Gregor Mendel was an Austrian monk who studied inheritance of traits in pea plants between 1856-1863. He cultivated and tested thousands of pea plants, finding that their offspring retained traits of the parents. Mendel's work established the laws of inheritance and showed that traits are inherited as discrete particles, now known as genes. However, his work was not widely recognized until the early 20th century.

1. Gregor Mendel
(1822-1884)
The Father of
Genetics
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© 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
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© 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
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© 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
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© 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 trait.
• 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 trait.
© 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
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15. Google’s tribute to Mendel
July 2011
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16. Science Humor
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17. Mendel and His Peas
Vocabulary
1. Heredity- the passing of traits from
parent to offspring.
2. Self-pollinate- A plant is often able to
pollinate by itself because it contains
both the male and female reproductive
structures. This only requires 1 parent.
© Fall 2005, Pflugerville ISD, 7th Grade

18. Mendel and His Peas
3. True-breeding- all of the offspring will
have the same trait as the parent when
self-pollinated
4. First-generation- the very first set of
offspring from two parents
5. Dominant trait- the trait observed when
at least one dominant allele for a
characteristic is inherited
© Fall 2005, Pflugerville ISD, 7th Grade

19. Mendel and His Peas
6. Recessive trait- a trait that is apparent
only when two recessive alleles for the
same characteristic are inherited
7. Genes- a segment of DNA that carries
hereditary instructions and is passed
from parent to offspring
8. Alleles- multiple forms of the same
gene
© Fall 2005, Pflugerville ISD, 7th Grade

20. Mendel and His Peas
9. Genotype- an organisms inherited
combination of alleles
10. Phenotype- an organisms inherited
appearance
© Fall 2005, Pflugerville ISD, 7th Grade