Jewish genealogy
Our genes are our destiny. Genes are segments of DNA that constitute a single functional unit, i.e. that express a single protein or equivalent function. Genes are organized in the nucleus of the cell into chromosomes. There are 22 pairs of chromosomes in the human genome (the sum of all human genes) plus the two sex chromosomes X and Y (XX for a female and XY for a male). The physical expression of gene function, such as blue eyes or blonde hair, is called the phenotype. It the 1860s the monk Gregor Mendel in Brno, Czechoslovakia, discovered using pea plants that each gene exists in two forms, dominant and recessive. For example, red hair color among humans is a rare pheotype because it is a double recessive trait, both parents have to carry the gene for red hair, while other hair colorings are dominant.
The current explosion of work on DNA results in large part from the invention in 1985 by Kary Mullis of the process known as PCR (polymerase chain reaction), which enables the copying of small amounts of DNA so that large enough amounts can be obtained for sequence identification. For this discovery he won the Nobel Prize in 1993. The analysis of DNA can result in the determination of guilt or innocence of a crime or a rape or the identity of the parent of a child. It can also help to identify groups that share common genetic origins.
The process of DNA analysis is usually to take the amplifed DNA from PCR and then subject it to selective cleavage by enzymes known as restriction endonucleases, i.e. that cut the DNA at a few specific sites. Then specific fragments (in number and length) are obtained that can be used to characterize that DNA. The fragments are visualized as bands after the DNA mixture is subjected to gel electrophoresis (the DNA fragments being negatively charged they are attracted to the positively charged electrode). In this way a pattern can be obtained that is characteristic of an individual's DNA or genes. To follow the father's (patrilineal) line it is convenient to analyze the Y-chromosome, because it has only 27 genes. To follow the mother's (matrilineal) line it is convenient to use the DNA found in mitochondria (the only non-genetic DNA in the cell).
Over eons of years mutations occur in the DNA of the gene, e.g. by a single chemical deletion or by translocation of chromosmal fragments. These mutations might have no effect, but they might cause a human disease, such as cystic fibrosis or sickle cell anemia, and they might be passed down the generations. In this way genetic markers of specific groups can be observed, such as the degenerative neurological disease known as Tay-Sachs, which is found only among Jews. Since this is a fatal (double recessive) disease, Jewish couples are counselled to get genetic testing before marriage.
Actually there is one other group among which Tay-Sachs is found, and that is the Cajuns of southern Louisiana. Apparently during their voyage from Arcadia (Newfoundland, Canada) to Louisiana in the early 1700s, there must have been intermixing with Jews and the genes for Tay-Sachs were transferred to them. They call the disease "the Jewish sickness."
Another disease commonly found among Jews is Familial Mediterranean fever (FMF), which is also found among other Mediterranean groups. However, sickle cell anemia, which is due to a single mutation in hemoglobin, is found among Africans, Arabs and Greeks, but not among Jews. These genes show selective distribution.
It has been reported that there is a "Cohen gene," and this is not so surprising since Cohanim are a selected stock in which both the mother is Jewish and the father is a Cohen. Realizing this Dr. Karl Skorecki of Hebrew University investigated several hundred Cohanim for common genetic features (fragment patterns) of their Y-chromosome and found a similarity which he called the "Cohen modal Haplotype" (CMH) (haploid refers to a multiple fragment similarity) that was found in 98% of his Cohen subjects, but in only 2-3% of the control of non-Cohen Jews. This was published in a regular refereed scientific journal and is accepted as valid. Subsequent studies have confirmed this finding, although the percentages found were less and it should be noted that this is not a "Cohen gene" but a pattern of gene fragments.
Some Orthodox Jews and organizations have jumped on these findings to argue that the Bible is supported by science. But, they also often dispute the genetic evidence for evolution, obtained by the same methods. Other anti-religious groups have called these findings "racist." However, there is no doubt that aspects of human evolution and group relationships can be evaluated by genetic analysis. By doing comparisons of gene fragment patterns it has been ascertained that Jews are more closely related to Kurds than to Arabs. But, these conclusions are subject to doubt, first because of intermixing (there are Kurdish Jews) and because of the caution applied to all conclusions based on statistics.
While human group genetic analysis can be politically sensitive, there is no doubt that these type of analyses are increasingly common. However, so far there is no such thing as a "Jewish gene" and there is not likely to be one given the extensive intermixing of Jews with other groups over time.
The current explosion of work on DNA results in large part from the invention in 1985 by Kary Mullis of the process known as PCR (polymerase chain reaction), which enables the copying of small amounts of DNA so that large enough amounts can be obtained for sequence identification. For this discovery he won the Nobel Prize in 1993. The analysis of DNA can result in the determination of guilt or innocence of a crime or a rape or the identity of the parent of a child. It can also help to identify groups that share common genetic origins.
The process of DNA analysis is usually to take the amplifed DNA from PCR and then subject it to selective cleavage by enzymes known as restriction endonucleases, i.e. that cut the DNA at a few specific sites. Then specific fragments (in number and length) are obtained that can be used to characterize that DNA. The fragments are visualized as bands after the DNA mixture is subjected to gel electrophoresis (the DNA fragments being negatively charged they are attracted to the positively charged electrode). In this way a pattern can be obtained that is characteristic of an individual's DNA or genes. To follow the father's (patrilineal) line it is convenient to analyze the Y-chromosome, because it has only 27 genes. To follow the mother's (matrilineal) line it is convenient to use the DNA found in mitochondria (the only non-genetic DNA in the cell).
Over eons of years mutations occur in the DNA of the gene, e.g. by a single chemical deletion or by translocation of chromosmal fragments. These mutations might have no effect, but they might cause a human disease, such as cystic fibrosis or sickle cell anemia, and they might be passed down the generations. In this way genetic markers of specific groups can be observed, such as the degenerative neurological disease known as Tay-Sachs, which is found only among Jews. Since this is a fatal (double recessive) disease, Jewish couples are counselled to get genetic testing before marriage.
Actually there is one other group among which Tay-Sachs is found, and that is the Cajuns of southern Louisiana. Apparently during their voyage from Arcadia (Newfoundland, Canada) to Louisiana in the early 1700s, there must have been intermixing with Jews and the genes for Tay-Sachs were transferred to them. They call the disease "the Jewish sickness."
Another disease commonly found among Jews is Familial Mediterranean fever (FMF), which is also found among other Mediterranean groups. However, sickle cell anemia, which is due to a single mutation in hemoglobin, is found among Africans, Arabs and Greeks, but not among Jews. These genes show selective distribution.
It has been reported that there is a "Cohen gene," and this is not so surprising since Cohanim are a selected stock in which both the mother is Jewish and the father is a Cohen. Realizing this Dr. Karl Skorecki of Hebrew University investigated several hundred Cohanim for common genetic features (fragment patterns) of their Y-chromosome and found a similarity which he called the "Cohen modal Haplotype" (CMH) (haploid refers to a multiple fragment similarity) that was found in 98% of his Cohen subjects, but in only 2-3% of the control of non-Cohen Jews. This was published in a regular refereed scientific journal and is accepted as valid. Subsequent studies have confirmed this finding, although the percentages found were less and it should be noted that this is not a "Cohen gene" but a pattern of gene fragments.
Some Orthodox Jews and organizations have jumped on these findings to argue that the Bible is supported by science. But, they also often dispute the genetic evidence for evolution, obtained by the same methods. Other anti-religious groups have called these findings "racist." However, there is no doubt that aspects of human evolution and group relationships can be evaluated by genetic analysis. By doing comparisons of gene fragment patterns it has been ascertained that Jews are more closely related to Kurds than to Arabs. But, these conclusions are subject to doubt, first because of intermixing (there are Kurdish Jews) and because of the caution applied to all conclusions based on statistics.
While human group genetic analysis can be politically sensitive, there is no doubt that these type of analyses are increasingly common. However, so far there is no such thing as a "Jewish gene" and there is not likely to be one given the extensive intermixing of Jews with other groups over time.
posted by Jack Cohen at 8:34 AM
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