1. Gregor Mendel
(1822-1884)
The Father of
Genetics
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade 1

2. Gregor Johann Mendel
Austrian monk
Studied the
inheritance of traits in
pea plants
Developed the laws of
inheritance
Mendel's work was
not recognized until
the turn of the 20th
century
2
© Fall 2005, Pflugerville ISD, 7th Grade

3. Gregor Johann Mendel
Between 1856 and
1863, Mendel
cultivated and tested
thousands of pea plants
He found that the
plants' offspring
retained traits of the
parents
copyright cmassengale 3
© Fall 2005, Pflugerville ISD, 7th Grade

4. Particulate Inheritance
Mendel stated that
physical traits are
inherited as “particles”
Mendel did not know
that the “particles” were
actually Chromosomes &
DNA
copyright cmassengale
© Fall 2005, Pflugerville ISD, 7th Grade 4

5. Why peas, Pisum sativum?
Can be grown in a
small area
Produce lots of
offspring
Produce pure plants
when allowed to self-
pollinate several
generations
Can be artificially
cross-pollinated
copyright cmassengale 5
© Fall 2005, Pflugerville ISD, 7th Grade

6. Mendel and His Peas
• Mendel tested 7 traits:
1. Flower color
2. Flower position
3. Seed color
4. Seed shape
5. Pod shape
6. Pod color
7. Plant height
http://www.fieldmuseum.org/exhibits/traveling_mendel.htm
© Fall 2005, Pflugerville ISD, 7th Grade

7. Mendel and His Peas
• 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)
http://biology.kenyon.edu/courses/biol114/KH_lecture_images/Mendel/Mendel.html
© Fall 2005, Pflugerville ISD, 7th Grade

8. Mendel and His Peas
Purple Parent (PP)
• The first
generation (F1) of
(pp)
plants all had
purple flowers.
(Pp) (Pp)
White Parent
• Where did the
white color go??
(Pp) (Pp)
© Fall 2005, Pflugerville ISD, 7th Grade

9. Mendel and His Peas
• Mendel took two of his
Purple Parent (Pp)
first generation (F1 x F1)
purple flowered plants
and crossed them
Purple Parent (Pp)
together.
• In the second (PP) (Pp)
generation (F2) he had
3 purple flowered
plants, and 1 white
flowered plant.
(Pp) (pp)
© Fall 2005, Pflugerville ISD, 7th Grade

10. Mendel and His Peas
• Mendel noticed in the first generation, all
of the white flowers seemed to
disappear.
• He called this a recessive allele.
• The white color faded into the
background at first.
• It showed up in the next generation
when he pollinated the flowers.
© Fall 2005, Pflugerville ISD, 7th Grade

11. Mendel and His Peas
• The color (purple) that seemed to mask
over the recessive color was named the
dominant allele.
© Fall 2005, Pflugerville ISD, 7th Grade

12. Mendel and His Peas
• 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”).
• Like many scientists, his work was not
accepted until after his death.
© Fall 2005, Pflugerville ISD, 7th Grade

13. Let’s Review
1. If you crossed a true-breeding black
rabbit with a true-breeding white
rabbit, all of the offspring would be
black. Which trait is dominant in
rabbits: black fur or white fur?
2. Which trait is recessive?
© Fall 2005, Pflugerville ISD, 7th Grade

14. Answer
Black Rabbit (BB)
• The trait for black
fur is dominant
over the trait for
White Rabbit (bb)
white fur. The
white fur trait is (Bb) (Bb)
recessive.
(Bb) (Bb)
http://www.buckeyevalleyfarms.freeservers.com/photo.html
© Fall 2005, Pflugerville ISD, 7th Grade

15. Google’s tribute to Mendel
July 2011
© Fall 2005, Pflugerville ISD, 7th Grade

16. Science Humor
© Fall 2005, Pflugerville ISD, 7th Grade

17. Mendel and His Peas
Vocabulary
1. Heredity- the passing of traits from
parent to offspring.
2. Trait- Each different form of a
characteristic such as stem height or
seed color.
© Fall 2005, Pflugerville ISD, 7th Grade

18. Mendel and His Peas
3. Genetics- The science of heredity.
4. Fertilization- A new organism begins to
form when egg and sperm join
together.
5. Purebred- An organism that is the
offspring of many generations that have
the same trait.
© Fall 2005, Pflugerville ISD, 7th Grade

19. Mendel and His Peas
7. Genes- a segment of DNA that carries
hereditary instructions and is passed
from parent to offspring; the factors
that control a trait.
8. Alleles- multiple forms of the same
gene.
9. Dominant Allele- one whose trait always
shows up in the organism when the
allele is present.
© Fall 2005, Pflugerville ISD, 7th Grade

20. Mendel and His Peas
10. Recessive Allele- A trait that is hidden
whenever the dominant allele is
present.
11. Hybrid- An organism that has two
different alleles for a trait.
© Fall 2005, Pflugerville ISD, 7th Grade