Patterns of microchromosome organization remain highly conserved throughout avian evolution.

The structure and organization of a species genome at a karyotypic level, and in interphase nuclei, have broad functional significance. Although regular sized chromosomes are studied extensively in this regard, microchromosomes, which are present in many terrestrial vertebrates, remain poorly explored. Birds have more cytologically indistinguishable microchromosomes (~ 30 pairs) than other vertebrates; however, the degree to which genome organization patterns at a karyotypic and interphase level differ between species is unknown.

Multicolor detection of every chromosome as a means of detecting mosaicism and nuclear organization in human embryonic nuclei.

Fluorescence in-situ hybridization (FISH) revolutionized cytogenetics using fluorescently labelled probes with high affinity with target (nuclear) DNA. By the early 1990s FISH was adopted as a means of preimplantation genetic diagnosis (PGD) sexing for couples at risk of transmitting X-linked disorders and later for detection of unbalanced translocations. Following a rise in popularity of PGD by FISH for sexing and the availability of multicolor probes (5-8 colors), the use of FISH was expanded to the detection of aneuploidy and selective implantation of embryos more likely to be euploid, the rationale being to increase pregnancy rates (referral categories were typically advanced maternal age, repeated IVF failure, repeated miscarriage or severe male factor infertility).

Reconstruction of gross avian genome structure, organization and evolution suggests that the chicken lineage most closely resembles the dinosaur avian ancestor.

Background: The availability of multiple avian genome sequence assemblies greatly improves our ability to define overall genome organization and reconstruct evolutionary changes. In birds, this has previously been impeded by a near intractable karyotype and relied almost exclusively on comparative molecular cytogenetics of only the largest chromosomes. Here, novel whole genome sequence information from 21 avian genome sequences (most newly assembled) made available on an interactive browser (Evolution Highway) was analyzed.

Novel tools for characterising inter and intra chromosomal rearrangements in avian microchromosomes.

Avian genome organisation is characterised, in part, by a set of microchromosomes that are unusually small in size and unusually large in number. Although containing about a quarter of the genome, they contain around half the genes and three quarters of the total chromosome number. Nonetheless, they continue to belie analysis by cytogenetic means.

Nuclear organisation in totipotent human nuclei and its relationship to chromosomal abnormality.

Studies of nuclear organisation, most commonly determining the nuclear location of chromosome territories and individual loci, have furthered our understanding of nuclear function, differentiation and disease. In this study, by examining eight loci on different chromosomes, we tested hypotheses that: (1) totipotent human blastomeres adopt a nuclear organisation akin to that of committed cells; (2) nuclear organisation is different in chromosomally abnormal blastomeres; and (3) human blastomeres adopt a ;chromocentre' pattern. Analysis of in vitro fertilisation (IVF) conceptuses permits valuable insight into the cell biology of totipotent human nuclei.