Genetics and the rule of probability (how to calculate progeny genetype)

The probability of one event, X, and another event, Y is the product of the probabilities of events X and Y. This is the multiplication rule, and in symbols it can be written as: P(X and Y) = P(X) · P(Y). The probability of one event, X, or another event, Y is the sum of the probabilities of events X and Y. This is the addition rule, and in symbols it can be written as: P(X or Y) = P(X) P(Y). The rules of probability theory can be applied to Mendelian genetics, in order to determine the likelihood of two parents creating an offspring with a particular phenotype. TERMS multiplication rule The multiplication rule states that the probability of two independent events, A and B, occurring together is equal to the probability of event A multiplied by the probability of event B. PROBABILITY AND SIMPLE MENDELIAN GENETICS When you flip a fair coin, there is a 1/2 chance it will land heads up and a 1/2 chance it will land tails up. Similarly, when an individual is heterozygous at a gene locus (Rr), there is a 1/2 chance a gamete will have the R allele and a 1/2 chance it will get the r allele. To determine the genotype at a given locus from parents of known genotypes, the basic rules of probability (multiplication and addition) are employed (Figure 1). MULTIPLICATION RULE The multiplication rule estimates the probability that two independent events, x and y, will occur together. To calculate the probability of the events occuring together, multiply the probabilities of each event. For example, if two Rr individuals mate, the chance that they have an rr offspring is the same as the chance the female gamete is r (1/2) times the chance that the male gamete is r (1/2): 1/2 x 1/2 = 1/4. Perhaps a couple wants to know the probability that all of their three planned children will be boys. Because mating of egg and sperm is an independent event, there is a 1/2 chance that each child will be a boy. The probabilities of each event are multiplied: ½ x ½ x ½ = 1/8, so there is a 1/8 chance that all three children will be boys. If the couple already has one boy and wants to know the probability of having two more, then the probability will be ½ x ½ = ¼, or 25%. #genotypes #geneticInformation #probabilityOfOneEvent #Allele #nucleicAcid #chromosome #geneticCode #genetics #genotype #GeneticsLecture #Heterozygous #Genetics101 #genetic #phenotype #GeneticExamQuestionsSolutions #pcr #Haploid #multiplicationRule #DNA #locus #mendelianGenetics #genes #productOfTheProbabilities #geneExpression #inheritance #probability #probabilityProblems #NikolaysGeneticsLessons #statistics #ruleOfProbability #productRule