Metacentric Chromosomes Research Articles

Two species of Polycelis (Platyhelminthes, Tricladida, Planariidae) newly recorded for the Qinling Mountains and the Loess Plateau in China, with a comparative discussion on their karyotypes

The paper details new geographic records of two species of the genus Polycelis Ehrenberg,1831 (Platyhelminthes, Tricladida, Planariidae) for the Qinling Mountains and the Loess Plateau in China and provides redescriptions of these species based on an integrative taxonomic study involving morphology, karyology, and histology. This new information considerably expands our knowledge on these species, for which until now only limited data was available. The species Polycelis asiatica Selinova, 1985 is characterized by the following features: 63–80 eyes; sperm ducts that exhibit an intrabulbar knee-shaped bend towards the ventral surface before opening separately and symmetrically into the antero-dorsal portion of a large seminal vesicle; the latter is ventrally displaced, thus creating a narrow ventral lip on the penis papilla; dorsal wall of the seminal vesicle is provided with several well-developed folds; more or less bulbous penis papilla protrudes from the dorsal wall of the male atrium and is provided with a slender and flexible tip; chromosome complement diploid with 30 metacentric chromosomes, 8 submetacentric chromosomes, and 2 subtelocentric chromosomes. The species Polycelis eudendrocoeloides (Zabusova, 1929) is characterized by: 49–80 eyes; highly reduced and blunt penis, provided with a kind of flagellum that projects into the seminal vesicle; a relatively thick coat of circular and longitudinal muscles around the entire male atrium; generally, a very large intrabulbar seminal vesicle, extending from near the ventral body surface to occupy the major part of both the penis bulb and the dorso-ventral space of the body; diploid chromosome complement consisting of 36 metacentric chromosomes.

Karyotypic description and comparison of Litoria (L.) paraewingi (Watson et al., 1971), L.ewingii (Duméril et Bibron, 1841) and L.jervisiensis (Duméril et Bibron, 1841) (Amphibia, Anura).

The karyotype of Litoria (L.) paraewingi (Watson et al., 1971) (Big River State Forest, Victoria) is described here for the first time. It is prepared following tissue culture of toe clipping macerates, cryopreservation, reculture and conventional 4',6-diamidino-2-phenylindole (DAPI) staining. The L.paraewingi karyotype is then compared to similarly processed IUCN (International Union for the Conservation of Nature) least concern members L.ewingii (Duméril et Bibron, 1841) (southern Victoria) and L.jervisiensis (Duméril et Bibron, 1841) (Myall Lakes National Park, New South Wales), all members of the same L.ewingii complex/group. The L.paraewingi diploid number is 2n = 26, the same as for the other two species. Litoriaparaewingi chromosomes 1, 2, 6 and 7 are submetacentric, chromosomes 3 and 5 are subtelocentric and the remainder are metacentric. No secondary constriction or putative nucleolus organiser region (NOR) was readily identifiable following conventional DAPI staining in any scored L.paraewingi metaphase spread. Conversely, a putative NOR was readily identifiable on the long arm of chromosome 1 in all examined metaphase spreads for the other two species. The karyotypes of L.ewingii and L.jervisiensis here further differ from L.paraewingi with chromosome 1 being metacentric and chromosomes 8 and 10 being submetacentric for both former species. The L.jervisiensis karyotype differs from those of L.ewingii and L.paraewingi by DAPI staining with: (i) apparent relative length inversion of subtelocentric chromosome 3 and metacentric chromosome 4 and (ii) chromosome 6 being metacentric rather than submetacentric. All three species have a highly conserved chromosome morphology with respect to chromosomes 2, 5, 7, 9, 11, 12 and 13. The greatest gross morphological difference karyotypically is observed between L.paraewingi and L.jervisiensis. These karyotype data support the previous phylogenetic separation of these three species based upon genetic compatibility and behavioural, biochemical and molecular genetic analyses.

Karyotype diversity and genome size in the Cyphomandra clade of Solanum L. (Solanaceae)

Abstract The Cyphomandra clade, a distinct group within the Solanum L. genus, is characterized by remarkable traits, including large chromosomes and big genome sizes. We aimed to investigate whether these features are conserved within the Cyphomandra clade and how they differentiate this group from other Solanum species. We elaborated karyotypes based on CMA/DAPI banding and rDNA fluorescence in situ hybridization (FISH) and estimated the genome size from 12 species, eight belonging to Cyphomandra and four from related clades. All species showed metacentric or submetacentric chromosomes and symmetrical karyotypes, with 2n = 24, except S. mammosum L. (2n = 22). CMA/DAPI banding in combination with rDNA FISH revealed three distinct patterns of heterochromatin distribution (number and position of bands, all CMA+). Most species showed one pair of 35S and 5S rDNA on different chromosomes, except S. mammosum (one of the two pairs was observed in the same chromosome). Notable, the Cyphomandra clade species showed larger chromosomes and genome sizes than other species of Solanum, corroborating that these karyotype attributes are valuable to characterize the clade. The number of CMA/DAPI bands and rDNA sites does not justify the differences in the genome size. Therefore, the accumulation and dispersion of other repetitive sequences, like transposable elements, may be associated with the karyotype changes.

Robertsonian Translocation between Human Chromosomes 21 and 22, Inherited across Three Generations, without Any Phenotypic Effect

Chromosomal translocations can result in phenotypic effects of varying severity, depending on the position of the breakpoints and the rearrangement of genes within the interphase nucleus of the translocated chromosome regions. Balanced translocations are often asymptomatic phenotypically and are typically detected due to a decrease in fertility resulting from issues during meiosis. Robertsonian translocations are among the most common chromosomal abnormalities, often asymptomatic, and can persist in the population as a normal polymorphism. We serendipitously discovered a Robertsonian translocation between chromosome 21 and chromosome 22, which is inherited across three generations without any phenotypic effect, notably only in females. In situ hybridization with alpha-satellite DNAs revealed the presence of both centromeric sequences in the translocated chromosome. The reciprocal translocation resulted in a partial deletion of the short arm of both chromosomes 21, and 22, with the ribosomal RNA genes remaining present in the middle part of the new metacentric chromosome. The rearrangement did not cause alterations to the long arm. The spread of an asymptomatic heterozygous chromosomal polymorphism in a population can lead to mating between heterozygous individuals, potentially resulting in offspring with a homozygous chromosomal configuration for the anomaly they carry. This new karyotype may not produce phenotypic effects in the individual who presents it. The frequency of karyotypes with chromosomal rearrangements in asymptomatic heterozygous form in human populations is likely underestimated, and molecular karyotype by array Comparative Genomic Hybridization (array-CGH) analysis does not allow for the identification of this type of chromosomal anomaly, making classical cytogenetic analysis the preferred method for obtaining clear results on a karyotype carrying a balanced rearrangement.

Molecular cytogenetic characterization of 9 populations of four species in the genus Polygonatum (Asparagaceae).

To characterize the chromosomes of the four species of Polygonatum Miller, 1754, used in traditional Chinese medicine, P.cyrtonema Hua, 1892, P.kingianum Collett et Hemsley, 1890, P.odoratum (Miller, 1768) Druce, 1906, and P.sibiricum Redouté, 1811, and have an insight into the karyotype variation of the genus Polygonatum, fluorescence in situ hybridization (FISH) with 5S and 45S rDNA oligonucleotide probes was applied to analyze the karyotypes of 9 populations of the four species. Detailed molecular cytogenetic karyotypes of the 9 populations were established for the first time using the dataset of chromosome measurements and FISH signals of 5S and 45S rDNA. Four karyotype asymmetry indices, CVCI, CVCL, MCA and Stebbins' category, were measured to elucidate the asymmetry of the karyotypes and karyological relationships among species. Comparison of their karyotypes revealed distinct variations in the karyotypic parameters and rDNA patterns among and within species. The basic chromosome numbers detected were x = 9, 11 and 13 for P.cyrtonema, x = 15 for P.kingianum, x = 10 and 11 for P.odoratum, and x = 12 for P.sibiricum. The original basic chromosome numbers of the four species were inferred on the basis of the data of this study and previous reports. All the 9 karyotypes were of moderate asymmetry and composed of metacentric, submetacentric and subtelocentric chromosomes or consisted of two of these types of chromosomes. Seven populations have one locus of 5S rDNA and two loci of 45S rDNA, and two populations added one 5S or 45S locus. The karyological relationships among the four species revealed by comparison of rDNA patterns and PCoA based on x, 2n, TCL, CVCI, MCA and CVCL were basically accordant with the phylogenetic relationships revealed by molecular phylogenetic studies. The mechanisms of both intra- and inter-specific dysploidy in Polygonatum were discussed based on the data of this study and literature.

A working model for the formation of Robertsonian chromosomes.

Robertsonian chromosomes form by fusion of two chromosomes that have centromeres located near their ends, known as acrocentric or telocentric chromosomes. This fusion creates a new metacentric chromosome and is a major mechanism of karyotype evolution and speciation. Robertsonian chromosomes are common in nature and were first described in grasshoppers by the zoologist W. R. B. Robertson more than 100 years ago. They have since been observed in many species, including catfish, sheep, butterflies, bats, bovids, rodents and humans, and are the most common chromosomal change in mammals. Robertsonian translocations are particularly rampant in the house mouse, Mus musculus domesticus, where they exhibit meiotic drive and create reproductive isolation. Recent progress has been made in understanding how Robertsonian chromosomes form in the human genome, highlighting some of the fundamental principles of how and why these types of fusion events occur so frequently. Consequences of these fusions include infertility and Down's syndrome. In this Hypothesis, I postulate that the conditions that allow these fusions to form are threefold: (1) sequence homology on non-homologous chromosomes, often in the form of repetitive DNA; (2) recombination initiation during meiosis; and (3) physical proximity of the homologous sequences in three-dimensional space. This Hypothesis highlights the latest progress in understanding human Robertsonian translocations within the context of the broader literature on Robertsonian chromosomes.

Multiple Genomic Landscapes of Recombination and Genomic Divergence in Wild Populations of House Mice-The Role of Chromosomal Fusions and Prdm9.

Chromosomal fusions represent one of the most common types of chromosomal rearrangements found in nature. Yet, their role in shaping the genomic landscape of recombination and hence genome evolution remains largely unexplored. Here, we take advantage of wild mice populations with chromosomal fusions to evaluate the effect of this type of structural variant on genomic landscapes of recombination and divergence. To this aim, we combined cytological analysis of meiotic crossovers in primary spermatocytes with inferred analysis of recombination rates based on linkage disequilibrium using single nucleotide polymorphisms. Our results suggest the presence of a combined effect of Robertsonian fusions and Prdm9 allelic background, a gene involved in the formation of meiotic double strand breaks and postzygotic reproductive isolation, in reshaping genomic landscapes of recombination. We detected a chromosomal redistribution of meiotic recombination toward telomeric regions in metacentric chromosomes in mice with Robertsonian fusions when compared to nonfused mice. This repatterning was accompanied by increased levels of crossover interference and reduced levels of estimated recombination rates between populations, together with high levels of genomic divergence. Interestingly, we detected that Prdm9 allelic background was a major determinant of recombination rates at the population level, whereas Robertsonian fusions showed limited effects, restricted to centromeric regions of fused chromosomes. Altogether, our results provide new insights into the effect of Robertsonian fusions and Prdm9 background on meiotic recombination.

Repetitive DNA Mapping in Five Genera of Tree Frogs (Amphibia: Anura) from the Atlantic Forest: New Highlights on Genomic Organization in Hylidae

Introduction: The tribes Cophomantini, Scinaxini, and Dendropsophini are anurans that belong to Hylidae, with wide distribution in tropical and subtropical regions around the world. The taxonomy and systematics of this family remain in a state of ongoing revision. Previous cytogenetic analyses of genera Boana, Bokermannohyla, Ololygon, Scinax, and Dendropsophus described some karyotypic characters such as conventional staining, C-banding and NORs, and FISH with specific probes. Methods: This study describes for the first time the karyotypes of four species: Bokermannohyla ibitipoca, Ololygon luizotavioi, Dendropsophus bipunctatus, and Dendropsophus ruschii. Furthermore, we map CA(15) and CAT(10) microsatellite sites for the aforementioned species and six more species from the same genera for insight into the chromosomal evolution within the subfamily Hyalinae. Results: B. ibitipoca and O. luizotavioi had 2n = 24 and karyotypic formulas 18m + 4sm + 2st and 8m + 12sm + 4st, while D. bipunctatus and D. ruschii showed 2n = 30 and karyotypic formulas 12m + 12sm + 4st + 2t and 10m + 10sm + 6st + 4t, respectively. The diploid numbers and karyotypic formulas revealed here follow the previously reported trend for Hylidae, except B. ibitipoca has a particularity of eight metacentric chromosomes, more than what is commonly found in species of this genus. The microsatellites probes CA(15) and CAT(10) had markings accumulated in blocks in the centromeric, pericentromeric, and terminal regions that were more specific for some species, as well as markings scattered along the chromosomes. We present a comprehensive review table of current data on cytogenetics of these genera. Conclusion: Our findings showed that the karyotypes of the hylids studied here majority fit the postulated conserved diploid number (2n = 24) and morphological chromosome patterns, while the mapping of the microsatellites enabled us to detect differences between species that share similar chromosomal morphologies.

Karyotype profile of holarrhena antidysenterica (Roxb. Ex fleming) wall

The karyomorphological features of Holarrhena antidysenterica (Roxb. ex Fleming) Wall. through the application of differential staining techniques (using orcein, CMA, and DAPI) were studied. After applying orcein staining, the interphase nuclei of this species exhibited a ‘simple chromocenter type’ with numerous small heterochromatin blocks and the prophase chromosomes were ‘interstitial type’. The karyotype analysis revealed that this species possesses diploid chromosome number of 2n = 22, with all metacentric chromosomes. The total length of the chromosome complement in the diploid set was 29.91 μm. A total of four CMA-positive bands were observed in this species whereas seven bands were found after DAPI-staining. Heteromorphicity was observed in the DAPI stained metaphase stage indicating the probable occurrences of chromosomal aberrations such as deletion and inversion. The karyotype profile of H. antidysenterica obtained from orcein and fluorescent banding was determined for the first time in Bangladesh. Bangladesh J. Bot. 52(4): 1085-1089, 2023 (December)

Karyotypes and Physical Mapping of Ribosomal DNA with Oligo-Probes in Eranthis sect. Eranthis (Ranunculaceae).

A comparative karyotype analysis of four species of yellow-flowered Eranthis sect. Eranthis, i.e., E. bulgarica, E. cilicica, E. hyemalis, and E. longistipitata from different areas, has been carried out for the first time. All the studied specimens had somatic chromosome number 2n = 16 with basic chromosome number x = 8. Karyotypes of the investigated plants included five pairs of metacentric chromosomes and three pairs of submetacentric/subtelocentric chromosomes. The chromosome sets of the investigated species differ mainly in the ratio of submetacentric/subtelocentric chromosomes, their relative lengths, and arm ratios. A new oligonucleotide probe was developed and tested to detect 45S rDNA clusters. Using this probe and an oligonucleotide probe to 5S rDNA, 45S and 5S rDNA clusters were localized for the first time on chromosomes of E. cilicica, E. hyemalis, and E. longistipitata. Major 45S rDNA clusters were identified on satellite chromosomes in all the species; in E. cilicica, minor clusters were also identified in the terminal regions of one metacentric chromosome pair. The number and distribution of 5S rDNA clusters is more specific. In E. cilicica, two major clusters were identified in the pericentromeric region of a pair of metacentric chromosomes. Two major clusters in the pericentromeric region of a pair of submetacentric chromosomes and two major clusters in the interstitial region of a pair of metacentric chromosomes were observed in E. longistipitata. E. hyemalis has many clusters of different sizes, localized mainly in the pericentromeric regions. Summarizing new data on the karyotype structure of E. sect. Eranthis and previously obtained data on E. sect. Shibateranthis allowed conclusions to be formed about the clear interspecific karyological differences of the genus Eranthis.

Repositioning of centromere-associated repeats during karyotype evolution in Oryzias fishes.

The karyotype, which is the number and shape of chromosomes, is a fundamental characteristic of all eukaryotes. Karyotypic changes play an important role in many aspects of evolutionary processes, including speciation. In organisms with monocentric chromosomes, it was previously thought that chromosome number changes were mainly caused by centric fusions and fissions, whereas chromosome shape changes, that is, changes in arm numbers, were mainly due to pericentric inversions. However, recent genomic and cytogenetic studies have revealed examples of alternative cases, such as tandem fusions and centromere repositioning, found in the karyotypic changes within and between species. Here, we employed comparative genomic approaches to investigate whether centromere repositioning occurred during karyotype evolution in medaka fishes. In the medaka family (Adrianichthyidae), the three phylogenetic groups differed substantially in their karyotypes. The Oryzias latipes species group has larger numbers of chromosome arms than the other groups, with most chromosomes being metacentric. The O. javanicus species group has similar numbers of chromosomes to the O. latipes species group, but smaller arm numbers, with most chromosomes being acrocentric. The O. celebensis species group has fewer chromosomes than the other two groups and several large metacentric chromosomes that were likely formed by chromosomal fusions. By comparing the genome assemblies of O. latipes, O. javanicus, and O. celebensis, we found that repositioning of centromere-associated repeats might be more common than simple pericentric inversion. Our results demonstrated that centromere repositioning may play a more important role in karyotype evolution than previously appreciated.

Cytogenetic characteristics of invasive Corbicula fluminalis (Bivalvia: Cyrenidae) of the Northern Dvina River basin

The ploidy between invasive Corbicula lineages can be di-, tri-, and tetraploid. Currently, some invasive populations of this genus remain unaffected by cytogenetic studies. In this study, we determined the chromosome set of invasive C. fluminalis (O. F. Muller, 1774) from Northern European Russia. According to our results, the chromosome set C. fluminalis consists of 54 chromosomes, which can be divided into 18 groups of 3 phenotypically identical chromosomes. Among them we can distinguish 3 metacentric chromosomes, 15 submetacentric chromosomes and 36 subtelo-acrocentric chromosomes.

Karyotype and genome size variation in Delphinium subg. Anthriscifolium (Ranunculaceae).

Five taxa of Delphiniumsubg.Anthriscifolium have been karyologically studied through chromosome counting, chromosomal measurement, and karyotype symmetry. Each taxon that we investigated has a basic chromosome number of x = 8, D.anthriscifoliumvar.savatieri, D.anthriscifoliumvar.majus, D.ecalcaratum, and D.callichromum were diploid with 2n = 16, while D.anthriscifoliumvar.anthriscifolium was tetraploid with 2n = 32. Monoploid chromosome sets of the investigated diploid taxa contained 1 metacentric chromosome, 3 submetacentric chromosomes, and 4 subtelocentric chromosomes. Higher interchromosomal asymmetry (CVCL) was present in D.ecalcaratum and D.callichromum than in other taxa. The highest levels of intrachromosomal asymmetry (MCA) and heterogeneity in centromere position (CVCI) were found in D.anthriscifoliumvar.majus. Diploid and tetraploid genome sizes varied by 3.02-3.92 pg and 6.04-6.60 pg, respectively. Karyotype and genome size of D.anthriscifoliumvar.savatieri, D.anthriscifoliumvar.majus, D.callichromum, and D.ecalcaratum were reported for the first time. Finally, based on cytological and morphological data, the classification of Delphiniumanthriscifolium was revised.

New chromosomal data, karyotype asymmetry and polyploid variations of some Gundelia (Asteraceae) species from Turkey

The genus Gundelia is currently represented with 18 species, of which 16 are in Turkey. In genus Gundelia, the chromosomal data were reported from 12 species. In the present study, it is aimed to eliminate the deficiencies in the knowledge about chromosomal data of Gundelia species. In Genus Gundelia, only a single chromosome number had been detected as 2n=18 so far. The chromosome numbers of four species were reported here for the first time: G. armeniaca, G. cappadocica, G. siirtica, and G. tehranica. In addition, the polyploidy in the genus was rare and G. anatolica was identified as the first polyploid species. All karyotypes except G. tehranica were symmetrical, consisting of metacentric and submetacentric chromosomes. Secondary constrictions were observed in the distal regions of the long arms of the longest metacentric and submetacentric chromosomes. Thus, the chromosomal data of all Turkish Gundelia species were completed. In conclusion, the present study presented new data into the karyological records relating the karyotype evolution and interspecific relations of genus Gundelia.

Cytogenetic Study of Five Varieties of Callisia repens (Jacq.) L. (Commelinaceae) from Laos

Cytogenetical studies were carried out on five varieties of Callisia repens, i.e., turtle vine, green, pink lady, gold, and Bianca. The morphological characteristics of all five varieties differed in leaf shape and color of the plant. All five varieties have the same chromosome number, 2n = 12, and the fundamental number (NF) = 24. The number of metacentric (m), submetacentric (sm), and subtelocentric (st) chromosomes was related to the discrepancies between the various karyotypes that were found. The formula for each of the karyotypes was 2m + 2sm + 8st (turtle vine), 2m + 10st (green), 8m + 4st 14 (pink lady), 2m + 4sm + 6st (gold), and 2m + 2sm + 8st (Bianca). Therefore, all five strains had asymmetrical karyotypes. The chromosome number of C. repens has been reported previously, but this is the first report of karyotype variation among the varieties. Furthermore, principal component analysis (PCA) of the karyotype formula was able to distinguish C. repens ‘pink lady’, C. repens ‘green’, and C. repens ‘gold’, but it was unable to differentiate between C. repens ‘Bianca’ and C. repens ‘turtle vine’. Additionally, PCA conducted on the centromeric index (CI) and the leaf colors of the five varieties of C. repens successfully separated all of them. Therefore, the prominent morphological traits and karyotype information of the five varieties of C. repens from Laos can be used to distinguish between them.

Polyploidy in Muscari neglectum (Asparagaceae) by analysis of karyotype and Giemsa C-banding patterns

This study provides new karyological information on polyploid cytotypes of Muscari neglectum. Classical cytogenetic with the Feulgen technique and banding with Giemsa was used. Pentaploid, hexaploid and heptaploid levels of ploidy are here reported. The complement of the rare heptaploid cytotype consisted of 2n = 7x = 63: 49 m + 14sm chromosomes. Two heptaploid specimens with chromosome numbers 60 and 62 were also found. Karyotypes were symmetrical, with metacentric chromosomes more numerous than submetacentric. The morphometric parameters MCA and CVCL were used for the evaluation of karyotype asymmetry. For the first time, a detailed study using Giemsa C-banding is reported. The C-banding patterns included centromeric and terminal bands. In the cytotype with 62 chromosomes, the banding patterns identified the presence of a chromosome with terminal band in both arms. To explain the origin of this karyotype, we suggest that fusion occurred between a group IV chromosome and a group V chromosome. The relationship between the polyploid cytotypes of M. neglectum is discussed.

Multiple Chromosome Fissions, Including That of the X Chromosome, in Aulacocyclus tricuspis Kaup (Coleoptera, Passalidae) from New Caledonia: Characterization of a Rare but Recurrent Pathway of Chromosome Evolution in Animals.

The male karyotype of Aulacocyclus tricuspis Kaup 1868 (Coleoptera, Scarabaeoidea, Passalidae, Aulacocyclinae) from New Caledonia contains an exceptionally high number of chromosomes, almost all of which are acrocentric (53,X1X2Y). Unlike the karyotypes of other species of the pantropical family Passalidae, which are principally composed of metacentric chromosomes, this karyotype is derived by fissions involving almost all the autosomes after breakage in their centromere region. This presupposes the duplication of the centromeres. More surprising is the X chromosome fragmentation. The rarity of X chromosome fission during evolution may be explained by the deleterious effects of alterations to the mechanisms of gene dosage compensation (resulting from the over-expression of the unique X chromosome in male insects). Herein, we propose that its occurrence and persistence were facilitated by (1) the presence of amplified heterochromatin in the X chromosome of Passalidae ancestor, and (2) the capacity of heterochromatin to modulate the regulation of gene expression. In A. tricuspis, we suggest that the portion containing the X proper genes and either a gene-free heterochromatin fragment or a fragment containing a few genes insulated from the peculiar regulation of the X by surrounding heterochromatin were separated by fission. Finally, we show that similar karyotypes with multiple acrocentric autosomes and unusual sex chromosomes rarely occur in species of Coleoptera belonging to the families Vesperidae, Tenebrionidae, and Chrysomelidae. Unlike classical Robertsonian evolution by centric fusion, this pathway of chromosome evolution involving the centric fission of autosomes has rarely been documented in animals.

Morphological Differentiation and Karyotypic Studies of the African Common Toad Sclerophrys (Bufo) Regularis (Reuss, 1833)

The study analyzed the morphological differentiation and karyotype among populations of the common toad, Sclerophrys (Bufo) regularis from six Local Government Areas in Ondo state. Variations in fifteen morphometric and qualitative characters in one hundred and seventy-one animals from six population samples were analyzed using univariate and multivariate statistics. Descriptives of sexes and correlation between morphological characters was also analyzed. Female toads had larger mean values of most of the morphological characters studied with weight contributing the largest variance. The chromosomes of twenty-four specimens of the toad were also studied using standard bone marrow smear techniques. A chromosome complement of 2n=20 was observed for this species. The chromosomes consists of nine pairs of metacentric and one pair of submetacentric chromosomes. The chromosomes based on centromeric position could be grouped into two - metacentric and submetacentric - and based on size, into three metacentric chromosomes; 1-4 which were large, metacentric chromosomes; 5-6 medium sized metacentric chromosomes, while 7-9 were small sized, and the last pair (10), submetacentric chromosomes were small. The fundamental number of this species is 40 and with no sex chromosomes or satellites reported, while bi-armed chromosomes were observed. Findings also showed that female individuals of the species weighed more than the male.

Karyotype comparison and characterization of two cauliflower cultivars from Bangladesh

Two cauliflower cultivars were karyotyped for correct characterization after orcein staining. Both cultivars have a simple chromocenter type of interphase nuclei and a gradient type of prophase chromosomes, indicating that they descended from a common ancestor. In addition, both strains were found to have 2n=18 chromosomes with an almost identical range of chromosome lengths. In terms of overall length, the white snow cultivar is almost 7 m shorter than the fresh market cultivar, indicating the presence of chromatin length diversification between specimens. In none of the cases was there a noticeable gradual decrease in chromosome length. The metacentric and submetacentric chromosomes were observed in both samples examined. Apart from other karyotypic features, TF, Syi and AsK % indicate the moderately symmetrical nature of the karyotype. As a result, the two cultivars of cauliflower were moderately primitive in nature. The collection of this karyotypic data will aid in the authentic characterization of the two cauliflower cultivars, which is essential information for the breeding program.
 Jahangirnagar University J. Biol. Sci. 11(1 & 2): 21-30, 2022 (June & December)

Analysis in Proceratophrys boiei genome illuminates the satellite DNA content in a frog from the Brazilian Atlantic forest.

Satellite DNAs (satDNAs) are one of the most abundant elements in genomes. Characterized as tandemly organized sequences that can be amplified into multiple copies, mainly in heterochromatic regions. The frog P. boiei (2n = 22, ZZ♂/ZW♀) is found in the Brazilian Atlantic forest and has an atypical pattern of heterochromatin distribution when compared to other anuran amphibians, with large pericentromeric blocks on all chromosomes. In addition, females of Proceratophrys boiei have a metacentric sex chromosome W showing heterochromatin in all chromosomal extension. In this work, we performed high-throughput genomic, bioinformatic, and cytogenetic analyses to characterize the satellite DNA content (satellitome) in P. boiei, mainly due to high amount of C-positive heterochromatin and the highly heterochromatic W sex chromosome. After all the analyses, it is remarkable that the satellitome of P. boiei is composed of a high number of satDNA families (226), making P. boiei the frog species with the highest number of satellites described so far. Consistent with the observation of large centromeric C-positive heterochromatin blocks, the genome of P. boiei is enriched with high copy number of repetitive DNAs, with total satDNA abundance comprising 16.87% of the genome. We successfully mapped via Fluorescence in situ hybridization the two most abundant repeats in the genome, PboSat01-176 and PboSat02-192, highlighting the presence of certain satDNAs sequences in strategic chromosomal regions (e.g., centromere and pericentromeric region), which leads to their participation in crucial processes for genomic organization and maintenance. Our study reveals a great diversity of satellite repeats that are driving genomic organization in this frog species. The characterization and approaches regarding satDNAs in this species of frog allowed the confirmation of some insights from satellite biology and a possible relationship with the evolution of sex chromosomes, especially in anuran amphibians, including P. boiei, for which data were not available.