1. Ch.11-2b Independent Assortment

2. POINT > Define a dihybrid cross POINT > Describe Mendel’s dihybrid experiments POINT > Show how meiosis could lead to different allele combinations POINT > Use a Punnett square to predict genotypes and phenotypes from a dihybrid cross POINT > Define the Law of Independent Assortment

3. POINT > Define a dihybrid cross So far you have examined monohybrid crosses: crosses involving only one trait Mendel wondered if inheritance of one trait affected the inheritance of other traits, or if they all acted independently A dihybrid cross is a genetic cross that involves two traits Punnett squares are again useful in explaining what Mendel found

4. ? Ex. Mendel crossed plants purebred for yellow seeds and smooth seed coats with plants purebred for green seeds and wrinkled seed coats All the F 1 had yellow seeds and smooth seeds coats (YYRR)(yyrr) (YyRr) P F1F1 X POINT > Describe Mendel’s dihybrid experiments

5. ? First generation (F 1 ) plants self-pollinated: All trait combinations show up in the F 2 (YyRr) F1F1 F2F2 X POINT > Describe Mendel’s dihybrid experiments

6. F2F2 Every trait combination Mendel tried generated an F 2 with the same proportions: 9 : 3 : 3 : 1

7. WB CHECK: Which of the following is a monohybrid cross? a) Plant with black leaves X plant with pink flowers b) Plant with red berries and wrinkled seeds X plant with white berries and smooth seeds c) Fruit fly with 2 sets of wings X fruit fly with normal wings d) Fruit fly with white eyes and 8 legs X fruit fly with red eyes and 2 sets of wings

8. WB CHECK: Which of the following is a dihybrid cross? a) Plant with black leaves X plant with pink flowers b) Plant with red berries and wrinkled seeds X plant with white berries and smooth seeds c) Fruit fly with 2 sets of wings X fruit fly with normal wings d) Fruit fly with white eyes and 8 legs X fruit fly with red eyes and 2 sets of wings

9. YYyy RRrr RR YY yy rr R Y R Yy r y r POINT > Show how meiosis could lead to different allele combinations F 1 plant meiosis (YyRr)

10. YYyy RR rr YY rr yy RR y R y R Y r Y r POINT > Show how meiosis could lead to different allele combinations F 1 plant meiosis (YyRr)

11. Y r y RR Y y r YRyr Yr y R 25% Expected gametes if traits move independently of each other

12. A Punnett square to examine the inheritance of two different traits requires a 4x4 grid:

13. To generate gametes use FOIL: Each gamete must have only one letter from each trait!! Y y R r YRYryRyr R Y Y r y R y r

14. WB CHECK: Show the 4 possible gametes produced by a raccoon heterozygous for tail length (Tt) and heterozygous for ear tufts (Ee): TE Te tE te

15. YRYryRyr YR Yr yR yr YYRRYYRrYyRRYyRr YYRrYYrrYyRrYyrr YyRRYyRryyRRyyRr YyRrYyrryyRryyrr Each gamete must have only one letter from each trait!! POINT > Use a Punnett square to predict genotypes and phenotypes from a dihybrid cross

16. YRYryRyr YR Yr yR yr YYRRYYRrYyRRYyRr YYRrYYrrYyRrYyrr YyRRYyRryyRRyyRr YyRrYyrryyRryyrr Genotypes YYRR YYRr YYrr Yyrr YyRr yyrr yyRr YyRR yyRR 1 2 1 2 4 2 1 2 1 POINT > Use a Punnett square to predict genotypes and phenotypes from a dihybrid cross

17. YRYryRyr YR Yr yR yr YYRRYYRrYyRRYyRr YYRrYYrrYyRrYyrr YyRRYyRryyRRyyRr YyRrYyrryyRryyrr POINT > Use a Punnett square to predict genotypes and phenotypes from a dihybrid cross

18. YRYryRyr YR Yr yR yr Phenotypes Yellow, Round 9 Yellow, Wrinkled 3 Green, Round 3 Green, Wrinkled 1 POINT > Use a Punnett square to predict genotypes and phenotypes from a dihybrid cross

19. Law of Independent Assortment: Genes for different traits segregate independently during gamete formation (meiosis) Helps explain great amount of variation in many species

20. Read pages 313-318 Finish Assess p. 318 and any other missing homework Complete your Exam 1 Study Guide