1. Ch4 Sec1
Mendel’s Work

2. Key Concepts
What were the results of Mendel’s experiments, or crosses?
What controls the inheritance of traits in organisms?

3. Key Terms Heredity Trait Genetics Fertilization Purebred Gene Alleles
Dominant allele
Recessive allele
Hybrid

4. Ch4 Sec1 Mendel’s Experiment
Heredity is the passing of physical characteristics from parents to offspring
Trait is different characteristics such as height or seed color
Genetics is the scientific study of heredity
Fertilization is the joining of egg and sperm
Purebred organism is the offspring of many generations that have the same trait

5. Ch4 Sec1 Crossing Pea Plants The F1 Offspring The F2 Offspring
Experiments with Other Traits
In all of Mendel’s crosses, only one form of the trait appeared in the F1 generation. However, in the F2 generation, the “lost” form of the trait always reappeared in about one fourth of the plants

6. Ch4 Sec1 Dominant and Recessive Alleles Genes and Alleles
Gene for the factors that control a trait
Alleles are the different forms of a gene
An organism’s traits are controlled by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive
Dominant allele is one whose trait always shows up in the organism when the allele is present
Recessive allele is hidden whenever the dominant allele is present

7. Ch4 Sec1 Dominant and Recessive Alleles Alleles in Mendel’s Crosses
Hybrid organism has two different alleles for a trait
Symbols for Alleles
Significance of Mendel’s Contribution