1 / 29

Probability & Punnett Squares

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

rendor
Download Presentation

Probability & Punnett Squares

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Probability & Punnett Squares

  2. 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

  3. Probability and Heredity • Think back to Mendel’s plant experiments • He noticed that traits were inherited in patterns • For example, when he crossed two plants that were heterozygous for stem height (Tt) he noticed their offspring would inherit this trait in a predictable pattern, with 3 out of 4 having tall stem height.

  4. Probability and Heredity • Each time Mendel repeated the cross, he would obtain similar results • He could say that the probability, or chance, of the cross producing a tall plant was 3 in 4 and the probability of producing a short plant was 1 in 4.

  5. Mendel noticed the same pattern of inheritance in other traits as well

  6. 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

  7. 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? 2 in 4

  8. 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? 2 in 4 or 50%

  9. 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?

  10. Using a Punnett Square • Step 1: figure out the genotype of the parents. • Black is dominant to white. • B - black • b - white • Parents are heterozygous. • Bb - dad • Bb - mom

  11. Using a Punnett Square Bb Bb • Step 2: set up a Punnett Square. B b B b

  12. Using a Punnett Square • Step 3: Fill in the Punnett Square. B b B b

  13. Using a Punnett Square • Step 3: Fill in the Punnett Square. B b BB B b

  14. Using a Punnett Square • Step 3: Fill in the Punnett Square. B b BB Bb B b

  15. Using a Punnett Square • Step 3: Fill in the Punnett Square. B b BB Bb B Bb b

  16. Using a Punnett Square • Step 3: Fill in the Punnett Square. B b BB Bb B bb Bb b

  17. Step 4: Count the results. Genotypes 1 homozygous dominant Using a Punnett Square B b BB Bb B bb Bb b

  18. Step 4: Count the results. Genotypes 1 homozygous dominant 2 heterozygotes Using a Punnett Square B b BB Bb B bb Bb b

  19. Step 4: Count the results. Genotypes 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Using Punnett Square B b BB Bb B bb Bb b

  20. Step 4: Count the results. Genotypes 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Phenotypes Using a Punnett Square B b BB Bb B bb Bb b

  21. Step 4: Count the results. Genotypes 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Phenotypes 3 black fur Using a Punnett Square B b BB Bb B bb Bb b

  22. Step 4: Count the results. Genotypes 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Phenotypes 3 black fur 1 white fur Using a Punnett Square B b BB Bb B bb Bb b

  23. Probability and Punnett Squares • In rabbits, black fur color is dominant to white. What is the probability of producing a white rabbit if two heterozygous rabbits mate? • 1 in 4 or 25%

  24. Representing Ratios • Probability can also be represented in ratios • A ratio compares or shows the relationship between a part to the whole • Example the probability that a coin will land on heads in a single coin toss is 1 in 2 or 50% • As a ratio, the probability would be written as 1:2 and would be read as, “One to two.” • In genetics we use rations to represent probability

  25. Step 4: Count the results. Genotypes = 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Genotypic Ratio = 1:2:1 Phenotypes 3 black fur 1 white fur Using a Punnett Square B b BB Bb B bb Bb b

  26. Step 4: Count the results. Genotypes = 1 homozygous dominant 2 heterozygotes 1 homozygous recessive Genotypic Ratio = 1:2:1 Phenotypes 3 black fur 1 white fur Phenotypic Ratio = 3:1 Using a Punnett Square B b BB Bb B bb Bb b

  27. 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.

  28. 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.

  29. 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.

More Related