1. The Punnett Square Approach and Probability
Studying Heredity
The Punnett Square Approach and Probability

2. Will individuals with different genotypes have different phenotypes?
Maybe?
Genotype: T T Phenotype: Tall
Genotype: T t Phenotype: Tall
Can individuals with different phenotypes have the same genotype?
No?
Phenotype: Tall Genotype: TT or Tt Phenotype: Short Genotype: tt

3. Punnett Squares
In the early 1900s, Dr. Reginald Punnett developed a square to predict possible offspring of a cross between two known genotypes.
Punnett squares are useful for keeping
track in a cross.

4. P1 Monohybrid Cross r r Rr Rr R R Rr Rr Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Wrinkled seeds
RR x rr r r
Genotype:
Phenotype:
Genotypic Ratio:
Phenotypic Ratio: Rr
Round
All alike
All Round Rr Rr R R Rr Rr

5. P1 Monohybrid Cross Review
Homozygous dominant x Homozygous recessive
Offspring all Heterozygous (hybrids)
Offspring called F1 generation
Genotypic & Phenotypic ratio is ALL ALIKE

6. F1 Monohybrid Cross R r RR Rr R r Rr rr Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Round seeds
Rr x Rr R r
Genotype:
Phenotype:
G. Ratio:
P. Ratio:
RR, Rr, rr
Round &
wrinkled
1:2:1
3:1 RR Rr R r Rr rr

7. F1 Monohybrid Cross Review
Heterozygous x heterozygous
Offspring: 25% Homozygous dominant RR 50% Heterozygous Rr 25% Homozygous Recessive rr
Offspring called F2 generation
Genotypic ratio is 1:2:1
Phenotypic Ratio is 3:1

8. F2 Monohybrid Cross (1st)
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Round seeds
RR x Rr R r
Genotype:
Phenotype:
G. Ratio:
P. Ratio:
RR, Rr,
Round
100% Round RR Rr R R RR Rr

9. F2 Monohybrid Cross (2nd)
Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Wrinkled seeds
Rr x rr r r
Genotype:
Phenotype:
G. Ratio:
P. Ratio:
RR, Rr,
Round &
Wrinkled
1:1 Rr Rr R r rr rr

10. F2 Monohybrid Cross Review
Homozygous x heterozygous(hybrid)
Offspring: 50% Homozygous RR or rr 50% Heterozygous Rr
Phenotypic Ratio is 1:1
Called Test Cross because the offspring have SAME genotype as parents

11. Did You
Learn
Anything

12. See if you can determine the parental genotypes based on the offspring in the Punnett square below.? ? ? Bb Bb ? bb bb

13. In Mendel’s original experiment with purple and white pea flowers, why are only purple flowers seen in the F1 generation, but both purple and white flowers found in the next (F2) generation? P1 F1 F2
&

14. The trait that disappears
Complete the Bridge Map below
The observed trait
Dominant
Recessive
The trait that disappears

15. The way an organism looks
Complete the Bridge Map below
The way an organism looks
Phenotype
Genotype
Allele Combination

16. check up
neck up
from the