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At least 19 recordsLinked to original sources
PubMed1992

Characterization of a new repetitive sequence that is enriched on microchromosomes of turkey.

We cloned and characterized a new highly repetitive, species-specific DNA sequence from turkey (Meleagris gallopavo). This repeat family, which accounts for approximately 5% of the turkey genome, consists of a 41 bp repeated element that is present in tandem arrays longer than 23 kb. In situ hybridization to turkey metaphase chromosomes (2n = 80) demonstrated that this sequence was located primarily on certain microchromosomes: approximately one-third of the 66 microchromosomes showed a positive signal. With respect to the macrochromosomes, hybridization was seen only in a pericentric position on nos. 2 and 3. The turkey microchromosome (TM) sequence shares motifs (alternating A3-5 and T3-5 clusters separated by 6-8 bp) that have been found previously in other avian tandemly repeated elements, e.g. a chicken microchromosomes sequence, and W (female) chromosome-specific sequences of chicken and turkey. However, the TM sequence does not cross-hybridize under moderately stringent conditions with these other sequences. The spread and amplification of related repetitive sequence elements on microchromosomes and W chromosomes is discussed.

Animals↗
PubMed1979

Discovery of an inherited bisatellited metacentric microchromosome in amniotic cell culture.

The identification is reported of an extra bisatellited metacentric microchromosome in amniotic cell culture from the third pregnancy of an identical twin (amniocentesis being performed because of age), and its subsequent finding in the maternal parent as an inherited familial marker. The carriers of the microchromosome are all clinically normal and the parents opted for continuation of pregnancy. Only one other report was found in the literature of a similar microchromosome detected in amniotic fluid culture, but we believe ours to be the first bisatellited microchromosome to be clearly identified from an amniotic cell culture using silver staining.

Adult↗
PubMed1977

[Change in the microchromosome number in the process of macrochromosome spiralization in Gallus domesticus].

A correlation of mitotic spiralization of macrochromosomes with a change in the number of microchromosomes is detected. A wave character of microchromosomes variability during spiralization of macrochromosomes is suggested to be due to reversible despiralization of microchromosomes, which is probably a result of the colchicin treatment. Metaphase plates where the range of chromosome 1 length is from 10.5 to 12mu are recommended to calculate the number of microchromosomes.

Animals↗
PubMedDate not supplied

A familial bisatellited extra metacentric microchromosome in man.

A bisatellited, extra metacentric microchromosome was found in a normal male and his father. This extra marker participated in satellite association in over 50 percent of the cells; silver-staining revealed only one active NOR region. Other banding studies identified two other cytogenetic "markers" in the family-a 9qh+ and a 21s+. Risk for a carrier of such a microchromosome is probably low but cytogenetic amniocentesis is recommended to rule out aneuploidy in the fetus.

Cell Nucleolus↗
PubMed1992

Microchromosomal assignment of the chicken ovotransferrin and adenylate kinase genes.

Ovotransferrin, an egg-white protein implicated in the transfer of trace elements from the hen oviduct to the developing avian embryo, and cytosolic adenylate kinase, an essential enzyme involved in the interconversion of adenine nucleotides in energetically active tissues, have been mapped to two separate chicken microchromosomes by fluorescent in situ hybridization. Considering present and previous data, the possibility of loss of intron material resulting in the compactation of genes in chicken microchromosomes is briefly discussed.

Adenylate Kinase↗
PubMed1977

Chicken macrochromosomes contain an endogenous provirus and microchromosomes contain sequences related to the transforming gene of ASV.

Chicken chromosomes from a euploid Marek's lymphoma cell line have been partially fractionated according to size by rate zonal centrifugation in a zonal rotor. DNA-DNA hybridization tests, using unlabeled DNA extracted from gradient fractions and labeled single-stranded, virus-specific DNAs prepared in vitro, indicate that large macrochromosomes harbor the provirus for the endogenous RNA tumor virus of chickens (RAVO), whereas a cellular sequence related to the transforming gene of avian sarcoma virus (ASV) is located in microchromosomes. In support of the method, we have also shown that the single gene for ovalbumin can be assigned to macrochromosomes.

Alpharetrovirus↗
PubMed1978

Significance of detection of extra metacentric microchromosome in amniotic cell culture.

A metacentric bisatellited microchromosome was detected in all metaphases from an amniotic culture performed because of maternal age. A wide-ranging survey of the literature failed to disclose any consistent anomaly associated with such a marker, but did reveal that the clinical picture of patients manifesting it could range from complete normality through mental retardation to a variety of deformities. The parents elected for termination, and the only deformity detected in the abortus was fixed talipes equinovarus. The implications of the finding of this marker chromosome on amniocentesis, believed to be reported for the first time here, are discussed particularly in the context of genetic counselling.

Adult↗
PubMed2026

A chromosome-level, haplotype-resolved genome assembly for the barn owl, Tyto alba.

Recent advances in long-read sequencing have enabled near telomere-to-telomere (T2T) assemblies across diverse taxa. However, avian genomes remain challenging due to numerous microchromosomes, small, typically < 20Mb, DNA molecules that are gene-, GC-, and repeat-rich. As a consequence, microchromosomes are often missing from genome assemblies. Here, we present a chromosome-level, haplotype-resolved genome assembly for the Western barn owl (Tyto alba). Using a trio-binning strategy with Illumina parental reads combined with PacBio HiFi and Oxford Nanopore Technologies data, we generated two phased contig sets. These were scaffolded into 40 linkage groups using a linkage map. Comparative analyses identified unplaced HiFi scaffolds corresponding to microchromosomes, which we integrated into six additional microchromosomes using long reads information. The two assemblies present 46 chromosomes, matching the karyotype of the species. They exhibit strong synteny between parental haplotypes, except for a &#x223c;38 Mb complex region on chromosome 7 containing nested inversions. This high-quality reference provides a haplotype-resolved and chromosome-level genome for Strigiformes, enabling fine-scale studies of structural variation and avian genome evolution.

Tyto alba↗
PubMed2024

Comparative genomics illuminates karyotype and sex chromosome evolution of sharks.

Chondrichthyes is an important lineage to reconstruct the evolutionary history of vertebrates. Here, we analyzed genome synteny for six chondrichthyan chromosome-level genomes. Our comparative analysis reveals a slow evolutionary rate of chromosomal changes, with infrequent but independent fusions observed in sharks, skates, and chimaeras. The chondrichthyan common ancestor had a proto-vertebrate-like karyotype, including the presence of 18 microchromosome pairs. The X chromosome is a conversed microchromosome shared by all sharks, suggesting a likely common origin of the sex chromosome at least 181 million years ago. We characterized the Y chromosomes of two sharks that are highly differentiated from the X except for a small young evolutionary stratum and a small pseudoautosomal region. We found that shark sex chromosomes lack global dosage compensation but that dosage-sensitive genes are locally compensated. Our study on shark chromosome evolution enhances our understanding of shark sex chromosomes and vertebrate chromosome evolution.

Animals↗
PubMed1976

The chromosomal localisation of satellite DNA in Ptyas mucosus (Ophidia, Colubridae).

Ptyas mucosus male DNA has a repetitious DNA satellite (p = 1.700 g cm-3) constituting 5% of the haploid genome. In situ hybridisation of radioactive complementary RNA (cRNA) has revealed that satellite sequences are located in the centromeric region of one pair of macrochromosomes and in the terminal region of 8 pairs of microchromosomes. These regions are constitutively heterochromatic as revealed by C-banding. The possibility of involvement of satellite rich microchromosomes in nucleolus organisation is discussed.

Animals↗
PubMed1992

Evolutionary patterns in chromosome numbers in neotropical Lepidoptera. I. Chromosomes of the Heliconiini (family Nymphalidae: subfamily Nymphalinae).

Chromosome counts in meiotic metaphase plates in the gonads of 67 of the probable 68 species of mimetic neotropical heliconian butterflies (Nymphalidae), representing 1524 individuals in 617 subspecies and geographically separate populations from southern Texas to northern Argentina, revealed a consistent haploid number of n = 21 in the genus Heliconius (except for the most advanced species with n = 33, 37, 56, and 60) and n = 31 in the more primitive genera (Eueides, Dryas, Dryadula, Agraulis, and Dione), with a transitional genus (Neruda) showing three species with n = 28-32, 21-22 + 5-10 "microchromosomes", and 20-22 + 1-5 "microchromosomes". The genus Laparus, with a single polymorphic species doris, probably an offshoot of early Heliconius, shows wide karyotypic variation (n = 20-30, 38) sometimes even within a single individual. The two most primitive genera also show much variation: Podotricha has two species with n = 9 and n = 26-29; and Philaethria shows many phenotypically similar species, two with n = 29 and a still uncertain number (at least 3) with n = 88 (most common), 67-72 (most widespread), 62 (very restricted geographically), 52, 21, and 12. Several interspecific hybrids (Heliconius cydno x H. melpomene) showed normal chromosome pairing, while deficient pairing was seen in intersubspecific hybrids in Eueides tales and Heliconius sara. The importance of these results in the evolutionary study of polytypic tropical species is discussed.

Animals↗