Transcript Section 11-1: The Work of Gregor Mendel

Section 11-1:
The Work of Gregor Mendel
-The Father of Modern Genetics-
1. Genetics
• The scientific study of heredity
• Every living thing contains hereditary
information from its parent or parents
• Passed down through generations
Who is Gregor Mendel?
• A priest who worked in
a monastery and as a
high school teacher
• In charge of the
monastery garden
– Worked with garden
peas
– Laid the groundwork
for modern genetics
2. Mendel’s Peas: Reproduction
• The flower creates 2 types of pollen
– Male: Sperm
– Female: Egg cells
– Fertilization
• Joining of the male and female pollen
• Produces a tiny embryo encased in a seed
– Normally “Self Pollinating”
• They inherit all their genetic information from one
parent
Mendel’s Peas: Breeding
• 3. Each of his pea plants were “True-Breeding”
– If allowed to self pollinate they would produce
identical offspring
– Types of Pea Plants present:
– Height
• Tall Plants
• Short Plants
• Seed Color
– Green Peas
– Yellow Peas
Mendel’s Peas: The Cross Pollination
• Wanted to produce seeds by joining male and
female cells from two different plants
• 4. Cross Pollination
– Cut away pollen (male) from one plant and
dusting the female flower with the male pollen
– Made it possible to cross breed the plants and
observe the offspring
Cross Pollination Diagram
Genes and Dominance: Vocab
• 7. Traits
– Specific characteristic present in an organism
– EX: Hair Color
• 6. Hybrid
– Off spring of crosses between parents with different genetic traits
– EX: Humans
• 5. Genes
– Chemical factors that determine traits; passed down from parent
to offspring
– EX: Hair Color
• 8. Alleles
– Different forms of a gene
– EX: Red Hair, Brown Hair, etc.
Genetic Terms
• The P (Parental) generation
– The original pair of plants
• The F1 (first filial) generation
– The offspring of the P
generation
• The F2 (second filial)
generation
– The offspring of the F1
generation
Mendel’s Process
• Studied 7 pea plant traits
– Seed color or plant height variation
– Each trait had 2 contrasts
• EX: Height- Tall and Short
• Mendel crossed plants with each of the
contrasting traits and studied the offspring
– This had very interesting results
Results of P Cross
• When crossed all of the F1 generation plants
displayed only one of the 2 traits
– All plants were tall!
– The other trait seemed to disappear
• What happened?
Mendel’s Conclusions
• #1. Biological inheritance is determined by
factors passed from one generation to the
next
• 9. #2 .The Principle of Dominance
– Some alleles are dominant and others are
recessive
• Dominant: Trait will always be expressed
• 10. Recessive: Trait will be expressed only in absence of
dominant trait
Traits of Pea Plants
11. Dominant
• Height- Tall
• Seed Color- Yellow
• Seed Coat- Gray
• Pod Shape- Smooth
• Pod Color- Green
• Flower Position- Axial
• Seed Shape- Round
Recessive
• Height- Short
• Seed Color- Green
• Seed Coat- White
• Pod Shape- Constricted
• Pod Color- Yellow
• Flower Position- Terminal
• Seed Shape- Wrinkled
Mendel’s Process
• Mendel wanted to see if the recessive alleles
had disappeared or were still present
• 12. Allowed the F1 plant to self pollinate and
created an F2 generation with odd results.
– Resulted in 3 tall plants and 1 short plant
– The recessive allele had reappeared!
Results of the F1 Cross
• Resulted in 3 tall plants and 1 short plant
– The recessive allele had reappeared!
– 13. The recessive allele accounted for roughly ¼ of
the total plants…but how did this happen?
– Let’s look at the F1 cross in detail
F1 Cross-Explanation
• 14. The alleles for height segregated or
separated
– The alleles for tall and short separated during the
formation of the sex cells
• 15. These sex cells are called “Gametes”
– This allowed the recessive trait to cross pair with
another recessive and be present
16. F1 Cross Illustrated
Tt
17.Key
T- Dominant
t - Recessive
Tt
T
t
T
t
TT
Tt
Tt
tt
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