Page 134 - Science Course 3 (Book 1)

Mo4-L1b: What is the Conclusion of Mendel’s Experiment?

Let’s Begin First-Generation Crosses

Genotype AA Aa aa
Mendel’s Results
Once Mendel had enough true-breeding plants for a
trait he wanted to test, he cross-pollinated selected Phenotype A:
plants. dominant/a
recessive
Plants are called hybrids if they come from true-
breeding parent plants with different forms of the
same trait.
Phenotype
A and a
co-dominant

Second-Generation (Hybrid) Crosses

Purple X Purple
(Hybrid) (Hybrid) Genotype AA Aa aa

Phenotype A:
dominant/a
Purple and White offspring recessive

Phenotype
A and a
co-dominant

Mendel’s Results

Mendel recorded traits of offspring from many hybrid
crosses.

Mendel also cross-pollinated hybrid plants.

He observed that offspring of hybrid crosses always
showed traits in a 3:1 ratio.
Tomatoes Cherry Tomatoes
RR rr
Mendel’s Conclusions

A dominant trait is a genetic factor that blocks
Rr Rr another genetic factor.
X A recessive trait is a genetic factor that is blocked

Rr Rr by the presence of a dominant factor.

RR Rr rR rr
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