Understanding Mendelian Genetics: Dominant & Recessive Alleles in Pea Plants

1. 10.2 Mendelian Genetics • Main Idea: Mendel explained how a dominant allele can mask the presence of a recessive allele

2. Pea Plants • Mendel chose the pea plant for several reasons • It is true breeding • Pea plants reproduce by self-fertilization • Can be easily cross pollinated by hand

3. Inheritance of traits • Mendel crossed a true breeding green seed plant with a true breeding yellow seed plant • This is the parent or P generation

4. F1 generation • All of the offspring from the P generation had yellow seeds • This is called the first filial or F1 generation • Mendel allowed this generation to self fertilize

5. F2 Generation • The F1 generation produced offspring with 1 green seed plant for every 3 yellow seed plants • That is a ratio of 3:1, Yellow to Green • This is the second filial or F2 generation

6. Mendel’s Traits • Mendel studied 7 traits and concluded there must be 2 forms for each trait • Allele-an alternate form of a single gene passed from generation to generation • Ex yellow or green seeds

7. Mendel’s traits • Mendel believed that each trait had a dominant and a recessive form • Dominant-the form of the trait that appeared in the F1 generation • Recessive-the form of the trait that was masked in the F1 generation

8. Dominance • The dominant allele is represented by a capital letter, the recessive by a lowercase letter • Ex Yellow = Y Green = y

9. alleles • Homozygous –2 of the same alleles for a trait • Ex. YY, yy • Heterozygous –2 different alleles for a trait • Ex. Yy • Genotype- The organisms allele pairs • Ex. YY, Yy, yy • Phenotype-The observable trait • Ex. Green or Yellow

10. Mendel’s Law of Segregation • The two alleles for each trait separate during meiosis • During fertilization 2 alleles unite randomly • A hybrid is an organism with a heterozygous genotype