1. CHAPTER 9 Human GeneticsPp

2. heredity: transmission of characteristics from parent to offspring

3. Mendel Mendel’s Peas Observed 7 characteristics
Observed 2 traits within each characteristic
EX. CHARACTERISTIC: flower color
TRAIT: purple or white
Observations: purple flowering plants produced both purple and white flowering plants

4. Mendel’s Experiment (page 175)

5. Mendel’s Results
One trait was masked by a dominant factor and the trait that did not appear (in F1 but did in F2) was recessive
Trait controlled by a recessive factor is masked when paired with a dominant

6. Chromosomes and genes
Gene (located on a chromosome) codes for a characteristic (ie flower color)
Different forms of a gene = allele (i.e. purple or white)
Letters used to represent alleles
dominant trait capitalized (purple = P)
recessive lower case (white = p)

7. Genotypes and Phenotypes
Genotype: alleles an organism inherits
EX: PP Pp pp
Phenotypes: appearance due to the genotype
EX: PP (purple) Pp (purple) pp (white)
Homozygous: both alleles are alike (PP or pp)
Heterozygous: alleles are different

9. Rules
Law of segregation: paired factors separate during meiosis (formation of gametes)
Law of independent assortment: alleles sort independently of one another (not all dominant appeared together)