The Work of Gregor Mendel

1. The Work of Gregor Mendel

2. Think About It! • What is an inheritance? • It is something we each receive from our parents – a contribution that determines blood type, hair color, and much more. • Every living thing has a set of characteristics that are inherited from its parent or parents. • Heredity is the delivery of characteristics from parent to offspring.

3. Think About It! • Genetics is the scientific study of heredity. • It is the key to understanding what makes each organism unique. • Was founded by an Austrian monk named Gregor Mendel.

4. Experiments of Gregor Mendel • Mendel • Performed his work in a monastery garden. • Carried out his work with ordinary garden peas, because peas are small and easy to grow. • These peas represented a “model system”

5. Experiments of Gregor Mendel • Mendel was able to carry out experiments that would have been impossible or taken years to do.

6. Experiments of Gregor Mendel • Studied seven different pea plant traits. Each trait had two contrasting characteristics.

7. Pea Plant Traits, Contd.

8. The Role of Fertilization • Fertilization is a process that produces a new cell when male and female reproductive cells join. • Male reproductive cells are called sperm. • Female reproductive cells are called eggs.

9. The Role of Fertilization • In seed plants, fertilization occurs through self- or cross-pollination. • Pollination transfers pollen (sperm) from the male reproductive organ to the female reproductive organ (stigma).

10. The Role of Fertilization • In self-pollination, sperm cells fertilize eggs cells from within the same flower. • Peas flowers are self-pollinating, because of this they • Produce a seed that inherits all of the characteristics (traits) of its parents. • Are “true breeding” because they produce offspring with identical traits.

11. The Role of Fertilization • In cross-pollination, pollen from the anther of a flower goes to the stigma of a different flower. • Mendel utilized this process to learn more about traits. • A trait is a specific characteristic of an individual that may vary from one individual to another.

12. The Role of Fertilization (Cross-Pollination, Continued) First, Mendel prevented self-pollination by removing the male part of a flower. Then, Mendel dusted the female part of the flower with pollen from a different plant. These plants produced a seed that inherited different characteristics of its parent. The offspring of these plants are called hybrids.

13. Mendel’s Conclusions • An individuals characteristics are determined by genes that are passed from parent to offspring. • Genes are segments of DNA that determine a trait.

14. Mendel’s Conclusions • Each individual has two factors for each trait, one from each parent. • Alleles are forms of a gene for a specific trait. • They are a single member of a pair of genes, responsible for a single trait.

15. Mendel’s Conclusions • Some alleles are dominant and others are recessive. • This is called the principle of dominance.

16. Mendel’s Conclusions • An organism with one dominant allele for a particular trait will exhibit the trait. • A dominant allele is represented by a capital letter. • An organism with a recessive allele for a particular trait will exhibit the trait when the dominant allele is not present. • A recessive allele is represented by a lowercase letter.

17. Segregation • Mendel assumed that • A dominant allele masks a recessive allele in an F1 generation.

18. Segregation • In F2 generations the recessive trait reappeared indicating that the dominant and recessive alleles had separated. - Segregation explains how this occurred.

19. Segregation • Is the separation of alleles during gamete formation. • Gametes are sex cells • When gametes are formed, allele pairs separate leaving each cell with a single allele for each trait. • When fertilization occurs alleles randomly unite to form a gene for a specific trait

20. Practice Quiz for Mendel's Genetics • http://anthro.palomar.edu/mendel/quizzes/mendqui1.htm