Genetics: the study of heredity - how traits get passed from one generation to the next
ex: eye color, blood type, skin color
Gregor Mendel - An Austrian monk (mid 1800's) who was a gardener. Pioneer in studying genetic inheritance which is a huge component in biology.
Mendel's Experiments
Key terms:
self-pollination: pollen (sperm) from a plant fertilize its own eggs. The resulting seeds are all identical to themselves.
same plant!
cross-pollination: pollen from one plant fertilizes the eggs of another plant
two plants
Mendel's Experiments
Mendel called:
P = original parent generation (your parents)
F1 = 1st generation offspring (you)
F1 offispring of parents with different traits are called hybrids
F2 = 2nd generation offpring (your kids)
When Mendel crossed plants, the F1 looked like only 1 parent, not a blend of the two traits!
Mendel's Conclusions:
Inheritance and Dominance
Inheritances is determined by "factors" called genes, which are small portions of DNA that code for proteins
The proteins then control how a trait is expressed
Each trait Mendel studied was controlled by two genes that come in contrasting forms
Ex: the gene for "plant height" comes in two forms - tall & short
the two forms of a gene are called alleles
Mendel's Conclusions:
Inheritance and Dominance
Principle of Dominance
Some alleles are dominant and some are recessive
An organism that has a dominant allele for a trait will always express the dominant form
An organism that has a recessive allele for a trait will only show the recessive form of the trait when the dominant allele is not present
A dominant allele can mask or hide a recessive allele - Mendel noticed that the recessive form seemed to disappear in the F1 generation and reappear in the F2 generation
Mendel's Conclusions:
Law of Segregation
The pair of genes for a trait separate from one another in meiosis.
When Mendel crossed his F1 plants, the recessive form of the trait showed up in the F2
Ex: a parent plant who is Tt can pass an T or t to the offspring via the egg
The result of this process is an F2 generation with new combinations of alleles