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2. Concept : Mendelian Inheritance
• Learning Essential Question:
– Who is Mendel and what are his laws?
– Explain the relationship between traits
and heredity
– Explain the difference between
dominant and recessive traits.

3. Terms to know
Heredity/Inheritance: the passing of traits from one
generation to another
Traits: physical characteristics. Passed on through DNA
from parents to offspring through sexual reproduction,
Dominant Trait: a trait that is always expressed and
represented by a capital letter .Example: B for brown
hair
Recessive Trait: a trait that is only expressed if two
recessive alleles are present, represented by a lower
case letter. Example: b for blonde hair

4. Term to know!
Genotype- an organisms inherited combination of
alleles
Phenotype- an organisms inherited appearance
Genes- a segment of DNA that carries hereditary
instructions and is passed from parent to offspring
Alleles- multiple forms of the same gene
True-breeding- all of the offspring will have the same trait
as the parent when self-pollinate
First-generation- the very first set of offspring from two
parents

5. • Have you heard about clones, designer
babies and animals that grow human body
pats? These are developments of the science
of Genetics.
• Heredity is the passing of traits from one
generation to the next.
• The study of heredity is called genetics.
• Genes are located in the nucleus of each of
your cells
• Father of Modern Genetics. Austrian monk
born in 1822
• Mendel studied the inheritance of traits in pea
plants and develop the laws of inheritance.
Mendel used observation to study thousands
of pea plants over 7 years. He wanted to
understand how characteristics were passed
from one generation to the next.

6. The father of genetics
• While working in his
garden, Mendel
wondered why different
pea plants grew tall,
while others were short.
some had green seeds,
others yellow.
• He called all these
characteristics traits.
• Mendel was responsible
for figuring out that
each plant carried two
sets of instructions for
each characteristic
(one from the “mom”
and one from the
“dad”).

7. Gregor Mendel Discoveries
• Mendel discovered the principles of heredity and the
passing on of characteristics (traits) from parents to
offspring
After preforming
experiments with
pea plants. Mendel
found that the plants'
offspring retained
traits of the parents

8. In flowering plants, male reproductive cells called
pollen are created and stored on the anther. The
female reproductive cells are created and stored in the
ovary. When pollen touches the stigma, it falls through a
tube and into the ovary. Here, it combines with female
reproductive cells which begin to grow into seeds.
Stigma: Receives pollen
Ovary: Female
reproductive cells
Anther: Creates
pollen-male
reproductive cells
Seeds

9. Why Mendel choose pea plants?
I choose pea plants because they reproduce quickly, produces several
generations, can be artificially cross-pollinated and self-pollinate. Pea
plants are usually self-pollinating – meaning they can pollinate themselves,
even when they are alone. I was able to grow true breeding plants and
determine the traits for each generation
Cross-pollination
When the pollen from one
plant fertilizes the ovule of
a flower on a different
plant
Self-pollination
Has both female and
male structures, so
pollen from one flower
can fertilize the ovule
of the same flower

10. Some of the Traits studied in pea plants
Mendel investigated seven traits in pea plants. (stem length, pod shape,
seed shape, seed color, heigth,
Plant Height
Tall
Short
Flower color
Purple
petals
White
petals
Seed Color
Green
Yellow
Pod Shape
Smooth
Pinched
Pod color
Green Yellow
Seed Shape
Wrinkled
Round

11. How Mendel began his experiments
• Mendel developed a
method to crosspollinate plants by
moving the pollen
from one plant to the
pistil of another.
• Mendel handpollinated flowers
using a paintbrush
• He snipped the
stamens of each
flower to prevent selfpollination, then he
covered each flower
with a cloth bag and
finally he traced traits
through the several
generations
Pollen transferred
Parental
Generation
First Generation
offspring

12. Mendel crossed his pea plants
The first generation (F1)
of plants all had purple
flowers.
Where did the white
color go?
(pp)
Purple Parent (PP)
White Parent
• Mendel crossed
flowers that were
true-breeding for
each
characteristic.
• He crossed a
purple (PP)
flowered plant
with a white (pp)
flowered plant.
(Parent
Generation)
(Pp)
(Pp)
(Pp)
(Pp)

13. Mendel and His Peas
• In the second
generation (F2) he
had 3 purple
flowered plants,
and 1 white
flowered plant.
Purple Parent (Pp)
Purple Parent (Pp)
• Mendel took two
of his first
generation (F1 x
F1) purple
flowered plants
and crossed them
together.

14. • Mendel noticed in the
first generation, all of
the white flowers
seemed to disappear.
• He called this a
recessive trait.
• The white color faded
into the background
at first.
• It showed up in the
next generation when
he pollinated the
flowers. The color
(purple) that seemed
to mask over the
recessive color was
named the dominant
trait.

15. Dominant
Represented by a capital
letter
– this allele makes the trait
“show”, it can cover up or
mask other alleles
•Gene that always shows
Dominant trait-Strongest
trait
Black hair is dominant trait
Recessive
•Gene that only shows if
there is no dominant gene
present
•Represented by a lower
case letter
• this allele seems to
disappear when paired with
a dominant allele
Blonde hair is a recessive trait