Experience of course works using cell culture technologies of classical cytogenetics

В статье обобщается опыт написания курсовых работ по разделу цитогенетики и освоения основных методик культивирования, приготовления и окрашивания хромосомных препаратов студентами на кафедре биологии, медицинской генетики и экологии КГМУ. The article summarizes the experience of writing course works on cytogenetics and mastering the basic methods of cultivation, preparation and staining of chromosomal preparations by students at the Department of Biology, Medical Genetics and Ecology of KSMU

7q35q36.3 Deletion and Concomitant 20q13.2q13.33 Duplication in a Newborn: Familiar Case

Array-CGH is a powerful tool in identifying and characterizing complex genomic rearrangements when classical cytogenetics approaches are not sensible enough in detecting rearrangements smaller than 5-10 Mb. The use of Array-CGH has increased the detection rate of unbalanced cryptic rearrangements such as deletions and/or duplications of 10-20% We present here the first report of a patient with 7q35q36.3 microdeletion and concomitant 20q13.2q13.33 microduplication detected by array-CGH and confirmed by reiterative FISH experiments associated with dysmorphism, delayed development, Long QT syndrome (LQTS), complex congenital heart disease, pulmonary hypertension, hypotonia, respiratory distress, cognitive deficit. We proved that this unbalanced rearrangement was due to an adjacent-1 segregation inherited by the mother carrier of a balanced translocation between chromosomes 7 and 20.

Analysis of the embryos genetic characteristics and methodologies of human translocations research

Aim. Assessment of the embryos genetic characteristics from translocation carriers and analysis of the translocation research methodology. Methods. The chromosome structure was analyzed using classical cytogenetics methods, GTG, FISH. Preimplantation genetic testing to identify structural rearrangements of the embryos chromosomes was performed on trophectoderm cells using NGS and FISH methods. Results. The proportion of translocation carriers in the sample of patients with reproductive disorders (n = 6156) was 1.1 %, with 0.4 % – for Robertson translations and 0.8 % for reciprocal ones. 5-day-old embryos with balanced reciprocal translocations are 3-4 times less than with unbalanced ones. Euploid embryos with balanced variants from translocation carriers-mothers and -fathers, amounted to 14.3 % and 12.5 %. Aneuploid embryos with unbalanced translocations accounted for 59.2 % of mothers and 63.2 % of fathers of all received embryos, 80.6 % and 77.8 % of unbalanced ones. Conclusions. Understanding the prevalence of segmental karyotype disorders among the population and modern research methods allows to optimize reproductive care for patients. Keywords: reciprocal translocations, embryos, PGT-SR, NGS, FISH.

Insertions

Insertions are a type of translocation, and indeed they are sometimes referred to as “insertional translocation,” “interstitial translocation,” or “nonreciprocal translocation.” Here, a segment of one chromosome is removed and inserted within another chromosome (in contradistinction to the usual translocation, in which the translocated segment is attached to the end of a recipient chromosome). It is, essentially, a one-way translocation; that is, there is no reciprocal movement back to the originating chromosome. Insertions are rare rearrangements, at the level of detection according to classical cytogenetics. Insertions have their own specific qualities that influence risk assessment, and these are discussed in this chapter.

Elements of Medical Cytogenetics

Chromosome is a combination of Greek words meaning colored (chrom) body (soma). Albeit that molecular methodologies have substantially taken over from classical cytogenetics, and providing a different view of the genetic material, the word chromosome will surely last forever. This chapter provides a very brief historical introduction, and a basic introduction to what chromosomes are, and the ways in which they can be abnormal. The distinction is made between disorders in which there is an excess (trisomy, duplication) of chromosome material, and those in which there is a deficiency (monosomy, deletion). Ethical questions are rehearsed that may arise in the context of the clinical management of chromosome abnormalities.

Gardner and Sutherland’s Chromosome Abnormalities and Genetic Counseling

Medical geneticists and genetic counselors regularly see families attending the genetic counseling clinic with questions about chromosome abnormalities. These families may themselves have had a child affected with a chromosome condition; or, there may have been a history elsewhere in the family. The presentation may have been due to infertility or reproductive loss. Questions may include the following: What is known about this condition? What caused this to happen? Is it likely to happen again? If so, is there a way to prevent it from happening again? The power of molecular approaches to chromosome analysis, coming to be routinely available in this second decade of the twenty-first century, has brought to our knowledge many new “chromosomal syndromes” to add alongside those long known from the days of classical cytogenetics. This new knowledge has increased our ability to answer the questions that families may have; but equally, it has raised challenges in interpretation, as molecular karyotyping has revealed more complexity in the way the human genome is constructed. This book distils the knowledge that has evolved in recent and olden times, and it presents the information in a way that will be helpful to the practitioner. In particular, the risks of recurrence, or of occurrence, of a particular chromosome disorder are clearly set forth. The application of chromosomal knowledge to reproductive conditions, both diagnostically and in management, is rehearsed.