Probability of Inheritance Lesson 3

1. Probability of InheritanceLesson 3 Mrs. Anna Ward Seventh Grade Science James Martin MS

2. DO NOW!!!! In rats, gray fur is dominant over white fur. Complete a Monohybrid Cross to identify the possible fur colors of offspring between a rat that is heterozygous for gray fur (Gg) with a rat that is homozygous recessive (gg) for white fur. In addtion, give the ratios of gray fur to white fur.

3. G=Gray fur Dominantg=white fur recessiveGg x gg1 Gg to 3 gg1 gray rat to 3 gray ratsor 25 % gray75 white DO NOW!!! Solution G g g g

4. Quiz today to check for understanding Announcements

5. Short video review on Punnett Squares • Quiz • Calculating Ratios from Punnett Squares • Independent Practice • Ink Think Article “Genes tell old Story” Agenda

6. http://www.youtube.com/watch?v=d4izVAkhMPQ REVIEW FROM YESTERDAY:PUNNETT SQUARES

7. In humans, brown eyes (B) are dominant to blue eyes (b). • What are the possible phenotypes for eye color as listed above? • What would the be genotype of: • a homozygous dominant human? • A homozygous recessive human? • A heterozygous human? • Which genotype(s) would code for brown eyes? • Which genotype(s) would code for blue eyes? • Draw a Punnett Square that crosses a homozygous dominant woman with a heterozygous man. • What are the possible genotypes? • Draw a Punnett Square that crosses a heterozygous female with a homozygous recessive male. • What are the possible genotypes? Quiz

8. For Monohybrid Crosses, the ratios are always going to occur in fourths, because there are four squares. • To Calculate the GENOTYPIC RATIOS, count the number of each GENOTYPE and put that over 4. • Example: The Genotypic Ratio in the figure to the right is: 1 BB to 2 Bb to 1 bb or 1:2:1 Calculating Ratios from Punnett Squares

9. To Calculate the PHENOTYPIC RATIOS, count the number of each PHENOTYPE and put that over 4. • There are typically only two phenotypes for monohybrid crosses, the dominant & the recessive trait. • Example: The Phenotypic Ratio in the figure to the right is: 3 Brown to 1 Blue or 3:1 Calculating Ratios from Punnett Squares

10. This is something you should be very familiar with from MATH class. • For monohybrid crosses, it is always going to be a factor of 25%, because there are 4 squares. • You can calculate the percentages based on the phenotype or genotype. • Example: • The genotype is 25% BB, 50% Bb, and 25% bb. • The phenotype is 75% brown, 25% blue. Calculating Percentages from Ratios

11. Now you try! Question # 1 In Rabbits, Black Fur (F) is dominant to White Fur (f). Imagine you have a Homozygous Dominant Black Male Rabbit that you are going to mate with a Homozygous Recessive White Female Rabbit. Draw the Punnett Square to predict the offspring. What is the genotype ratio? What is the phenotype ratio? Genotype Ratio: 100 % Heterozygous or Bb Phenotype Ratio: 100 % Black Fur

12. Now you try! Question # 2 In Rabbits, Black Fur (F) is dominant to White Fur (f). Imagine you have a Heterozygous Black Male Rabbit that you are going to mate with a Homozygous Recessive White Female Rabbit. Draw the Punnett Square to predict the offspring. What is the genotype ratio? What is the phenotype ratio? Genotype Ratio: 50% Heterozygous (Bb) Rabbits to 50% Homozygous Recessive Rabbits (bb) Phenotype Ratio: 50% Black Rabbits, 50% White Rabbits

13. Independent PracticeSheets

14. Remember this from last week? • Underline or highlight things you want to remember or you deem important • Circle words you don’t know • ? Mark thinks you don’t understand • Attach the Passage in your Science Notebook. INK THINK:“Old Genes Tell the Story”

15. In Rabbits, Black Fur (F) is dominant to White Fur (f). Imagine you have a Heterozygous Black Male Rabbit that you are going to mate with a Heterozygous Black Female Rabbit. • Draw the Punnett Square to predict the offspring. • What is the genotype ratio? • What is the phenotype ratio? EXIT TICKET OUT THE DOOR My sister’s bunny, Basil Q. Hoppenfluff