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  1. On consanguineous marriages and the genetic load
    Chakraborty R, Chakravarti A
    Hum Genet, 1977 Apr 07;36(1):47-54.
    PMID: 870410
    It has been reported that studies of the genetic consequences of inbreeding should adopt a different strategy in populations having a relatively old inbreeding history and where inbreeding levels have varied over time. This contention is tested with a series of 39,495 single-birth records from Bombay, India, collected in a World Health Organization survey on congenital malformations. Our analysis reveals that: 1. the incidence of major malformations is significantly higher among the inbred offspring (1.34%) as compared to that among non-inbred ones (0,81%)--a finding at variance with a previous study in the same area; 2. the inbreeding effect on perinatal mortality (stillbirths and mortality during the first few days of life) is also found to be significant. In view of the above findings, the genetic load as disclosed by inbreeding is computed for perinatal mortality, major malformations and pooling these together. A + B, the measure of the number of lethal equivalents per gamete, is found to be at variance with other reports. Such variability can be ascribed to non-genetic factors. Supporting evidence collected from Brazil and Malaysia in the same survey is also presented.
    Matched MeSH terms: Genes, Lethal
  2. Fulltext Mechanisms of sex determination and transmission ratio distortion in Aedes aegypti
    Hoang KP, Teo TM, Ho TX, Le VS
    Parasit Vectors, 2016 Jan 28;9:49.
    PMID: 26818000 DOI: 10.1186/s13071-016-1331-x
    BACKGROUND: More effective mosquito control strategies are urgently required due to the increasing prevalence of insecticide resistance. The sterile insect technique (SIT) and the release of insects carrying a dominant lethal allele (RIDL) are two proposed methods for environmentally-friendly, species-targeted population control. These methods may be more suitable for developing countries if producers reduce the cost of rearing insects. The cost of control programs could be reduced by producing all-male mosquito populations to circumvent the isolation of females before release without reducing male mating competitiveness caused by transgenes.

    RESULTS: An RNAi construct targeting the RNA recognition motif of the Aedes aegypti transformer-2 (tra-2) gene does not trigger female-to-male sex conversion as commonly observed among dipterous insects. Instead, homozygous insects show greater mortality among m-chromosome-bearing sperm and mm zygotes, yielding up to 100% males in the subsequent generations. The performance of transgenic males was not significantly different to wild-type males in narrow-cage competitive mating experiments.

    CONCLUSION: Our data provide preliminary evidence that the knockdown of Ae. aegypti tra-2 gene expression causes segregation distortion acting at the level of gametic function, which is reinforced by sex-specific zygotic lethality. This finding could promote the development of new synthetic sex distorter systems for the production of genetic sexing mosquito strains.

    Matched MeSH terms: Genes, Lethal/genetics
  3. The Malaysian experience in the typing of genetic variants of alpha-1-antitrypsin
    Desa NM, Ismail Z, Beran Z, Musa SH
    Southeast Asian J. Trop. Med. Public Health, 1995;26 Suppl 1:311-4.
    PMID: 8629132
    It is known that alpha1-antitrypsin deficiency is associated with emphysema in adults and liver cirrhosis in neonates. The phenotypes PiZZ and PiSZ are considered to be high risk groups. alpha1-antitrypsin deficiency is one of the most common lethal congenital disorders in Europe and the USA, occurring in approximately 1 in 2,000 caucasians of North European descent. Studies in Malaysia have found that the phenotypes PiZ and PiS are present in our population. Out of 950 samples analyzed, it was found that 10 samples were shown to be apparently Z homozygous phenotype. The phenotype is determined by high resolution isoelectrofocusing on an ultra-thin polyacrylamide gel embedded with narrow range Pi phamarlyte. The isoelectrofocused bands are confirmed by immunofixation and the plasma alpha1-antitrypsin levels determined by electroimmunoassay. The abnormal phenotypes are further confirmed by polymerase chain reaction using allele specific oligonucleotides.
    Matched MeSH terms: Genes, Lethal
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