The Monk who loved peas How to Make a Living Thing

Gregor Mendel  Monk, failed teacher, pea-lover, genetic genius  From growing peas, Mendel noticed that offspring did not always have the same traits as the parents But then the parent’s trait would show up again in a “grandchild,” or 2 nd generation  So Mendel began to experiment, attempting to grow peas with certain traits, or characteristics

The Proof is in the Peas  Peas were an excellent choice for his research for two reasons They can self-pollinate, creating offspring with the same traits as the parent Or, they can cross- pollinate with other peas

The Experiment  Mendel looked at one characteristic at a time (color, height, shape)  If a pea plant has a white flower, then it self- pollinates, you’ll have offspring with white flowers  What happens if a purple-flowered pea plant cross-pollinates a white-flowered pea plant?

Mendel’s Discovery  Mendel noticed the offspring of a purple- flowered pea plant and a white one was always purple BUT, the “grandchildren” or 2 nd generation, would have 1 white-flowered pea plant for every three purple ones

Dominant Traits  Dominant traits are the ones always showing up in the first generation The purple-flowered pea plant  In a Punnett Square, dominant traits are symbolized by a capital letter

Recessive Traits  “Fade into the back” The white-flowered pea plant  These traits reappear in the 2 nd generation  MUST be paired with another recessive allele Rr R RRRrRr r RrRr rr

Incomplete Dominance  Sometimes, one trait is NOT dominant over the other  Each allele provides some influence  Hair texture—curly, straight, and wavy—is an example in humans

Genes  The instructions for one particular trait are called a gene  You have 2 forms of the same gene for every characteristic 1 from Mom, 1 from Dad  Hair color, eye color, height, hitchhiker’s thumb, etc.

Alleles  The form of a trait given by one parent  So, for each gene, you have 2 alleles  Either dominant (capital letter) or recessive (lower-case)

Genotype and Phenotype ·Both inherited traits form a genotype --Aa; rr; etc. ·The appearance of a characteristic is the organism’s phenotype --a purple flower; wrinkled peas; wavy hair

Genetic Probability and Pedigrees  Probability is the mathematical chance of an outcome  Aa x Aa has a 25% chance of getting aa as an outcome; 25% AA; 50% Aa  Pedigrees are like family trees for determining the probability of genetic diseases like cystic fibrosis