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Genetics Notes What is heredity? A. B. C. D. Traits passing from offspring to parents Traits passing from parents to offspring Plants that are cross-pollinated The ratio of dominant to recessive traits Heredity is “C” - The passing of traits from parent to offspring Who was Gregor Mendel? Austrian Monk Conducted his research in a monastery garden Worked with pea plants Discovered the principles of heredity Self-pollinating Peas Self-pollinating – when a plant fertilizes itself Results in a true-bred plant All the offspring of a true-bred plant will have the same trait as the parent Parent Offspring Cross-pollinating Peas When one plant fertilizes a different plant Pollen from one plant lands on the pistil and fertilizes the ovule (egg) of a different flower on a different plant • Wind • Bees & other insects First Generation Plants First Generation Plants Self -Pollinated X F2 Second Generation The white flowers reappeared! How did this happen? Alleles: *different forms of a gene *exist in pairs (one from mom & one from dad) Dominant allele– the prevailing (stronger) trait Capital Letter Recessive allele– the (weak) hidden trait Lower case letter Genotype – the combination of alleles you have for a specific trait • Ex: RR or Rr or rr Phenotype – the physical feature you show or see • Ex: Red flower petals, white flower petals Example: Gene: Flower Petal Color Alleles: • Red (R) • White (r) RR = homozygous dominant rr = homozygous recessive Rr = heterozygous Homo – the same Hetero - different Complete Dominance Rr = Red • dominant trait shows Co Dominance RW = Red & White • Both traits show Incomplete Dominance Rr = Pink • Traits are blended (mixed) First Generation Plants Self -Pollinated Rr RR Rr X Rr Rr rr The white flowers reappeared! HOW? The parents were heterozygous (Rr). F2 Second Generation Mendel’s Discoveries: Each trait has two sets of instructions (alleles), one from each parent Discovered dominant and recessive traits. Intro. to Punnett Squares A chart used to show all the ways genes from two parents can combine and be passed to offspring.
