Probability & Punnett Squares

Probability A concept that can be used to predict the results of a particular event Examples Chance of a specific team winning a sporting event Chance of a coin landing on heads in a coin toss Predict what is likely to occur, not necessarily what will actually occur

Probability and Punnett Squares Punnett Square – A chart that shows how parents’ alleles might combine in an offspring a tool that can help you understand the patterns of heredity Geneticists use Punnett Squares to show all the possible outcomes of a genetic cross and to determine the probability of a particular outcome Punnett Squares Explained at http://www.siskiyous.edu/class/bio1/genetics/monohybrid_v2.html

Probability and Punnett Squares What is the probabilty of….. The offspring having a yellow seed color? 2 in 4 The offspring having a green seed color?

Probability and Punnett Squares How else can probability be written? The offspring having a yellow seed color? 2 in 4 or 50% The offspring having a green seed color?

Using a Punnett Square In rabbits, black fur color is dominant to white. What is the probability of producing a white rabbit if two heterozygous rabbits mate?

Let’s Practice In pine trees, long needles are dominant over short needles. Cross a homozygous dominant plant with a plant that is heterozygous. What is the probability that the parents will produce offspring that have short needles? Give the genotypic and phenotypic ratios.

Let’s Practice 2. In cats, a striped coat is dominant over a solid coat. Cross a cat with a solid coat with a cat that is heterozygous for a striped coat. What is the probability that the parents will produce offspring with a solid coat? Give the genotypic and phenotypic ratios.

Let’s Practice 3. In humans, dark hair is dominant over light hair. Cross a man that is homozygous recessive with a woman that is homozygous dominant. What is the probability that the parents will produce offspring with light hair? Give the genotypic and phenotypic ratios.