Introduction to Genetics Ch 9

The Work of Gregor Mendel A. The branch of biology that studies heredity is called genetics. B. Gregor Mendel is considered the father of genetics who studied in a monastery. C. He planted hundreds of pea plants to study their traits. D. He self-pollinated plants: 1. He brushed the pollen of one plant onto itself

2. These parents inherited all the characteristics of the single plant that bore them. E. He also cross pollinated plants. 1. He brushed the pollen of one plant onto another.

2. He discovered that purebred tall plants would only produce tall offspring. F. He studied many traits. 1. Other characteristics of the pea plants are:

Round peas or Wrinkled Yellow peas or Green Gray peas or White Smooth pods or Constricted Green pods or Yellow Axial or Terminal Tall or Short

I. Dominance vs. recessive traits: 1. Dominant traits show through with one parent’s dominant trait: Ex. Tt = Tall 2. This is known as a hybrid or heterozygous (two different traits) T= Dominant for tallness t= Recessive for shortness 3. An organism will always show the dominant trait.

4. Recessive traits show through only when an organism has two recessive traits. 5. Ex. tt = short 6. TT or tt are considered purebred or homozygous because both genes from the mother and the father are the same.

7. Phenotype: The physical appearance of the offspring in a punnett square. 8. Genotype: The genetic makeup of the offspring.

J. Mendel’s experiment: F1 generation (segregation) He crossed a purebred for tallness with a purebred for shortness: TT x tt

The F2 generation would be Tt xTt

Do the following cross: Cross a hybrid for tallness with a purebred for shortness: Tt x tt

Do the following cross: Two parents are hybrid for brown hair. What are the probabilities of their offspring having brown or blond hair?