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

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

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

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.

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

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

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.

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

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