'incest' and genetics...

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Offline CluelessAboutScience

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'incest' and genetics...
« on: 28/07/2009 08:08:26 »
I'm looking for some studies that give hard numbers here.  Doing a google hasn't given me anything in the first 20 hits except 2 differing claims about cousin offspring, one of which claims 4% risk of birth defects and the other claiming 6-8%.  Also one claiming 25%-50% for father/daughter and brother/sister.  However, neither claimant cites a source.  So, anyone?  Just to be clear, I'm looking for the percentage of birth defects that occurs among first cousin offspring, father/daughter offspring and brother/sister offspring and some sources for the figures, please.  If there are conflicting studies, let me know this.  No bias, please.

Oh, and Thanks.


Offline Pwee

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'incest' and genetics...
« Reply #1 on: 28/07/2009 10:02:15 »
I coldn't find any helpful full text articles, but I found these abstracts with pubmed search that can help you:

J Pediatr. 1982 Nov;101(5):854-7.Links
    Children of incest.
    Baird PA, McGillivray B.

    Twenty-nine children of brother-sister or father-daughter matings were studied. Twenty-one were ascertained because of the history of incest, eight because of signs or symptoms in the child. In the first group of 21 children, 12 had abnormalities, which were severe in nine (43%). In one of these the disorder was autosomal recessive. All eight of the group referred with signs or symptoms had abnormalities, three from recessive disorders. The high empiric risk for severe problems in the children of such close consanguineous matings should be borne in mind, as most of these infants are relinquished for adoption.

Int J Legal Med. 2009 Mar 13. [Epub ahead of print]Click here to read Links
    Psychomotor developmental delay and epilepsy in an offspring of father-daughter incest: quantification of the causality probability.
    Schmidtke J, Krawczak M.

    Institut für Humangenetik, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany, schmidtke.joerg@mh-hannover.de.

    A 20-year-old offspring of father-daughter incest, who has been suffering from serious psychomotoric health problems since early childhood, is seeking financial compensation under the German federal act of victim indemnification. For her appeal to be valid, the probability X that the incest was causal for her disorder must exceed 50%. Based upon the available medical records, we show that this is indeed the case and that X is even likely to exceed 65%, thereby rendering the victim's claim scientifically and legally justified.

J Ment Defic Res. 1990 Dec;34 ( Pt 6):483-90.Links
    Incest and mental handicap.
    Jancar J, Johnston SJ.

    Stoke Park Hospital, Stapleton, Bristol, England.

    This is probably the first retrospective study of an adult mentally handicapped population of incestuous parentage. Eleven known incestuous unions were identified with 38 offspring, of whom 15 were admitted to the Stoke Park group of hospitals. Incest and its legal definition in different societies are considered. The effects of close inbreeding on mortality, morbidity, mental function and adoption are examined. The study also reaffirms that incest is one of the causes of mental handicap in a high percentage of offspring.

I'd say that there is no definite answer to the exact percentage, as it highly depends on the genetic backgrond of the family in all cases.