Chapter 5.1 Mendel’s Work

1. Chapter 5.1 Mendel’s Work 7.2.d Students know plant and animal cells contain many thousands of different genes and typically have two copies of every gene. The two copies (or alleles) of the gene may or may not be identical, and one may be dominant in determining the phenotype while the other is recessive.

2. Mendel • Gregory Mendel was a priest in Europe who did an experiment with pea plants • Heredity- passing of traits from parent to offspring • Trait- form of a characteristic like height or seed color • Genetics- the study of heredity

3. Mendel’s Experiments • Fertilization- when the male and female sex cells join • Pollination- when pollen reaches the pistil • Purebred- same 2 alleles for a trait • P generation- Parental generation • Pea plants are self-pollinating • Self-pollinating- pollen lands on pistil of same flower

4. Crossing Pea Plants • Gregor Mendel crossed pea plants that had different traits. The illustrations show how he did this. Mendel crossed 2 plants by taking pollen from one flower and brushing it onto a flower of another plant

5. Mendel’s Experiments • F1 generation- Offspring from the P generation • F2 generation- Offspring from the F1 generation • Mendel crossed one short with one tall pea plant • All of F1 were tall and ¾ of the F2 were tall

6. Experiments With Other Traits Key concept: “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.”

7. Dominant and Recessive Alleles • Mendel demonstrated that factors control inheritance of traits • Those factors come in pairs: one from the female (mom) and one from the male (dad) • Gene- factors that control a trait • Alleles- different forms of the gene • Key concept: “An organism’s traits are determined by the alleles it inherits from its parents. Some alleles are dominant, while other alleles are recessive.”

8. Dominant and Recessive Alleles • Dominated allele- trait that always shows up in an organism when it is present (Tt, TT) • Recessive allele- trait that is hidden whenever the dominant allele is there (tt)

9. Dominant and Recessive Alleles • Hybrid- has 2 different alleles for a trait • Before Mendel people thought that traits were blended when there were 2 different traits which was incorrect • Traits are determined by individual alleles inherited from each parent • Capital letter represents dominate trait • Lowercase letter represents recessive trait • Because of Mendel’s work with genetics he has been called the Father of Genetics

10. Section 1: Mendel’s Work What were the results of Mendel’s experiments, or crosses? What controls the inheritance of traits in organisms?