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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 […]

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 […]

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 […]

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 […]

Autosomal Recessive Inheritance: The principal difficulty with autosomal recessive inheritance is to be sure that this is indeed the mode of inheritance in a particular family. The great majority of cases of an autosomal recessive disorder are born to healthy but heterozygous parents, with no other affected relatives. Vertical transmission, so characteristic of dominant inheritance, […]

Autosomal Dominant Inheritance: Although, in theory, autosomal dominant inheritance is the simplest model for genetic counselling, in practice it provides some of the most difficult problems, with traps for the unwary that require special mention. An autosomal dominant disorder or trait can be defined either by the observed pattern of transmission between generations in families […]