The History
Of
Genetics:
Gregor
Mendel
and his
Peas
• Genetic first started when an Austrian
monk, named Gregor Mendel,
performed a series of experiments on
garden peas.
• Mendel observed qualitative
information about the traits of the pea
plants. He then tried to quantify how
those traits were passed from one
generation to another.
• Mendel developed purebred lines of
pea plants. He recorded the results of
his experiments and made statistical
notes about how the traits were passed
down.
The results of Mendel’s studies were so important that he is considered:
Father of Genetics
WHY PEAS?
•
•
•
•
•
Structure of the pea flowers
Presence of distinctive traits
Rapid reproduction cycle
Grow quickly
Produce large number of
offspring
• Cheap and easy to grow and
maintain
• Pea plants normally selfpollinate but can crosspollinate if the anthers (the
boy parts) are removed
when the flower is young
stigma
Anther-holds
male gametes
filament
style
petal
Ovary (holds
female
gametes-eggs)
sepal
Self Pollination
• Self-pollination
female and male
gametes (egg &
pollen) from the
same plant form a
zygote
example: this is how
plants normally go
about their
business
Petals form a tent over the stigma and anthers
Pollen is trapped inside
Purple Flower
pollen
*
Pollen (gamete from the
boy part) goes to the stigma
( the girl part) of the same
flower fertilizes the female
gamete
Cross-pollination
• Cross-pollination
female and male
gametes from two
different plants form
a zygote
example: Mendel
“painted” pollen from
one plant onto the
stigma of another
plant, or insects
transfer pollen from
one plant to another
Mendel cut off
the anthers so
the plant does
not produce its
own pollen.
Mendel painted
pollen from another
plant onto the stigma
of the flower
Mendel studied characteristics in the parents and offspring of
pea plants. The plants displayed several easily-observed
characters in one of two contrasting traits or forms
Mendel studied characteristics in the parents and offspring of
pea plants. The plants displayed several easily-observed
characters in one of two contrasting traits or forms
Trait or Characteristic
(coded for by a gene)
Alleles or Forms of the Trait
Seed color
yellow and green
ATGCCAGCTACC
yellow
Different sequences
Seed shape
wrinkled and smooth
Flower color
purple and white
Pod color
yellow and green
CTGACCGTACCG
green
Mendel observed that there were two
different types of pea plants
Purebred
Plants
• plants that, when self-pollinated,
produce the same form of a trait
in all offspring
• Example: white flower plants that
produce offspring with white
flowers
Hybrid
Plants
• plants that, when self pollinated,
produce more than one form of a
trait in their offspring
• Example: Purple flower plants
that produce some purple and
some white flowered offspring
• Mendel performed his experiments with
great patience and precision. He kept careful
records. Mendel’s work spanned 10 years and
involved over 280 genetic crosses producing
some 28,000 pea plants.
• Mendel was trained in mathematics and used
his background in probability to analyze the
results of his crosses.
Describe (briefly) the experiments
that Gregor Mendel set up.
• Mendel set up crosses with pea plants to see
how their traits were passed down from
generation to generation
Why were pea plants an ideal choice
for Mendel’s experiments? (give at
least three reasons)
•
•
•
•
•
•
•
Structure of the pea flowers
Presence of distinctive traits
Rapid reproduction cycle
Grow quickly
Produce large number of offspring
Cheap and easy to grow and maintain
Pea plants normally self-pollinate but can crosspollinate too
What were some the traits he
observed? What were the different
alleles for these traits?
Traits
Dominant Allele
Recessive Allele
Flower color
Purple
White
Seed Color
Yellow
Green
Pod Color
Green
Yellow
Pod Shape
Full
Constricted
Seed Shape
Round
Wrinkled
Flower Position
Axial
Terminal
Plant Height
Tall
Short