Chapter 11.1, Problem 32E

Genetics of Cystic Fibrosis Cystic fibrosis is one of the most common inherited diseases in North America (including the United States), occurring in about 1 of every 2000 Caucasian births and about 1 of every 250.000 non-Caucasian births. Even with modern treatment, victims usually die from lung damage by their early twenties.

If we denote a cystic fibrosis gene with a c and a disease-free gene with a C (since the disease is recessive), then only a cc person will actually have the disease. Such persons would ordinarily die before parenting children, but a child can also inherit the disease from two Cc parents (who themselves are healthy—that is. have no symptoms but are "carriers" of the disease). This is like a pea plant inheriting white flowers from two red-flowered parents that both carry genes for white.

Among 150,000 North American Caucasian births, about how many occurrences of cystic fibrosis would you expect?