1. Introduction to Genetics
Chapter # 11
Introduction to Genetics

2. Who is Gregor Mendel?

3. I. The Work of Gregor Mendel
Genetics – study of heredity.
A. Gregor Mendel’s Peas
Gregor Mendel – Austrian monk
who experimented with garden pea
plants to learn more about
inheritance. Is known as the “Father
of Genetics”.
-Mendel worked with 2 basic types
of pea plants : tall & short. The
seeds of one were yellow & the
seeds of the other were green.

4. Self vs. Cross Pollination
-Mendel’s pea plants reproduced by means of self
pollination – process by which a flower on a plant
is pollinated by pollen from that same plant.
-Self-pollinating plants are sometimes called
true-breeding – when permitted to self pollinate,
they produce offspring identical to themselves.
-Mendel did experiments in which he cross
pollinated his pea plants.
Cross-pollination – the pollination of a flower by
pollen from a completely different plant (involves 2
parents).

5. B. Genes and Dominance -Mendel studied 7 different
traits in pea plants.
Trait – a specific characteristic,
ex : seed color.
-Each trait studied had a
contrasting trait, ex : green vs.
yellow seed color.
-Mendel crossed plants with
the 7 contrasting traits &
studied their offspring.

6. P1, F1, & F2 -We call the original pair of plants
the P (parental) generation & their
offspring the F1 or first filial
generation. Filius/filia = Latin for
son/daughter.
-The offspring of F1 are referred
to as the second filial generation (F2).
*Offspring of crosses between
parents with different traits are
called hybrids.

7. Mendel’s Conclusions Mendel concluded that :
1. Biological inheritance is determined by factors that are passed from one generation to the next.
-The chemical factors that determine traits are genes.
-Each trait is controlled by one gene that occurs in 2
contrasting forms. The contrasting forms produce different
characters of each trait.
-Different forms of a gene are alleles.
2. The Principal of Dominance, which states that some alleles are dominant & others are recessive.
-Dominant alleles are expressed if in an allele pair. Recessive
alleles are expressed if no dominant alleles are present in an
allele pair (D = tall/yell).

8. C. Segregation -Mendel crossed F1 plants with each other to find out
what happened to the
recessive traits.
-Mendel’s F1 cross resulted
in a re-appearance of the
recessive traits in the F2
plants (about 1 of 4 were
short).
This is due to segregation –
separation of alleles during
gamete formation.

9. Gamete Formation *When gametes are produced, the two alleles
segregate from each other so
that each gamete carries only
a single copy of each gene.
So, each F1 plant produces 2
kinds of gametes : ones with
alleles for tallness & ones
with alleles for shortness.
Dominant alleles are
represented with capital
letters & recessive alleles
with lower case letters, ex :
T=tall, t=short.