1. What did Mendel Observe? How do alleles affect inheritance?
What Is Heredity?
What did Mendel Observe?
How do alleles affect inheritance?

2. Heredity
The passing of physical characteristics, or traits from parents to offspring.

3. VOCABULARY
Genetics: The study of Heredity (passing of traits from parent to offspring)
Fertilization: When a sperm and egg cell join to being forming a new organism.
Allele: Different forms of a gene
Purebred: Offspring that show the same forms of a trait
Hybrid: Two different alleles for a trait

4. Significance of Mendel's contribution
Before Mendel most people thought that traits were a blend of the parents’.
Mendel showed that offspring traits are determined by individual, separate alleles inherited from each parent.

5. Mendel’s experiments Tall and short pea plants
Dominant (Tall) and recessive (short) alleles
TT dominate homozygous
tt recessive homozygous
Tt Heterozygous
Discovery Education video:
Mendelian Genetics

6. The F1 and F2 offspring Purebred parental called “P” generation
Resulting offspring called “filial” or “F1” generation
Filial means “daughter” or “son”
In Mendel's crosses, some forms of a trait were hidden in one generation but reappeared in the next
P. 416: Draw and label the offspring in the F2 generation
Did the short trait disappear?
About ¾ were tall while the fourth was short

7. Experiments with other traits
Mendel continued his research and found that:
In all of his crosses, that 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 ¼ of the plants.

8. In an offspring having two recessive alleles
Alleles in Pea Plants P. 417
Mendel studied the inheritance of seven different traits in pea plants.
Circle the picture of the dominant allele in the P generation for each trait.
Under what conditions would the recessive form of one of these traits reappear?
In an offspring having two recessive alleles

9. Dominant and Recessive Alleles P. 418
What are the symbols and descriptions of allele? Use the word bank to complete the statements. What are the two possible ways the F2 offspring could look? T t
Tall
dominant t
recessive
Hybrid
dominant
dominant
recessive
recessive