Inheritance of
Traits: The
Work of
Gregor
Mendel
1. What does the science of genetics study?
2. Why is Gregor Mendel called the Father of
Genetics?
3. Why did Mendel chose pea plants for his
experiments?
a.
b.
c.
1. What does the science of genetics study?
heredity: the passing of traits from one
organism to its offspring
2. Why is Gregor Mendel called the Father of
Genetics?
3. Why did Mendel chose pea plants for his
experiments?
a.
b.
c.
Gregor Mendel
• Born in 1822 in Austria.
• He became a Monk and then studied math and science.
• He was also in charge of the monastery garden, where he studied
pea plants and their flowers.
 Pea flowers are made of Male and Female parts
(M -pollen, F -eggs which get fertilized into seeds)
 Pea plants self-pollinate pollen fertilize the egg cells in
the same plant.
 So, If a pea plant self-pollinates, what characteristics will the
seed (and plant) inherit?
1. What does the science of genetics study?
heredity: the passing of traits from one
organism to its offspring
2. Why is Gregor Mendel called the Father of
Genetics? His experiments with pea plants were
the first to study heredity/ genetics
3. Why did Mendel chose pea plants for his
experiments?
a.
b.
c.
1. What does the science of genetics study?
heredity: the passing of traits from one
organism to its offspring
2. Why is Gregor Mendel called the Father of
Genetics? His experiments with pea plants were
the first to study heredity/ genetics
3. Why did Mendel chose pea plants for his
experiments?
a. grow and reproduce quickly
b.
c.
1. What does the science of genetics study?
heredity: the passing of traits from one
organism to its offspring
2. Why is Gregor Mendel called the Father of
Genetics? His experiments with pea plants were
the first to study heredity/ genetics
3. Why did Mendel chose pea plants for his
experiments?
a. grow and reproduce quickly
b. have many different traits that can be studied
at the same time
c.
Pea Plant Traits
Seed
Shape
Seed
Color
Round
Yellow
Wrinkled
Green
2 different
characteristics
for Round
each trait Yellow
Seed Coat
Color
Pod
Shape
Pod
Color
Flower
Position
Gray
Smooth
Green
Axial
Tall
White
Constricted
Yellow
Terminal
Short
Gray
Smooth
Green
Axial
Plant
Height
Tall
1. What does the science of genetics study?
heredity: the passing of traits from one
organism to its offspring
2. Why is Gregor Mendel called the Father of
Genetics? His experiments with pea plants were the
first to study heredity/ genetics
3. Why did Mendel chose pea plants for his
experiments?
a. grow and reproduce quickly
b. have many different traits that can be studied
at the same time
c. easy to breed through cross-pollination
4. What is pollination?
What is self-pollination?
What is cross-pollination?
4. What is pollination? Transfer of pollen from
the male part of a flower to the female part of a
flower
What is self-pollination?
What is cross-pollination?
4. What is pollination? Transfer of pollen from
the male part of a flower to the female part of a
flower
What is self-pollination? One plant pollinates
itself
What is cross-pollination?
4. What is pollination? Transfer of pollen from
the male part of a flower to the female part of a
flower
What is self-pollination? One plant pollinates
itself
What is cross-pollination? Transfer pollen from
one plant to another
5. In the box below, label the drawing of a
flower, including the stigma, style, ovary,
anthers, filaments, pollen, petals, and sepals.
petals
Male part:
Stamen
Female part:
Pistil
Stigma
Anther
Pollen
(sperm)
Filament
sepals
Style
Ovary (eggs)
6. What is meant by the term true-breeding? Use pea
plants as an example.
7. Mendel found that short pea plants were always
true-breeding. Tall pea plants however are not always
true-breeding. Sometimes crossing two tall plants
produces offspring that are short. If you had several
tall pea plants, how could you determine whether or
not they were true-breeding?
6. What is meant by the term true-breeding? Use pea
plants as an example. A plant that always produces
offspring that look like itself (i.e. a tall plant that always
produces tall offspring)
7. Mendel found that short pea plants were always
true-breeding. Tall pea plants however are not always
true-breeding. Sometimes crossing two tall plants
produces offspring that are short. If you had several
tall pea plants, how could you determine whether or
not they were true-breeding?
6. What is meant by the term true-breeding? Use pea
plants as an example. A plant that always produces
offspring that look like itself (i.e. a tall plant that always
produces tall offspring)
7. Mendel found that short pea plants were always
true-breeding. Tall pea plants however are not always
true-breeding. Sometimes crossing two tall plants
produces offspring that are short. If you had several
tall pea plants, how could you determine whether or
not they were true-breeding? Allow tall plants to selfpollinate. If they produce only tall offspring, they are
true-breeding. If they produce some short offspring,
they are NOT true-breeding.
8. Mendel’s Experiment
Plant Height
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
TT
tt
Tt
Tt
TT
Tt
Tt
tt
9. What is the P1 generation?
What is the F1 generation?
F2?
9. What is the P1 generation? Parental
generation
What is the F1 generation?
F2?
9. What is the P1 generation? Parental
generation
What is the F1 generation? First generation of
offspring
F2?
9. What is the P1 generation? Parental
generation
What is the F1 generation? First generation of
offspring
F2? Second generation of offspring
9. What is the P1 generation? Parental generation
What is the F1 generation? First generation of offspring
F2? Second generation of offspring
10. What happened to the shortness trait during
the F1 generation of Mendel’s experiment?
How did Mendel explain this occurrence?
9. What is the P1 generation? Parental generation
What is the F1 generation? First generation of offspring
F2? Second generation of offspring
10. What happened to the shortness trait during
the F1 generation of Mendel’s experiment? It
was hidden – all plants in F1 were Tt so they
appeared tall even though they had a “t” (short)
How did Mendel explain this occurrence?
9. What is the P1 generation? Parental generation
What is the F1 generation? First generation of offspring
F2? Second generation of offspring
10. What happened to the shortness trait during
the F1 generation of Mendel’s experiment? It
was hidden – all plants in F1 were Tt so they
appeared tall even though they had a “t” (short)
How did Mendel explain this occurrence? Must
be two factors controlling each trait; 2 tall
factors = tall, 2 short factors = short; 1 tall + 1
short factor = tall
Terminology
Gene: sequence of DNA that codes for a trait
Alleles: different forms of a gene
Principle of dominance: dominant trait is
always seen when dominant allele is present;
recessive trait is only seen when no dominant
allele is present
Recessive allele: allele that is masked in
phenotype when dominant allele is present
–
Allele for blue eyes
Dominant allele: allele that is always expressed in
phenotype when it is present
– Allele for brown eyes
Notation
When diagramming genetics experiments or
solving genetics problems:
• A single letter of the alphabet is chosen to
represent each trait (example: T)
 A capital letter represents the dominant allele (T).
 A lower case letter represents the recessive allele (t).
Example: Pea plant height – T=tall, t=short
Pea Plant Traits
Seed Coat
Color
Pod
Shape
Seed
Shape
Seed
Color
Round
Yellow
Gray
Wrinkled
Green
White
Constricted
Round
Yellow
Gray
Smooth
Smooth
Pod
Color
Green
Flower
Position
Plant
Height
Axial
Tall
Yellow
Terminal
Short
Green
Axial
Tall
12. What is a hybrid?
Can a short pea plant ever be a hybrid?
Explain.
• Hybrid: Organism with two different factors
(alleles) for a trait (ex. T t)
Example: Cross pollinate a true breeding red
flower and a true breeding white flower.
Seedlings=hybrid
X
=
Hybrid Cars
Gas + Electric
8. Mendel’s Experiment
Plant Height
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
TT
tt
Tt
Tt
TT
Tt
Tt
tt
12. What is a hybrid? Organism with two
different factors (alleles) for a trait (ex. T t)
Can a short pea plant ever be a hybrid?
Explain.
8. Mendel’s Experiment
Plant Height
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
TT
tt
Tt
Tt
TT
Tt
Tt
tt
12. What is a hybrid? Organism with two
different factors (alleles) for a trait (ex. T t)
Can a short pea plant ever be a hybrid? No
Explain. Short factor is recessive – whenever
tall factor is present, it will hide the short
13. Use a labeled, colored drawing to show what would happen
if you crossed a true-breeding round-seed plant with a truebreeding wrinkled seed plant, and then crossed two of the F1
plants. Be sure to show the P, F1, and F2 generations.
13. Use a labeled, colored drawing to show what would happen
if you crossed a true-breeding round-seed plant with a truebreeding wrinkled seed plant, and then crossed two of the F1
plants. Be sure to show the P, F1, and F2 generations.
P
X
RR
rr
F1
X
Rr
Rr
F2
RR
Rr
Rr
rr
Mendel did his work before DNA!
Pea Plant DNA
(Electron
Microscope)