Download Assuming that Victoria and/or her descendants were

Challenge Question
September 2008
Albert
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Edward VII
VICTORIA
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George V
Alexandra of
Denmark
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Mary of Teck
|
George VI
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Elizabeth
Bowes-Lyon
|
ELIZABETH II
Assuming that Victoria and/or her descendants were the ONLY
people in Elizabeth II’s ancestry that carried the hemophilia gene, what
is the probability that Elizabeth II herself carries it?
Answer
Zero, unless the gene mutation arose spontaneously. To see why, look at the family tree above.
The mutations for hemophilia are located on the X chromosome. All children inherit an X
chromosome from their mothers, while fathers pass on an X chromosome to their daughters but give a Y
chromosome to their sons. That means that the affected genes can pass from a mother to any child, or
from a father to a daughter, but not from a father to a son.
Elizabeth II, being descended from Victoria through the male line, could not inherit the affected
genes. Estimates vary, but the probability that the hemophilia mutation will arise spontaneously is
around 1 in 15,000-30,000 for Hemophilia A and 1 in 100,000-350,000 for Hemophilia B.
For More Information
“Haemophilia.” Wikipedia. 24 Aug. 2008. Wikimedia Foundation. 25 Aug. 2008
<http://en.wikipedia.org/wiki/Hemophilia>.
McPhee, Stephen J., Maxine A. Papadakis, and Lawrence M. Tierney, eds. Current Medical Diagnosis and
Treatment. 47th ed. New York: McGraw-Hill, 2008. 463-465.
Merck Manual of Medical Information. 2nd ed. New York: Pocket Books, 2003. 999-1000.