Transcript Gregor Mendel Discovers The Principles of Inheritance

Gregor Mendel Discovers
The Principles of Inheritance
Lone Peak High School
Biology 2002-03
By Brad Shuler
Who was Gregor Mendel?
Born in 1822
Studied science,
mathematics and
statistics
Entered an Austrian
monastery to be a monk
Studied heredity in peas
Discovered the principles
of heredity
Mendel’s Observations
 He identified that pea plants have a variety of
traits when observing the different characteristics
of the plant.
 He developed “pure” strains of plants. (i.e. tall,
short, green pod, yellow pod, wrinkled, round,
etc.) These are often called purebreds.
 The purebred plants consistently produced
offspring with the given trait. (i.e. tall always
produced tall)
Mendel’s Peas
These are the seven characteristics, each having two
contrasting traits, that Mendel identified.
Mendel’s Experiments
 He experimentally
crosses different
strains of “pure”
plants (parental
generation) to develop
hybrids (F1
generation).
 He then crossed these
hybrids (F1 gen.) and
analyzed the results
(F2 gen.)
Mendel’s Results
 The hybrids (F1 gen.) only displayed one of the parental
traits. (tall)
 When crossing two hybrids, some of the resulting
offspring (F2 gen.) displayed one of the parental traits and
some displayed the other. (some tall some short)
 These traits in the F2 generation consistently occurred in a
3 to 1 ratio. (3 tall: 1short)
Mendel’s Conlusions:
The Principle of Segregation
 Each plant has two “factors” (genes) for any
given characteristic (length of stem, color of
pod, shape of seed, etc.)
 They receive these “factors” from their
parents.
 When a plant reproduces it only passes one of
its two “factors” to its offspring. The “factors”
are contained in the gametes, the egg or sperm.
Mendel’s Conlusions:
The Principle of Dominance and Recessiveness
 Factors for certain traits seem to mask or hide
the others when both are present in hybrids
(Tt=tall).
 Factors that are that always displayed when
present are called “dominant”.
 Factors that are hidden or masked by the
dominant are called “recessive”.
 Recessive traits are only displayed in
purebreds (i.e. short-tt, yellow pod-yy).
The End