1. Introduction to Genetics
Chapter 11

2. The Work of Gregor Mendel
Q: Does anybody know who this man is? A: Gregor Mendel
Q: What did he do? A: father of genetics, used garden peas to study inheritance.
Section 11.1

3. The Experiments of Mendel
Heredity is the delivery of characteristics from parent to offspring.
Scientific study of heredity is genetics.
Austrian monk Gregor Mendel is the father of genetics.
Used pea plants (a model system)

4. The Experiments of Mendel
The Role of Fertilization
Fertilization is when male/female reproductive cells join to make a new cell.
Pea plants normally self pollinate “true breeding”
Offspring identical
Each plant had certain traits.
These traits may vary between individuals.
Q: What are male and female reproductive cells called? A: Sperm and Egg
Q: How can self pollination occur? A: When an organism, say a plant, has both male and female parts. Sexual reproduction with only one parent.
Q: What would be some examples of varying traits? A: short/tall, yellow/green, wrinkled/smooth

5. The Experiments of Mendel
Mendel crossed his “true breeding” plants to see how traits would be expressed.
He studied 7 different traits.
Each had two contrasting characters.
Offspring of a cross between different parents are called hybrids.
***This crossing was done by cutting off the pollen “male” parts, and dusting with male parts from another plant (now called cross pollination)
Q: Can anyone name an example of another hybrid animal/plant.

6. The Experiments of Mendel
Genes and Alleles
Each original pair of plants is the P generation.
Offspring are F1 = first filial
Genes are the factors (traits) passed from one generation to the next.
Alleles are alternative forms of a gene.
Q: What does the P stand for ? A: parental
Q: Give an example of an allele? A: Short/Tall

7. The Experiments of Mendel
Dominant and Recessive Alleles
Principle of Dominance (Mendel’s 2nd Conclusion)
Dominant: trait will show if one allele present (masks other allele)
Recessive: need two alleles for trait to appear

8. Segregation Mendel didn’t stop with crossing the parent plants.
He thought: Where did the recessive alleles go?
He allowed all 7 kinds of plants to self pollinate.
Called these the F2

9. Segregation The F1 Cross The F2 plants showed the recessive alleles!
¼ of the plants showed this trait.
How could this be?
At some point, the recessive allele had separated from the dominant.
Another word for separation=SEGREGATION
Alleles segregate during the formation of gametes.

10. Segregation
During gamete formation, the alleles for each gene segregate.
Each gamete carries only one allele for each gene.