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Presents a study that compared electrical defects in germanium[sup+] and silicon[sup+] preamorphized BF2-implanted silicon. Way to avoid the problem of forming shallow p[sup+] regions with low-energy boron ion implantation; Sample preparation and measurement procedures; Results of deep-level transient spectroscopy measurements.

Presents a study which examined the electrical properties of silicon layers implanted with 10 kiloelectronvolts arsenic. Details of the differential Hall-effect profiling; Results; Conclusions.

Presents a study that preamorphized the surface of single-crystal silicon prior to the implantation of low-energy boron-fluorine using high-dose implants. Formation of preamorphization results in shallow junction formation with minimal channeling of the boron; Measurements of leakage current and deep-level defects; Types of electrically active defects.

Presents a study which showed the annealing characteristics of shallow arsenic- and boron-implanted layers. Comparison of isothermal annealing and furnace annealing; Annealing of ion-implanted material profile; Objectives of diffusion modelling.

Presents a study which assessed surface segregation of indium in gallium arsenide (GaAs) during molecular beam epitaxial growth of InAs monolayers between GaAs layers using photoluminescence (PL), secondary-ion mass spectroscopy (SIMS) and cross-sectional transmission electron microscopy measurements. Details of an experiment on GaAs semi-insulating substrates; Description of the PL peaks relating to the InAs layers; Result of SIMS in surface segregation.

The effect of maternal α+-thalassaemia on pregnancy was assessed in the north coastal region of Papua New Guinea (PNG), where malaria is hyperendemic and α+-thalassaemia is extremely common. In a prospective study of 987 singleton hospital deliveries, we correlated maternal α-globin genotype with markers of reproductive fitness (age in primigravidae, gravidity, pregnancy interval and the number of miscarriages and stillbirths), Plasmodium falciparum (P. falciparum) infection of the mother and placenta, maternal haemoglobin, preterm delivery and birthweight. The frequency of the − α genotype in mothers was 0·61. Markers of reproductive fitness were similar in women with and without α+-thalassaemia. Median haemoglobin concentration during pregnancy and after delivery was about 1·0 g/dl lower in homozygous α+-thalassaemia than in women with a normal α- globin genotype ( P ≤ 0·001). The frequency of placental P. falciparum infection and systemic malaria infection after delivery showed no consistent relationship to α-globin genotype. The frequency of preterm delivery and low birthweight did not vary significantly according to maternal α-globin genotype. Maternal α+-thalassaemia does not affect reproductive fitness or susceptibility to malaria during pregnancy. Although median haemoglobin concentration was significantly lower in mothers homozygous for α+-thalassaemia than those with a normal α-globin genotype, this did not result in an adverse outcome of pregnancy. [ABSTRACT FROM AUTHOR]

Polymerase chain reaction protocols were designed specifically to amplify regions of the alpha globin complex that contain the nine common polymorphic haplotyping sites. These reactions provided a quicker and more sensitive approach to determining alpha globin haplotypes than Southern blotting methods. [ABSTRACT FROM AUTHOR]

We have used a new method for binning minisatellite alleles (semi-automated allele aggregation) and report the extent of population diversity detectable by eleven minisatellite loci in 2689 individuals from 19 human populations distributed widely throughout the world. Whereas population relationships are consistent with those found in other studies, our estimate of genetic differentiation (Fst) between populations is less than 8%, which is lower than comparative estimates of between 10%–15% obtained by using other sources of polymorphism data. We infer that mutational processes are involved in reducing Fst estimates from minisatellite data because, first, the lowest Fst estimates are found at loci showing autocorrelated frequencies among alleles of similar size and, second, Fst declines with heterozygosity but by more than predicted assuming simple models of mutation. These conclusions are consistent with the view that minisatellites are subject to selective or mutational constraints in addition to those expected under simple stepwise mutation models. [ABSTRACT FROM AUTHOR]

Analysis of DNA from members of a Melanesian family from Papua New Guinea with haemoglobin (Hb) H disease revealed that all four alpha globin genes are intact in affected subjects. Study of restriction enzyme site and length polymorphisms and the use of oligonucleotide probes indicated that the molecular basis of this Papuan form of non-deletion Hb H disease differs from the previously described Middle Eastern and Mediterranean types. [ABSTRACT FROM PUBLISHER]

A study of the causes of anaemia in the south west Pacific archipelago of Vanuatu has identified one island, Maewo, where the carrier rate for beta thalassaemia exceeds 20%, one of the highest recorded incidences in the world. Homozygous beta thalassaemia is a major cause of infant mortality and a serious drain on health resources on this island. Interactions of beta thalassaemia with various forms of alpha + thalassaemia were common in this population. Coexistent alpha + thalassaemia leads to better haemoglobinised and larger red cells than are seen in simple beta thalassaemia heterozygotes and screening for the latter can only be reliably carried out by Hb A2 estimation. [ABSTRACT FROM PUBLISHER]

New techniques of DNA analysis have been applied to the prenatal diagnosis of the common haemoglobin disorders. Currently, it is possible to provide a comprehensive programme for the prevention of these conditions, although this entails the use of several different techniques including globin chain synthesis analysis, direct identification of mutations with restriction enzymes, linkage analysis of restriction fragment length polymorphisms, and the use of oligonucleotide probes. At present, the best combination of these approaches has to be worked out for individual populations, but as the techniques of chorion villus sampling and DNA analysis improve it should be possible to rationalise these prenatal diagnosis programmes and thus make them simpler and less expensive. [ABSTRACT FROM PUBLISHER]

This report describes a Negro family with the G gamma beta + type of hereditary persistence of fetal haemoglobin. Family members with levels of haemoglobin F of 17 to 23% had normal red cell indices, balanced globin chain synthesis, and a pancellular distribution of the fetal haemoglobin, showing that these subjects have a form of HPFH. The production of Hb A and C in addition to the large amount of Hb F in one family member showed that there was an active beta A gene in cis to the HPFH determinant, while structural analysis of the Hb F revealed the presence of only G gamma chains. The criteria for the diagnosis of G gamma beta + HPFH, and the relevance of such conditions to the control of globin gene expression, are discussed. [ABSTRACT FROM PUBLISHER]

Two new cases of G gamma delta beta thalassaemia and G gamma HPFH (Hb Kenya type) have been characterised in detail and compared with regard to haematological data, globin chains biosynthesis, and intracellular distribution of Hb F. The similarities and differences between these two conditions are discussed in relation to the possible underlying defects at the molecular level and to the control of the gamma delta beta gene complex in general. [ABSTRACT FROM PUBLISHER]

Sixteen subjects, with sickle-cell anaemia, all Iranians (ages 3 to 56 years), with very mild symptomatology are reported. Some of the subjects had been totally asymptomatic. Splenomegaly was noted in 9 cases. There was an increase in the mean level of fetal haemoglobin (18%); this is the probable explanation for the mild phenotype. In 29 subjects with sickle-cell trait, the level of HbF was also significantly raised as compared with normal (1-6% vs. 0-6%). The mechanism of increased synthesis of HbF is unknown. The findings are similar to those reported in the Shiite Moslems of Saudi Arabia suggesting that in these populations there is a genetically-determined ability to produce high levels of Hb F in the presence of the sickle-cell gene. [ABSTRACT FROM PUBLISHER]

Five families are described in which there have been matings between individuals doubly heterozygous for beta thalassaemia and the delta-chain variant haemoglobin A2' to normal persons. In all there were 24 informative offspring. There were no crossovers between the beta-thalassaemia and delta-chain loci; in three of the families the genes were linked in cis and in two families the genes were found in trans. Together with previously reported families there have now been 58 opportunities for crossing over between the beta-thalassaemia and delta-chain loci and there have been two possible and one highly probable crossovers. Of the total of 9 families reported to date 4 have had the genes for beta thalassaemia and Hb A2' in cis and 5 in trans. These findings are contrasted with the findings in families where a beta-chain structural variant and Hb A2' have been observed together and these genes have always been found in trans and never in cis. The reasons for linkage disequilibrium of this type are discussed. It is concluded tentatively that the distance between the delta-structural and beta-thalassaemia loci is greater than that between the delta-structural and beta-structural loci. To date this conclusion can only be applied to the beta+ -thalassaemia and beta-thalassaemia genes as found in the African population, since this is the only population with a high incidence of delta-chain mutants which allow linkage analysis of this type to be carried out. [ABSTRACT FROM PUBLISHER]

The clinical and haematological findings in 19 Liberians probably homozygous for beta thalassaemia are described. The haemoglobin patterns were similar with Hb F levels in the 30-50% range and a raised level of Hb A2 and, although the clinical severity varied widely, over half the cases were symptomless and even the more severely affected ones showed a milder picture than that found in Mediterranean races. Haemoglobin-synthesis studies carried out on three homozygotes and two heterozygotes indicated a variable degree of globin-chain imbalance. The reasons for the mild course of the disease in Liberians and other African races are discussed; it is likely that the beta-thalassaemia genes in these populations are different from those in other racial groups. It is noted that all persons in this study belong to tribes which have a low incidence of the sickle-cell gene. [ABSTRACT FROM PUBLISHER]