Pairs Of Metacentric Autosomes Research Articles

Mitotic metaphase karyotype of the mosquito Anopheles arabiensis Patton (Diptera: Culicidae) from Kassala State, eastern Sudan

The mosquito Anopheles arabiensis Patton is the most important malaria vector in Sudan. The study was conducted for the first time to describe numerically the karyotype of An. arabiensis from Kassala State, eastern Sudan. Adults An. arabiensis were caught from human dwellings during the rainy season of 2022. We examined for the first time the utility of brain ganglia tissues of adult mosquitoes for mitotic chromosomal preparations using Giemsa stain - spreading technique. High-quality chromosomal preparations were examined and photographed. Chromosome measurements were carried out using computer software and analyzed statistically using SPSS® software. The diploid mitotic chromosome complement of An. arabiensis consists of three pairs of chromosomes, two pairs of metacentric autosomes (chromosome II and chromosome III) and one acrocentric dot-shaped pair, sex chromosome, which is homomorphic in females (XX) and heteromorphic in males (XY). Chromosome II was described as the longest (2.61±0.07) of the complement and constitute 44.39% of the total length (5.88 μm) of the haploid chromosomes set, while chromosome I (X=1.39 ±0.04; Y=1.04±0.04) as the shortest chromosome. Chromosome X appears in the males significantly larger than chromosome Y (P = 0.00). Chromosome III has an intermediate length (1.88±0.06) compared with the other chromosomes. Comparison of the average lengths of the three chromosome pairs by ANOVA test revealed highly statistical significant differences between them (P < 0.00). The study establishes a strong cytogentic data, which can contribute to accurate identification of the mosquito An. arabiensis and to planning human malaria vector control programs in Kassala State, eastern Sudan.

Chromosomal evolution in Rattini (Muridae, Rodentia)

The Rattini (Muridae, Murinae) includes the biologically important model species Rattus norvegicus (RNO) and represents a group of rodents that are of clinical, agricultural and epidemiological importance. We present a comparative molecular cytogenetic investigation of ten Rattini species representative of the genera Maxomys, Leopoldamys, Niviventer, Berylmys, Bandicota and Rattus using chromosome banding, cross-species painting (Zoo-fluorescent in situ hybridization or FISH) and BAC-FISH mapping. Our results show that these taxa are characterised by slow to moderate rates of chromosome evolution that contrasts with the extensive chromosome restructuring identified in most other murid rodents, particularly the mouse lineage. This extends to genomic features such as NOR location (for example, NORs on RNO 3 are present on the corresponding chromosomes in all species except Bandicota savilei and Niviventer fulvescens, and the NORs on RNO 10 are conserved in all Rattini with the exception of Rattus). The satellite I DNA family detected and characterised herein appears to be taxon (Rattus) specific, and of recent origin (consistent with a feedback model of satellite evolution). BAC-mapping using clones that span regions responsible for the morphological variability exhibited by RNO 1, 12 and 13 (acrocentric/submetacentric) and their orthologues in Rattus species, demonstrated that the differences are most likely due to pericentric inversions as exemplified by data on Rattus tanezumi. Chromosomal characters detected using R. norvegicus and Maxomys surifer whole chromosome painting probes were mapped to a consensus sequence-based phylogenetic tree thus allowing an objective assessment of ancestral states for the reconstruction of the putative Rattini ancestral karyotype. This is thought to have comprised 46 chromosomes that, with the exception of a single pair of metacentric autosomes, were acrocentric in morphology.

A Novel Karyotype in a South Indian Tettigonid. (Subfam: Listroscelinae-Orthoptera).

1) During a chromosomal survey of the tettigonids an unusual specimen No. 207 (in our list of specimens) was discovered which is tentatively placed under the genus Euhexacentrus of the subfam : Listroscelinae. 2) Euhexacentrus sp. (specimen No. 207) is unusual among the tettigonids as its karyotype has the lowest chromosome number of 2n=9 (8A+X) with 4 pairs of metacentric autosomes and a smaller acrocentric X chromosome. 3) This karyotype is compared with the karyotype of E. annulicornis, whose chromosome number is 12 (10A+XY) and are all metacentric. 4) The karyotype details of all the known species of the subfam : Listroscelinae are presented for comparison along with the present Euhexacentrus sp. 5) The probable evolution of the present karyotype is discussed.

Sambar deer (Cervus unicolor) x red deer (C. elaphus) interspecies hybrids.

The artificial insemination of 400 red deer hinds with sambar deer semen resulted in 31 pregnancies at day 40 (24 at day 100) and the birth of four calves. Only one female calf was born alive. The artificial insemination of 10 sambar deer hinds with red deer semen resulted in five pregnancies at day 40, of which none went to term. Gel electrophoresis of three blood proteins confirmed the live calf as the first documented sambar deer x red deer hydrid. G-banded karyotypes were consistent with the calf (2n = 62; six unpaired and one paired metacentric autosomes) being the offspring of a red deer dam (2n = 68; single pair of metacentric autosomes) and a sambar deer sire (2n = 56; seven pairs of metacentric autosomes).

Conservation of a 31-bp bovine subrepeat in centromeric satellite DNA monomers of Cervus elaphus and other cervid species.

A centromeric satellite DNA clone was isolated from the genome of the European red deer (Cervus elaphus hippelaphus) and designated Ce-Pst1. This clone was localized to the centromeric region of all red deer chromosomes with the exception of a single pair of metacentric autosomes and the Y chromosome. DNA sequence analysis of the 806-bp Ce-Pst1 clone showed 73.0-78.9% sequence homology to four previously isolated cervid centromeric satellite DNA clones, suggesting that the Ce-Pst1 clone is yet another member of the major cervid centromeric satellite DNA family. Using a DNA sequence comparison system, internal 31-bp tandem subrepeats were found in the Ce-Pst1 clone as well as in the other previously reported cervid centromeric satellite DNA monomer sequences. A 31-bp consensus sequence was constructed for each cervid monomer clone and shown to be highly homologous to the 31-bp subrepeat consensus sequence found in bovine 1.715 centromeric satellite DNA. The identification of internal subrepeats in the satellite monomers studied could suggest that amplification of an ancestral 31-bp DNA sequence may have contributed to the genesis of major cervid centromeric satellite DNA. The homology between the 31-bp subrepeats found in cervid and bovid centromeric satellite DNAs substantiates the theory that amplification of this 31-bp DNA sequence may have occurred before the evolutionary separation of these two families 20-25 million years ago.

Chromosomal polymorphism and speciation in the genusEunemobius (Orthoptera: Grylloidea)

Karyotypes are described for the three species of ground crickets belonging to the North American genusEunemobius. All species possess three pairs of metacentric autosomes and a submetacentric X-chromosome. The sex-determination mechanism is XX-XO with 2n=7 in males and 2n=8 in females. There is no evidence that chromosomal rearrangements have been involved in speciation in the group.

Karyotype study of 5 species of Costa Rican snakes of the colubrid family

The karyotypes of five species of colubrid snakes from Costa Rica are as follows: Imantodes cenchoa and Drymobius margaritiferus have a diploid number of 36, with 16 macro- and 20 microchromosomes. The fourth pair is heteromorphic in females of I. cenchoa, with a metacentric Z and a submetacentric W chromosomes. Karyotypes of Erythrolampius bizonus and Leimadophis epinephalus have 28 chromosomes, without a clearcut separation between macro- and microchromosomes. In the case of E. bizomus, the fourth pair contains the sex chromosomes Z and W, both are submetacentric, but the W is smaller. Xenedon rabdocephalus has a diploid number of 34 chromosomes (22 macro- and 12 microchromosomes); pair 3 is heteromorphic in females, with a submetacentric Z and a smaller metacentric W. The karyotype of X. rabdocephalus may be derived from a primitive karyotype by means of reduction in the number of microchromosomes and centric fissions of two pairs of metacentric autosomes.

Chromosomy kilku gatunków mroczkowatych. II. Ewolucyjne zależności w obrębie Plecotini

Differential staining revealed a total accordance of banding pattern for all the chromosomes of Plecotus auritus (Linnaeus, 1758) and Barbastella barbastellus (Schreber, 1774). The kariotypes of these two species are identical and consist of 32 chromosomes, including 10 pairs of metacentric autosomes, 5 pairs of telocentric autosomes, a submetacentric X-chromosome, and a small acrocentric y-chromosome.

A cytogenetical study of Glossina fuscipes fuscipes including a comparison of the polytene chromosome maps with those of Glossina austeni (Diptera, Glossinidae)

The male meiotic sequence is described for the tsetse fly Glossina fuscipes fuscipes together with the polytene chromosome maps and all principal cytological markers. The diploid chromosome number is 2n=6 and includes a pair of large submetacentric autosomes (L1), a shorter pair of metacentric autosomes (L2), and an X and Y which constitute a heteromorphic pair. Male meiosis is normally achiasmate although evidence is presented which suggests that chiasmata do form in about 1% of males. A detailed comparison between the polytene chromosomes of this species and Glossina austeni indicates that although they must have had a common ancestor, G. austeni is genetically more closely related to morsitans group tsetses.

Karyotypes of some interspecific hybrids of Pitymys (Mammalia, Rodentia)

The Robertsonian polymorphism ofPitymys subterraneus involves only 1 pair of metacentric autosomes. The crosses of forms with 52, 53 and 54 chromosomes do not show any differences in their reproductive rate. So a single autosome trivalent does not affect the fecondity. Many hybrids have been obtained betweenP. subterraneus (2N=52 or 54) andP. multiplex (2N=48) with 50 or 51 chromosomes, respectively. Even with a heterogenous karyotype they are not entirely sterile. 2 progeny were produced from back-crosses. The 2 parental species seem to result from recent speciation. Only fecondation or embryogenesis occurs in crossingP. duodecimcostatus withP. subterraneus orP. multiplex. The chromosome complement of 1 hybrid embryo ofP. duodecimcostatus (2N=62)×P. multiplex (2N=48) has been studied showing 55 chromosomes.P. duodecimcostatus appears to belong to a more distant evolutionary group.

Number and morphology of chromosomes in three geographical populations of Ascidiella aspersa (Ascidiacea)

In contrast with some previous reports, we have found the same number of chromosomes (n=9, 2n=18) for Ascidiella aspersaMuller from the Gulf of Naples, the west coast of Scotland and the Lagoon of Venice. It follows that the hypothesis, that different geographical populations of A. aspersa might possess different chromosome numbers, is no longer tenable. The karyogram of A. aspersa shows 9 pairs of metacentric autosomes. The oocyte bivalents show chiasmata and are characterized by the faintness with which they are stained.

CHROMOSOMAL POLYMORPHISM INPISSODES WEEVILS: FURTHER ON INCOMPATIBILITY IN P.TERMINALS

The North American Pissodes terminalis exhibits dual sexual dichotomy of its karyotype. Whereas females are invariably homozygous both for the sex chromosomes and a pair of metacentric autosomes (XC/XC), all males are double heterozygotes (XC/Ycc), one C being replaced by its corresponding twin acrocentrics. Consequently females produce only X/C eggs but, since meiotic orientation of the XY II and the Ccc III is random, males should produce four types of spermatozoa in equal proportions. If so, to render the dual dichotomy permanent, effective fertilization must perforce be solely by XC and Ycc sperms.Hybrids have been obtained between different taxa that are monomorphic either for two C-metacentrics or for their equivalent twin c-acrocentrics. When the cs in hybrid males are of paternal origin, the semi-incompatibility system (SIS), as seen in terminalis, is immediately synthesized and thereafter faithfully perpetuated. When, however, they are of maternal origin, free recombination ensues both in the F2and backcrosses. An identical alternate scheme of inheritance is displayed when terminalis is one or the other parent. Egg viability, sex ratio, late mortality, and family size in SIS hybrids show no significant deviation relative to those of monomorphic species or non-SIS hybrids. It is therefore concluded that the autosomal heterozygosity of SIS males is a consequence not of a balanced lethal mechanism but of selective fertilization. This system can be formally ascribed to translocation of a factor from one of the twin acrocentrics to the Y (Xcc: Ycc → Xcc/Y+c−c); thereby these two mutually compensating chromosomes became permanently linked in heredity and concomitantly excluded from females.The synthesis of the SIS in intra-complex hybrids demonstrates that the seeming random recombination in c-acrocentric species is illusory. They likewise possess a built-in SIS, one that is only exposed after crossing to C-metacentric females. Significantly, other species complexes in the genus also have an innate SIS, but they fail to conceal it because in males their c/c−II is readily visible. Thus it follows that the mutation did not originate in terminalis, a species of obvious recent origin.The absence of the system from C-metacentric taxa, we attribute to their obvious Robertsonian origin from c-acrocentric SIS species by centric fusion of nonhomologues. Such a fusion, by arising in the female, exempts the male c−from direct participation and, following introduction of the newly formed C chromosome into males(v. terminalis), merely await loss of the plus factor from the Y+to ensure the free recombination currently seen in C:C taxa, for Yc−c gametes should thereby be totally incapacitated.

Robertsonian Polymorphism in the Cotton Rat, Sigmodon fulviventer

Karyotypes of 28 fulvous-bellied cotton rats, Sigmodon fulviventer, from Arizona and New Mexico were analyzed. Intrapopulational variation in diploid numbers of 30, 29, and 28 was found. This polymorphism is ascribed to Robertsonian changes: centric fusion or fission involving two pairs of acrocentric autosomes or one pair of metacentric autosomes, respectively. Possible mechanisms are discussed for the origin of this polymorphism and its evolutionary significance. The relatively high frequency of each diploid type is contrasted with the condition in certain other species of mammals. Tentative remarks concerning chromosomal relationships among four kinds of Sigmodon are presented.

Chromosomes of the horse, the donkey, and the mule.

1. The diploid chromosome number forEquus caballus is 64, that forEquus asinus is 62, and that for the mule, 63. 2. The chromosome complements ofE. caballus andE. asinus are completely different morphologically.E. caballus has 19 pairs of metacentric autosomes and 18 pairs of acrocentrics, whileE. asinus has 19 pairs of metacentric autosomes and 11 pairs of acrocentrics. The morphology of the sex chromosomes is also dissimilar between the species. 3. While the disparity between parental chromosomes satisfactorily accounts for sterility in male hybrids, it does not explain the occasional fertile female able to produce several offspring with noE. asinus traits. Apparently morphological disparity between parental chromosomes is only a small part of the relatively complex matter of female gametogenesis.