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Chromosome: All 23 pairs of human chromosomes can be distinguished microscopically from each other, and much fine detail within each chromosome can also be recognised. An agreed international system of nomenclature, reviewed at regular intervals, forms the basis of reports from laboratories. Although these reports will usually include an explanatory text or be accompanied by […]

COPY NUMBER VARIANTS The ability to detect chromosomal deletions and duplications through the microscope has been limited: only the larger deletions or duplications have been detected. Several approaches have been developed to improve our recognition of such copy number variants (CNVs). Three approaches are mentioned here: Fluorescence in situ hybridisation (FISH) This uses fluorescent-labelled DNA […]

Malformation Syndromes: It is important to establish aetiology, where possible, for practical reasons of genetic counselling, but some of these disorders are proving to be of great importance in basic research, particularly where specific genes are involved. As the techniques of molecular genetics are applied to dysmorphology, many more syndromes will prove useful as models […]

WHAT DO WE MEAN BY ‘CARRIER’? The term ‘carrier’ is widely used in medicine. It is often applied to those harbouring an infective agent but not overtly sick because of it, quite apart from its use in medical genetics. The term may be used by different people with entirely different connotations, and a precise definition […]

Prenatal Diagnosis: The development of techniques for diagnosing genetic disorders in utero was a major advance in medical genetics and has so altered the outlook for families at risk of having affected children that it has become one of the main options open to those receiving genetic counselling, especially where there is a high risk […]

TREATMENT FOR GENETIC DISEASES In comparison with other types of disease, such as major infections, nutritional deficiencies or even cancers, most genetic disorders has been relatively unresponsive to treatment or to primary preventive measures. As these other disease categories have become less common, so the relative contribution of genetic disorders has increased. It is this, […]

MUSCULAR DYSTROPHIES Many, indeed most, neuromuscular disorders have a Mendelian basis. Partly for this reason, and partly because of the severe chronic disability produced by many of them, they represent a major category of genetic counselling requests and referrals. The muscular dystrophies, a large group of progressive, primary muscle disorders, form a particularly important problem, […]

It is possible for a pregnancy test to show a negative result one day and a positive result the next day. There are several factors that can cause this change, such as the timing of the test in relation to ovulation and implantation, the concentration of the hormone hCG in the urine, and the sensitivity of the pregnancy test. It is important to follow the instructions of the pregnancy test and, if in doubt, consult with a healthcare professional for further guidance.