Genetics Data and Probability SBI3UP

Mendelian genetics demonstrates the rules of probability The law of segregation and independent assortment are like tossing a coin or rolling dice. Tossing a coin = ½ chance of tossing heads Rolling dice = 1/6 chance of rolling a 2 and 5/6 chance of rolling another # Probability ranges from 0-1 (no chance to 100% chance)

The outcome of one toss has no impact on the outcome of the next Each toss is an independent event Like the distribution of alleles into gametes Each ovum from a heterozygous parent has a ½ chance of carrying the dominant allele and ½ chance of carrying the recessive allele Same for sperm

Rules of Probability: Rule of Multiplication Rule of Addition

Rule of Multiplication When to use: Used to determine probability that 2+ independent events will occur together in a specific combination How to use: Calculate probability of each independent event Multiply individual probabilities to get overall probability of events happening together

The probability that 2 coins tossed at the same time will land heads up is ½ x ½ = ¼ The probability that two heterogyzous pea plants (Pp) will produce a white-flowered offspring (pp) is ¼ ½ of gametes from each parent carry the “p” allele ½ x ½ = ¼ This is the same info we can get from drawing a Punnett square, but w/o having to draw a Punnet square.

Example 1: What is the probability of a heterozygous parent (YyRr) of producing a YR gamete? Example 2: For a cross between two parents with genotypes YyRr, what is the probability that the offspring will have a YYRR genotype.

Example 3: In a cross b/t AaBbCc x AaBBCC what is the probability that the offspring will be AaBbCC?

2. Rule of Addition: When to use: Used to determine the probability of an event occurring 2+ different ways How to use: Sum the probability of each different way

Example 4: If two heterozygous pea plants are crossed, what is the probability of the offspring being a heterozygote?

Example 5: In a cross b/t AaBbCc x AaBBCC what is the probability that the offspring will be AABbCc or AABBCC?