tailieunhanh - The Gale Genetic Disorders of encyclopedia vol 1 - part 8

Con của họ có 25% cơ hội thừa kế hai bản sao của gen đột biến và bị ảnh hưởng bởi căn bệnh này, 50% cơ hội thừa kế một bản sao của gen đột biến, và được một tàu sân bay của căn bệnh này nhưng không bị ảnh hưởng và giảm 25% cơ hội kế thừa | Genetic testing their child has a 25 chance of inheriting two copies of the mutated gene and being affected by the disease a 50 chance of inheriting one copy of the mutated gene and being a carrier of the disease but not affected and a 25 chance of inheriting two normal genes. When only one parent is a carrier a child has a 50 chance of inheriting one mutated gene and being an unaffected carrier of the disease and a 50 chance of inheriting two normal genes. Cystic fibrosis is a disease that affects the lungs and pancreas and is discovered in early childhood. It is the most common autosomal recessive genetic disease found in the caucasian population one in 25 people of Northern European ancestry are carriers of a mutated cystic fibrosis gene. The gene located on chromosome 7 was identified in 1989. The gene mutation for cystic fibrosis is detected by a direct DNA test. Over 600 mutations of the cystic fibrosis gene have been found each of these mutations cause the same disease. Tests are available for the most common mutations. Tests that check for the 86 of the most common mutations in the Caucasian population will detect 90 of carriers for cystic fibrosis. The percentage of mutations detected varies according to the individual s ethnic background . If a person tests negative it is likely but not guaranteed that he or she does not have the gene. Both parents must be carriers of the gene to have a child with cystic fibrosis. Tay-Sachs disease also autosomal recessive affects children primarily of Ashkenazi Jewish descent. Children with this disease die between the ages of two and five. This disease was previously detected by looking for a missing enzyme. The mutated gene has now been identified and can be detected using direct DNA mutation analysis. Presymptomatic testing Not all genetic diseases show their effect immediately at birth or early in childhood. Although the gene mutation is present at birth some diseases do not appear until adulthood. If a specific .