Meiosis and Odd Numbers
Date: December 2004
What is the result of an odd number of chromosomes in a
female (i.e. 22 pairs and 1 odd chromosome?
This condition is known as trisomy and it occurs in both males and females. In the
case of trisomy 21, there are 3 copies of chromosome #21 and it results in Down's
syndrome. The affected child has 47 chromosomes and is severely mentally retarded.
This is the most common cause of mental retardation in children and occurrs in
approximately one in 250 births of mothers 35 years old and older. It is apparently
caused by a mistake during meiosis in older mothers.
Ron Baker, Ph.D.
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Update: June 2012