Ch.14: Probability and Advanced Genetics
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Mendel’s laws of segregation and independent assortment reflect the rules of probability
When tossing a coin, the outcome of one toss has no impact on the outcome of the next toss
In the same way, the alleles of one gene segregate into gametes independently of another gene’s
alleles
Rules of addition and multiplication:
Multiplication
• The multiplication rule states that the probability that two or more ______________________
events will occur together is the product of their individual probabilities (the rule of “_______”)
• Rule of multiplication is that the probability that independent events will occur _________________
is the _________________ of their individual probabilities. For example:
• Question:
• In a Mendelian cross between pea plants that are heterozygous for flower color (Pp), what is the
probability that the offspring will be homozygous recessive?
• Answer:
• Probability that an egg from the F1 (Pp) will receive a p allele =
• Probability that a sperm from the F1 (Pp) will receive a p allele =
• The overall probability that two recessive alleles will unite, one from the egg _____one from the
sperm, simultaneously, at fertilization is:
Addition
• Under the rule of addition, the probability of an event that can occur two or more __________
ways is the sum of the separate probabilities of those ways (the rule of “_____”).
• The rule of addition can be used to figure out the probability that an F2 plant from a monohybrid
cross will be heterozygous rather than homozygous
• Question:
• In a Mendelian cross between pea plants that are heterozygous for flower color (Pp), what is the
probability of the offspring being a heterozygote?
• Answer:
• There are two ways in which a heterozygote may be produced: the dominant allele (P) may be in the
egg and the recessive allele (p) in the sperm, ____the dominant allele may be in the sperm and the
recessive in the egg. Consequently, the probability that the offspring will be heterozygous is the sum
of the probabilities of those two possible ways:
• Probability that the dominant allele will be in the egg with the recessive in the sperm is ___________
• Probability that the dominant allele will be in the sperm and the recessive in the egg is ____________
• Therefore, the probability that a heterozygous offspring will be produced is ____________________
Solving Complex genetics problems:
• We can apply the multiplication and addition rules to predict the outcome of crosses involving
multiple characters
• A dihybrid or other multicharacter cross is equivalent to two or more __________________
monohybrid crosses occurring simultaneously
• In calculating the chances for various genotypes, __________________________ is considered
separately, and then the ________________________________ are _________________ together
Probability Question page 259