1. Mendel’s Peas Unit 18: Genetics Assignment 3: Inheritance
Dihybrid Inheritance
Mendel’s Peas
Unit 18: Genetics
Assignment 3: Inheritance

2. Starter Activity 1 Define the following terms: Allele Heterozygous
Homozygous

3. Starter Activity 2 Bb LL ff Gg Tt WW Ww Which of these genotypes are
Heterozygous
Homozygous
Bb LL ff Gg Tt WW Ww

4. Starter Activity 3
a) Construct a Punnett square for the following genetic cross:
Parent 1: Red Petals Parent 2: Pink Petals
Rr X rr
b) What proportion of the offspring will have
Red petals?
Pink Petals

5. Follow up question:
If the plant produced 50 offspring, how many would you expect to have
Red petals
Pink petals.
In nature, do you think this would be the case?
What if it produced offspring, would the outcomes be closer to the expected? Why?

6. Dihybrid Inheritance
The inheritance of two related traits. e.g. The height of a plant and its petal colours T = Tall t = short R = Red r = pink We can write genomes like this: TtRr or TTRR

7. Punnett Square F1 Generation:
Parent 1) TTRR Parent 2) ttrr TR tr

8. Punnett Square F1 Generation:
Parent 1) TTRR Parent 2) ttrr TR tr
TtTr 
 TtTr

9. 100 % Offspring have the Genotype: TtRr What is their Phenotype
100 % Offspring have the Genotype: TtRr What is their Phenotype? Tall, Red Construct a Punnett square for the F2 Generation:

10. Parent 1) TtRr Parent 2) TtRrTR Tr tR tr

11. Parent 1) TtRr Parent 2) TtRrTR Tr tR tr
TTRR 
 TTRr
TtRR 
TtRr 
 TTrr
 TtRr
Ttrr 
ttRR 
ttRr 
 Ttrr
 ttrr

12. 9:3:3:1 ratio
Red, Tall = 9 Red, Short = 3 Pink, Tall = 3 Pink, Short = 1

13. Who Was Gregor Mendel?
Pea experiments
Inheritance

14. Class Work
Complete the worksheet applying the principles we have covered with tall/short, red/pink flowers to the example of Mendel’s pea plants.

15. Video:

16. Plenary Activity: Cats!
B = Grey b = ginger S = Dark stripes s = no stripes Write out all possible genotypes / phenotypes:

17. Answers:
You could have: BbSs, BBSS = Grey, Stripes BBss, Bbss = Grey, no Stripes bbSs, bbSS = ginger, stripes bbss = ginger no stripes