CHAPTER 9 INTRO TO GENETICS

INTRODUCTION TO GENETICS

MENDEL Self Pollination vs. Cross Pollination

PURE PLANTS P = Parent generation F1 generation. –Offspring of a cross between parents F2 generation. –Offspring of cross of the F1 generation

INTRODUCTION TO GENETICS

Law of Dominance In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype. Parent Pea PlantsF1 Pea Plants Tall stem x short stemall tall stems yellow seeds x green seedsAll yellow seeds green pea pods x yellow pea podsall green pea pods round seeds x wrinkled seedsAll round seeds axial flowers x terminal flowersAll axial flowers

LAW OF SEGREGATION During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. Rr R r

LAW OF INDEPENDENT ASSORTMENT Alleles for different traits are distributed to sex cells (& offspring) independently of one another.

GENETIC TERMS Allele –Alternate forms of a gene –only 2 alleles normally –Represented by letters Dominant Allele – capital letter, expressed (A) Recessive Allele – lowercase letter, not expressed (a) Homozygous – same alleles (AA or aa) Heterozygous – mixed pair of alleles (Aa) Genotype – genetic composition Phenotype – physical appearance