from a common ancestral protein.     

DNA contents,giemsa banding,and systematics inScilla bifolia,S. drunensis,andS. vindobonensis (Liliaceae)

DNA contents have been determined cytophotometrically in the three Central European, relatedScilla speciesS. bifolia (2n = 18, 2 x, 1 C = 6.2 pg),S. drunensis (2n = 36, 4 x, 1 C = 12.8 pg), andS. vindobonensis (2n = 18, 2 x, 1 C = 9.4 pg). The tetraploid speciesS. drunensis contains twice as much DNA as the diploidS. bifolia. However, the diploid speciesS. vindobonensis differs in DNA content fromS. bifolia by a factor of about 1.5. This difference is largely due to euchromatic DNA, although the higher DNA content inS. vindobonensis is combined with higher heterochromatin content. The data indicate thatS. bifolia andS. drunensis on the one hand, andS. vindobonensis on the other hand are phyletically well separated. Previous taxonomic conclusions from morphology as well as C-banding are thus corroborated.Evolution ofScilla and Related Genera, V.     

Chromosome numbers and rust susceptibility as taxonomic criteria inRosaceae

BothNeuradoideae andChrysobalanoideae seem rust-free. TheSpiraeoideae andPomoideae are heavily susceptible toGymnosporangium rusts. While thePrunoideae resemble theRosoideae in being vulnerable to attacks ofPuccinia species, they are additionally susceptible toTranzschelia andThekopsora, whereas theRosoideae are characteristically afflicted byPhragmidium.—It is suggested (a) to treat theChrysobalanoideae as a separate family (Chrysobalanaceae), (b) to transferDryas from theRosoideae-Potentilleae-Dryadinae to theRosoideae-Cercocarpeae, and (c) to divide theRosoideae into two main groups of tribes: (i) the rust-freeKerrieae andCercocarpeae with x = 9, and (ii) the rust-susceptiblePotentilleae, Ulmarieae, Roseae andSanguisorbeae with x = 7.     

Chromosomal differentiation withinCrocus vernus agg. (Iridaceae) in the Carpathian Mts.

Western and eastern Carpathian populations ofCrocus heuffelianus s. lat. (incl.C. scepusiensis) have 2n = 18 but differ in karyotype. While western populations are chromosomally monomorphic, eastern populations exhibit geographical karyotypic differentiation.     

Chromosomal localization of HTLV-1 viral integration sites using in situ hybridization: detection of a novel IL2R fragment

Summary The presence of human T-cell leukemia virus (HTLV-1) in patients with adult T-cell leukemia (ATL) was investigated by Southern blotting and in situ hybridization. In all seven patients, HTLV-1 provirus was detected. A large and variable number of labeled restriction fragments were observed, indicating multiple integrations. Two of the patients analyzed by in situ hybridization had two, while the third patient had three, sites of viral integration on six different chromosomes, suggesting random integration. A single site of integration was shared by two patients, which was on chromosome 10 at bands p11p15. One of these sites was on an apparently normal chromosome 10 and the other was on a derivative chromosome 10,t(10;14)(p12;g32). The interleukin 2 receptor (IL2R) has previously been localized to this region (10p14p15). The -chain of the IL2R is continuously expressed on affected T-cells in this disease. Southern blotting with pIL2R showed the presence of a novel 3.5 kb fragment in five out of the seven patients. This novel fragment has not been previously reported. No direct correlation was found between the novel 3.5 kb fragment, present in patients both cytogenetically normal and abnormal, and viral integration in the 10p11p15 region in two patients. Therefore, it is suggested that the presence of the 3.5 kb fragment and the numerous chromosomal breaks associated with this disease may not be direct results of viral integration.     

Mutation-selection equilibrium as a possible cause of an interchange chromosome polymorphism in a cultivar of rye,Secale cereale L.

Summary A persistent chromosomal polymorphism exists in a population of cultivated rye, Secale cereale (Candela et al. 1979). In order to ascertain the possible causes that maintain it, we have estimated the fitness values of structurally homozygous and heterozygous plants and the mutation rate of spontaneous interchange. The estimates of the selection coefficient against heterozygotes (s=0.15-0.40) and of the mutation rate u=6.12×10^–2 support a mutation-selection equilibrium as a likely cause of the interchange chromosome polymorphism.     

N-banding in Triticum aestivum following feulgen hydrolysis

Summary Terminal and/or interstitial N-bands were produced on the seven B-genome chromosomes and chromosomes 4 and 7 of the A-genome of Triticum aestivum cv. Chinese Spring by a modified BSG technique following a standard Feulgen preparation. The banding was accomplished by modifying the barium hydroxide treatment.     

Proposed chromosomal phylogeny for the South American primates of the Callitrichidae family (Platyrrhini)

Cytogenetic and cytotaxonomic studies (G, C, sequential G/C, and NOR banding) were performed on 110 specimens representing the four genera of South American primates of the family Callitrichidae: Cebuella (C. pygmaea), Callithrix, groups argentata (C. argentata, C. emiliae, C. chrysoleuca, C. humeralifera, C. mauesi), and jacchus (C. aurita, C. geoffroyi, C. jacchus, C. kuhli, C. penicillata), Leontopithecus (L. chrysomelas, L. rosalia), and Saguinus (S. midas midas, S. m. niger). Mitotic chromosomes are characterized, and the rearrangements distinguishing the karyotypes of the taxa are inferred from arm homologies. The results were then converted into numerical data and submitted to cladistic analysis. The following conclusions were achieved: 1) Five karyotypic classes were observed, which correspond to the five taxa studied. Differences between them are as follows: a) Cebuella (2n = 44, 10 acrocentrics, A + 32 bi‐armed autosomes, bi) and the argentata group (2n = 44, 10A + 32bi) are different from each other due to a reciprocal translocation; b) both can be distinguished from the jacchus group (2n = 46, 14A + 30bi) by a centric fusion/fission rearrangement and a paracentric inversion; c) Leontopithecus (2n = 46, 14A + 30bi) and Saguinus (2n = 46, 14A + 30bi) differ from the jacchus group by a reciprocal translocation and three paracentric inversions; and d) Saguinus is different from the others by one paracentric inversion and pericentric inversions in at least four pairs of acrocentric autosomes. 2) The cladistic analysis separates Cebus (used as an outgroup) from the Callitrichidae groups, which forms a clade. Among the Callitrichidae, marmosets (Cebuella and Callithrix) form a sub‐clade, Cebuella and the argentata group being more closely related to each other than both are to the jacchus group. Tamarins (Leontopithecus and Saguinus) are also quite close, so that if one was not derived from the other, they with the marmosets share a common ancestor. Among the tamarins, Leontopithecus is karyotypically closest to the marmosets, specifically to the jacchus group. 3) Based on the chromosome information and considering the possible direction of the evolutionary changes (primitivity or phyletic dwarfism hypothesis, previously advanced by other authors), it was possible to propose the ancestral karyotypes and to develop two alternatives for the origin, differentiation and dispersion of the callitrichid. Both proposals are plausible, but when the geographical distribution is considered, the phyletic dwarfism hypothesis seems to be the most probable. Am. J. Primatol. 49:133–152, 1999. © 1999 Wiley‐Liss, Inc.