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. 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 F 1 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 http://anthro.palomar.edu/mendel/quizzes/ mendqui1.htm