1. Colorado Agriscience Curriculum
Unit 4: Reproduction and Genetics Lesson 12: Dominant and Recessive Genes
Colorado Agriscience Curriculum

2. Unit 4, Lesson 12 Dominant and Recessive PP
I. Monohybrid Crosses
A. Three class genotypes
1. Homozygous Dominant = BB
2. Homozygous Recessive = bb
3. Heterozygous = Bb
B. B = Black & b = Red
C. Six possible crosses:
BB x BB, BB x Bb, BB x bb, Bb x Bb, Bb x bb, bb x bb
Unit 4, Lesson 12 Dominant and Recessive PP

3. Unit 4, Lesson 12 Dominant and Recessive PP
I. Predicting Ratio’s
Homozygous x Homozygous
A. Genotype
2. Results in a homozygous dominant zygote
B. BB x BB
Phenotype:
1. Each parent can only contribute a dominant gene B BB
Unit 4, Lesson 12 Dominant and Recessive PP

4. Unit 4, Lesson 12 Dominant and Recessive PP
I. Predicting Ratios
B. Homozygous x Homozygous
. bb x bb
All will be red
Genotypic Ratio
4bb : 0
Phenotypic Ratio
4 red coats : 0 black coats b bb
Unit 4, Lesson 12 Dominant and Recessive PP

5. I. Six Fundamentals Types of Mating
Homozygous x Homozygous
F. BB x bb
Genotypic ratio:
0BB : 4Bb
All offspring will be heterozygous
Phenotypic ratio: 4 black coat : 0 red coat B b Bb
Unit 4, Lesson 12 Dominant and Recessive PP

6. II. Predicting Ratios Homozymous x Heterozygous
E. BB x Bb
1. Genotypic Ratio
2 BB : 2 Bb
2. Phenotypic Ratio
a) 4 Black color B BB b Bb
Unit 4, Lesson 12 Dominant and Recessive PP

7. III. Predicting Ratio’s
G. Bb x Bb
1. Phenotypic Ratio
a) 3 black to 1 red or 3:1
2. Genotypic Ratio
a) 1BB: 2Bb: 1bb B b BB Bb bb
Unit 4, Lesson 12 Dominant and Recessive PP

8. Unit 4, Lesson 12 Dominant and Recessive PP
IV. Predicting Ratio
H. Bb x bb
1. Genotypic Ratio
a) 2Bb: 2bb
2. Phenotypic Ratio
a) 2 black to 2 red b B Bb bb
Unit 4, Lesson 12 Dominant and Recessive PP

9. Unit 4, Lesson 12 Dominant and Recessive PP
II. Multiple Gene Pairs
A. Mating
1. B = Black & b = Red
2. P = Polled & p = polled
B. Bull
1. BbPp
C. Cow
D. What will the phenotypic & genotypic ratios be?
Unit 4, Lesson 12 Dominant and Recessive PP

10. Unit 4, Lesson 12 Dominant and Recessive PP
II. Multiple Gene Pairs PB Pb pB pb
PPBB
PPBb
PpBB
PpBb
PPbb
Ppbb
ppBB
ppBb
ppbb
Unit 4, Lesson 12 Dominant and Recessive PP

11. Unit 4, Lesson 12 Dominant and Recessive PP
II. Multiple Gene Pairs
E. Genotypic Ratio
1. 1 PPBB: 2 PPBb: 1 PPbb: 2 PpBB: PpBb: 2 Ppbb: 2 ppBb: 1ppbb
F. Phenotype
1. 9 polled and black
2. 3 polled and red
3. 3 horned and black
4. 1 horned and red
Unit 4, Lesson 12 Dominant and Recessive PP

12. Unit 4, Lesson 12 Dominant and Recessive PP
Worksheet 1 B b B b B b B b
Unit 4, Lesson 12 Dominant and Recessive PP

13. Unit 4, Lesson 12 Dominant and Recessive PP
Worksheet 2 B b b
Unit 4, Lesson 12 Dominant and Recessive PP

14. Unit 4, Lesson 12 Dominant and Recessive PP
Worksheet 3 PB Pb pB pb
Unit 4, Lesson 12 Dominant and Recessive PP