The Monk who loved peasThe Monk who loved peas

How to Make a Living Thing

Gregor MendelGregor 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 2nd generation

So Mendel began to experiment, attempting to grow peas with certain traits, or characteristics

The Proof is in the PeasThe 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 parentOr, they can cross-pollinate with other peas

The ExperimentThe 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 DiscoveryMendel’s Discovery Mendel noticed the

offspring of a purple-flowered pea plant and a white one was always purple

BUT, the “grandchildren” or 2nd generation, would have 1 white-flowered pea plant for every three purple ones

Dominant TraitsDominant 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 TraitsRecessive Traits “Fade into the back”

The white-flowered pea plant

These traits reappear in the 2nd generation

MUST be paired with another recessive allele

R r

R RR Rr

r Rr rr

Incomplete DominanceIncomplete 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

GenesGenes 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.

AllelesAlleles 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 PhenotypeGenotype 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 PedigreesGenetic 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