What is the probability to have 3 children in a sequence: Boy, Girl, Boy?

These deal with probabilities of independent events. If the probabilities are joined by OR, then add the individual probabilities; if they are joined by AND, the multiply the probabilities. Inheriting blood type and Rh factor are independent of each other. If the probability of having blood type A is 25% and the probability of being Rh is 50%, then the probability of being A or Rh is 75%. The probability of being both is 12.5%. Additive genetic effects Additive genetic effects consist of the effects of two or more alleles of different loci combined in such a way that the sum of their effects in unison is equal to the sum of their effects individually. Such phenomena are only possible when the alles involved do not interact with one another in such a way that would modify, hinder, or amplify the effects of any one gene involved. An additive genetic effect is a form of quantitative inheritance as the effects of the combined genes can be simply added together. Additive genetic effects are different from cumulative gene action because in the last, the effects of the genes combined create an action of increased intensity. Rule of sum In combinatorics, the rule of sum or addition principle is a basic counting principle. Stated simply, it is the idea that if we have a ways of doing something and b ways of doing another thing and we can not do both at the same time, then there are a   b ways to choose one of the actions. More formally, the rule of sum is a fact about set theory. It states that sum of the sizes of a finite collection of pairwise disjoint sets is the size of the union of these sets. That is, if S_{1}, S_{2},..., S_{n} are pairwise disjoint sets, then we have: |S_{1}| |S_{2}| \cdots |S_{n}| = |S_{1} \cup S_{2} \cup \cdots \cup S_{n}| Simple example A woman has decided to shop at one store today, either in the north part of town or the south part of town. If she visits the north part of town, she will either shop at a mall, a furniture store, or a jewelry store (3 ways). If she visits the south part of town then she will either shop at a clothing store or a shoe store (2 ways). Thus there are 3 2=5 possible shops the woman could end up shopping at today. Inclusion-exclusion principle The inclusion-exclusion principle can be thought of as a generalization of the rule of sum in that it too enumerates the number of elements in the union of some sets (but does not require the sets to be disjoint). It states that if A1, ..., Anare finite sets, then #genes #GeneticsLecture #multiplyTheProbabilities #independentEvents #GeneticExamQuestionsSolutions #AdditiveGeneticEffects #probability #geneExpression #gene #chromosome #geneticCode #Genetics101 #genetics #ruleOfSum #quantitativeInheritance #genotype #DNA #individualProbabilities