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Biomedical Reviews

Sex differences in genetic mechanisms for mammalian brain and behavior

Stephen C. Maxson


There are sex specific genetic mechanisms for mammalian brain and behavior. These are genes that act differently in each sex. They may underlie either similarities or differences in brain and behavior of males and females. Some of these genes are autosomal. Others are located on the non-recombining part of the Y chromosome. Genes on this region of the Y chromosome may contribute to sex differences in brain and behavior in three ways. First, a gene may be on the Y chromosome and not on any other chromosome. Thus, it acts only in males. Sex-determining region on the Y chromosome (Sry) is such a gene. Second, there may be different isoforms of proteins coded for by the gene on the Y chromosome and by its homologue located elsewhere in the genome. Such a gene is Smcy which codes for an H-Y antigen. Smcx is its X-chromosomal homologue. Third, there may be different protein levels in males and females for a gene located on the X and Y chromosomes. Zfy and Zfx, for the zinc finger proteins on the Y and on the X, are a pair of such genes. Due to X inactivation in females, one copy of Zfx is expressed in all tissues of female mice, whereas two copies, one of Zfx and one of Zfy, are expressed in many tissues of male mice.

Biomedical Reviews 1997; 7: 85-90.

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About The Author

Stephen C. Maxson
University of Connecticut
United States

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