ACCESSION NO:  93-94-0813
       TITLE:  Women Leave Indelible Mark on Evolution
      AUTHOR:  WATZMAN, HAIM
     JOURNAL:  New Scientist
    CITATION:  July 24, 1993, 139(1883): 15.
        YEAR:  1993
    PUB TYPE:  Article
 IDENTIFIERS:  IMPRINTED GENES; MECHANISM OF INHERITANCE; EMBRYONIC 
               DEVELOPMENT; OVARIAN TERATOMA; PLACENTAL MOLES; MENDELIAN 
               GENETICS; HUMAN EVOLUTION
ABSTRACT: Women, rather than men, are the most important agents of human evolution, say Israeli scientists, who believe work on gene imprinting has brought the field of genetics and human evolution to a fundamental revolution. Imprinted genes are a part of a minority of genes which are "marked" in a way which results in identical genes inherited from a person's mother and father functioning differently. One is inactive and suppressed, while the other is functional, depending on whether they come from the maternal or paternal line. Imprinted genes have been implicated in several genetic disorders and childhood diseases. In placental mammals, imprinted paternal genes govern placental development, while imprinted maternal genes are involved in embryonic growth.

Abnormal placentas called "moles," formed from the union of an unucleated cell and a sperm, contain only paternal genes and lack counteracting imprinted maternal genes. This results in a placenta without an embryo which grows malignantly. The opposite phenomenon is ovarian teratoma, where an abnormal cell in the ovary develops with a full, rather than the normal half complement of genes. The genes are all maternal. The result is a benign tumor which parallels normal embryonic differentiation, but lacking paternal genes cannot form a placenta.

Since imprinted paternal genes have much to do with providing in-utero nourishment for the fetus, and the imprinted maternal genes are critical in determining the way the fetus develops, researchers believe that womankind, rather than mankind, has been the key to human evolution. For human evolution to proceed, favorable mutations must be passed on to the next generation. A paternally imprinted inherited gene will not be expressed in embryonic or later development, whereas an imprinted maternal gene will always be expressed. This pattern of genetic inheritance completely upsets the classical model of Mendelian genetics. The discovery of imprinted genes means that while the simple dominant-recessive model is true for most genes it cannot explain a small but critical group.