Answer: In Recessive mutations two copies of a disease allele are required for an individual to be susceptible to expressing the phenotype. The disease is not expressed in heterozygous condition. Example: Cystic fibrosis is an autosomal recessive disease. A person who has only one recessive gene is said to be a \"carrier\" for the trait or disease, but they do not have any health problems from \"carrying\" one copy of the gene. The disease phenotype is expressed he/she inherits both the copies of the disease allele. The recessive disorders are typically not seen in every generation of an affected family. Other examples are Sickle cell anemia and Tay sachs disease Solution Answer: In Recessive mutations two copies of a disease allele are required for an individual to be susceptible to expressing the phenotype. The disease is not expressed in heterozygous condition. Example: Cystic fibrosis is an autosomal recessive disease. A person who has only one recessive gene is said to be a \"carrier\" for the trait or disease, but they do not have any health problems from \"carrying\" one copy of the gene. The disease phenotype is expressed he/she inherits both the copies of the disease allele. The recessive disorders are typically not seen in every generation of an affected family. Other examples are Sickle cell anemia and Tay sachs disease.