Genetic control of X inactivation and processes leading to X-inactivation skewing

Journal Article · Sat Jun 01 04:00:00 EDT 1996 · American Journal of Human Genetics

OSTI ID:446924

Belmont, J W ^[1]

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1. Baylor College of Medicine, Houston, TX (United States)

The chromosomal basis of sex determination (i.e., XX in females, XY in males) results in an inequality of gene copy number and content between males and females. In humans (and other mammals) the potential imbalance of gene expression from the two X chromosomes in females is resolved by inactivating one X in all the somatic tissues. Beginning in the late blastocyst stage of embryonic development, one of the two X chromosomes is globally down-regulated in each somatic cell, resulting in expression from only one allele at the vast majority of X-encoded loci. While the paternal X is selectively inactive in the extraembryonic tissues (vide infra), in the embryo proper the process of X inactivation is random between the maternal and paternal X chromosomes. The result is that most females have mosaic expression of maternal and paternal alleles of X chromosome loci. The mean contribution from each chromosome is 50%, but because the process is generally random, a normal female may vary considerably from the mean. 67 refs., 1 fig.

• OSTI ID: 446924
• Journal Information: American Journal of Human Genetics, Journal Name: American Journal of Human Genetics Journal Issue: 6 Vol. 58; ISSN AJHGAG; ISSN 0002-9297
• Country of Publication: United States
• Language: English

Related Subjects

55 BIOLOGY AND MEDICINE
BASIC STUDIES
CHROMOSOMAL ABERRATIONS
DNA
DNA REPLICATION
GENE MUTATIONS
GENE REGULATION
GENES
HEREDITARY DISEASES
HUMAN X CHROMOSOME
MAN
METHYLATION
MOSAICISM
ONTOGENESIS
RFLPS
SEX DEPENDENCE
STRUCTURE-ACTIVITY RELATIONSHIPS