The document discusses several of Gregor Mendel's discoveries and laws of genetics from his experiments with pea plants including: 1) Mendel's law of segregation which states that alleles for a gene separate into gametes during reproduction. 2) His law of independent assortment which states that different genes assort independently if located on separate chromosomes. 3) That dominant alleles are fully expressed in heterozygotes while recessive alleles have no visible effect.

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