1. Bellwork: 4/9 Put your phone up 
Week 4/8 - 4/12
Create your own punnett square problem & solve it

2. Today:
Bellwork
Part 3 Notes
Dihybrid Practice

3. Materials
Unit Book
Dihybrid Practice Worksheet

4. This Week: Monday: PS Quiz & Assign Project
Tues/Wed: Pt. 3 Notes & Practice
Thursday: Dihybrid Practice & Pt. 4 Notes
Friday: Blood Type Practice & Pt. 5 Notes

5. Homework Dihybrid Practice Genetic Illness Sign-Up Genetics Project
Due Thursday
Genetic Illness Sign-Up
Due Friday 4/12
Genetics Project
Due 4/24 at 11:59pm

6. Unit VI: Mendelian Genetics

7. Part III: Dihybrid Crosses

8. Review ?s What was Mendel’s first law of inheritance?
How is his first law related to meiosis?

9. Monohybrid Crosses
Involves the transmission of a single trait

10. Next ? Mendel Asked
Would the possession of one particular trait (e.g. seed shape) influence the segregation of another trait (e.g. seed color) or would they segregate independently?

11. Dihybrid Crosses
Mendel examined simultaneous inheritance of two traits
The 2 traits he examined…
Seed Shape – Round (R, dominant) versus wrinkled (r, recessive)
Seed Color – Yellow (Y, dominant) versus green (y, recessive)

12. THINK!
What distinguishes a monohybrid cross from a dihybrid cross?

13. Developed 2 Hypotheses Hypothesis 1: Two traits segregate together
Hypothesis 2: Two traits segregate independently

14. Hypothesis 1 Round (R) always goes with yellow (Y)
Wrinkled (r) always goes with green (y)
Predicted results from Punnett Square
3 round yellow:1 wrinkled green

15. Hypothesis 1I
Based on this hypothesis there are 4 possible gamete combinations
RY, Ry, rY, ry
Cross RrYy X RrYy
Predicted Results:
9 Round, Yellow: 3 wrinkled, Yellow:
3 Round, green: 1 wrinkled, green

16. Punnett Square

17. 2nd Law of Inheritance Law of Independent Assortment Why
Each allele pair on non-homologous chromosomes segregates independently of other gene pairs during gamete formation
Why
Because non-homologous chromosomes line up randomly in the center of the cell & are pulled to different poles
How they assort determines the homologous chromosomes (maternal vs paternal) the gamete possesses.

18. THINK!
Explain the difference between homologous & non-homologous chromosomes.

20. Solving Dihybrid PS Dihybrid Crosses Determine genotype of parents
Determine possible gamete combinations for each parent
determined by the equation 2n where n = number of heterozygotes
If n = 0, RRyy, then 2o = 1, only one possible gamete combination Ry
If n=1, Rryy, then 21 = 2, two possible gamete combination Ry, ry
If n=2, RrYy then 22= 4, four possible gamete combinations RY, Ry, rY, ry
Set up Punnett square
Fill in squares by combining allele from sperm and egg
Answer the question

21. Sample Problem!
In tomatoes, red fruit (R) is dominant over yellow fruit (r) and tallness (T) is dominant over shortness (t). A plant that is RrTT is crossed with a plant that is rrTt. What are the chances of an offspring being heterozygous for both traits?