1. Genetics

5. MONOHYBRID CROSS inheritance of a single trait P Generation (true-breeding parents) Purple flowers White flowers x F 1 Generation (hybrids) All plants had purple flowers F 2 Generation 705 plants 224 plants self-pollination

8. P Generation F 1 Generation F 2 Generation P p P p P p P p Pp PP pp Pp Appearance: Genetic makeup: Purple flowers PP White flowers pp Purple flowers Pp Appearance: Genetic makeup: Gametes: Gametes: F 1 sperm F 1 eggs 1 / 2 1 / 2 x True-breeding plants have identical alleles. Gametes each contain only one allele for the flower-color gene. Every gamete produced by one parent has the same allele. F 1 hybrids have a Pp combination. Purple-flower allele is dominant, all hybrids have purple flowers. Hybrid plants produce gametes, two alleles segregate: half the gametes receiving the P allele and the other half the p allele. 3 : 1 Punnett square: shows all possible combinations of alleles in offspring from an F 1 x F 1 ( Pp x Pp ) cross. Each square represents an equally probable product of fertilization. Random combination of the gametes results in the 3:1 ratio that Mendel observed in the F 2 generation.

10. The test-cross X Dominant phenotype, unknown genotype: PP or Pp ? Recessive phenotype, known genotype: pp If PP , then all offspring purple: If Pp , then 1 ⁄ 2 offspring purple and 1 ⁄ 2 offspring white: p p P P Pp Pp Pp Pp pp pp Pp Pp P p p p APPLICATION An organism displaying the dominant phenotype can either be homozygous or heterozygous for the trait. A test-cross will help determine which. TECHNIQUE The individual with the unknown genotype is crossed with a homozygous individual expressing the recessive trait (white flowers in this example). By observing the phenotypes of the offspring resulting from this cross, we can deduce the genotype of the purple-flowered parent. RESULTS

12. Law of independent assortment - allele pairs separate independently during the formation of gametes

13. Forked Line Method AaBbCc x AaBbCc