A truncated human chromosome 16 associated with alpha thalassaemia is stabilized by addition of telomeric repeat (TTAGGG)n

Article Abstract:

Telomeres are specialized structures at the end of chromosomes which seem to stabilize the chromosome arrangement and prevent the inappropriate sticking of other chromosomes. In humans, the telomere consists of DNA sequences from 2,000 to 20,000 bases long, consisting of repeats of the sequence TTAGGG. The formation and maintenance of the telomere is poorly understood. Recently, a family with alpha-thalassemia has been found which illustrates the protective role of the telomere and also demonstrates that a telomere may be added to a broken chromosome. In a search for families with unique mutations leading to thalassemia, a man was identified with a relatively severe form of thalassemia, marked by the presence of hemoglobin H. Patients with this genetic disorder are usually lacking three of the four normal globin genes necessary to make normal hemoglobin. In this individual, the mutation was reflected by a truncation of the short arm of chromosome 16. When the genetic material at the end of this chromosome was accidentally lopped off, the necessary globin genes were lost and thalassemia resulted. However, genetic analysis of the patient revealed that the truncated end of the chromosome was capped with a normal telomere. Investigation of family members revealed that this abnormal truncated chromosome 16 was genetically passed on in a stable fashion. This observation reveals two key features of the telomere. A normal telomere may be added to a truncated chromosome, and this telomere is apparently sufficient to ensure that the abnormal chromosome is passed on as a stable unit. There is no reason to believe that this phenomenon would be limited to one case of thalassemia, and it should be expected that similar mechanisms may be at work wherever a truncated chromosome might be found. (Consumer Summary produced by Reliance Medical Information, Inc.)

Genetic disorders

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High incidence of malaria in alpha-thalassaemic children

Article Abstract:

An epidemiological study of children on the island of Espiritu Santo in Vanuatu revealed a higher incidence of malaria in alpha-thalassaemic children, an effect most pronounced in the youngest children and for the less virulent malarial parasite Plasmodium vivax. The increased malaria incidence among alpha-thalassaemic children may be due to their beneficial ability to increase susceptibility to P. vivax, which acts as a natural vaccine and generates increased immunity, thus reducing the likelihood of a fatal or life-threatening attack.

Malaria, Plasmodium vivax

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Providing a little stability

Article Abstract:

Molecular geneticists have successfully created mammalian artificial chromosomes and inserted them into human cells as functional genetic material. The innovative research is potentially more useful than other techniques in human gene therapy because, unlike therapeutic deoxyribonucleic acid, it will provide a long-term solution to inadequacies in gene expression.

Research, Molecular genetics, Human chromosomes

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