1. Learning Goal 1
The Work of Gregor Mendel
Background on Gregor Mendel
Details -
Reasons for Choosing Peas -
Mendel’s Experimental Design
His Pea Experiment -
Mendel’s Results -
Mendel’s Laws
Law of Dominance -
Law of Segregation -
Law of Independent Assortment -
Genetic Terms
Alleles -
Homozygous -
Heterozygous -
Genotype -
Phenotype -

2. Unit IV
Learning Goal 1
Describe the research of Gregor
Mendel and predict the outcome of
genetic crosses.

3. Background on Gregor Mendel
• Details
• Austrian monk with an
interest in gardening
and a good
knowledge of
mathematics.
• In the 1840’s he
experimented with the
traits of garden peas
(Pisum sativum).

4. Reasons for Choosing the
Garden Pea
• Many varieties exist.
• Easy to observe
contrasting traits.
• They self-pollinate.
• They reproduce
quickly.

5. Mendel’s Experimental
Design
• His Pea Experiment
• He allowed each variety to
self-pollinate for several
generations to ensure that they
were true-breeding (offspring
always exhibited the same
trait). He called this the P1
(parent)Generation.
• He took two of these parent
plants with contrasting forms of
the same trait and cross-
pollinated them.
• The plants that resulted from
this cross were called the F1
Generation.
• Mendel then allowed the F1
plants to self-pollinate to
produce the F2 Generation.

6. Mendel’s Results
• For every trait, one form would
disappear from the F1
generation.
• The disappearing trait
reappeared in the ¼ of the F2
generation.
• This was true of all seven traits
that Mendel looked at.
• He used the term dominant to
refer to the form of the trait
exhibited in the F1 generation
and recessive to refer to the
disappearing trait.

7. Mendel’s Laws
• Law of Dominance –
One form of each trait is dominant and one is
recessive.

8. Law of Segregation
• Members of each
gene pair (alleles)
separate during
gamete formation (
meiosis).

9. Law of Independent Assortment
• The genes for
different traits
separate
independently from
one another during
gamete formation.

10. Genetic Terms
• Alleles – members of a gene pair symbolized by
letters. Dominant alleles are capital letters, and
recessive alleles are lower case.
• Homozygous – the alleles of a gene pair are
identical (RR or rr).
• Heterozygous – the alleles of a gene pair are
different (Rr).
• Genotype – describes the types of alleles of a
gene pair
• Phenotype – describes the expression of the
trait in the appearance.