Allele Version of a gene Wild type allele Intact fully functional copy version of a gene Null allele Non functional type of allele Cystic Fibrosis Recessive disorder Probability Number of times an event occurs total number of events Random sampling error Large for small samples Small for large samples Sum Rule Probability that one or the other of two mutually exclusive outcomes will occur is the sum of their respective probabilities 1 6 1 6 1 3 According to the National Safety Council In US 14 chance of dying of cancer 17 chance of dying of heart disease o Therefore assuming nobody dies of both you have a 14 17 31 chance of dying of either cancer or heart disease Dihybrid cross w sum rule Two genes produce 9 3 3 1 o Gene 1 Affects Ears De normal allele de droopy ears o Gene 2 Affects tail Ct Normal tail ct crinkly tail If two heterozygous De de Ct ct mice are crossed o The the predicted ratio of offspring is 9 normal ears normal tails 3 normal ears crinkly tails 3 droopy ears normal tails 1 droopy ears crinkly tail What is probability that an offspring of the above cross will have normal ears and normal tail droopy ears and crinkly tail o 9 16 1 16 10 16 or 9 1 16 10 16 Product Rule Just multiply o 1 4rr x 1 4Yy or whatever your combo is Product Rule involves independent events Congential analgesia o Recessive trait in humans Affected individuals do not perceive extreme sensations as painful