1. Section 6-3 “Mendel”

2. Gregor Mendel (born in 1822) was an Austrian monk who discovered the basic principles of heredity through experiments in his garden.
Mendel conducted hybridization experiments on around 29,000 pea plants
Mendel's observations became the foundation of modern genetics and the study of heredity, and he is widely considered the “father of genetics.”

3. Mendel chose to use peas for his experiments because:
pea plants have many distinct varieties
offspring could be quickly and easily produced.
control how the plants mated
He cross-fertilized (hybridized) pea plants that had clearly opposite characteristics—tall with short, smooth peas with wrinkled peas, plants containing green seeds with those containing yellow seeds, etc.
After analyzing his results, Gregor Mendel reached two of his most important conclusions:

4. Law of Segregation: Two genes coding for the same trait separate during gamete formation. Organisms inherit two copies of each gene, one from each parent.
Gene
Chromosome

5. Law of Independent Assortment: Genes for one type of trait separate independently from genes of another type of trait
In other words…A gene for one trait is not inherited together with another gene for a different trait.

7. If you cross a white flower with a purple flower what will you get?x =

8. A red and white would make pink Mendel proved this was not true
Many people in Mendel’s day thought traits were blended …. A purple flower and a white flower would make a lavender flower
A red and white would make pink
Mendel proved this was not true
Mendel Laws of Inheritance
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9. KEY CONCEPT Traits (characteristics) are inherited as discrete (separate) units

10. Traits are distinguishing characteristics that are inherited (like hair color or blood type)
Genetics is the study of biological inheritance patterns and variation
Heredity: The passing of traits from parents to offspring

11. The uniting of male and female gametes (sex cells) Plants “pollinate”
Fertilization
The uniting of male and female gametes (sex cells)
Plants “pollinate”
A hybrid plant would have one of each form of a trait

12. Mendel controlled the
fertilization of his pea plants
by removing the male parts,
or stamens.
He then fertilized the female
part, or pistil, with pollen from
a different pea plant.

13. Mendel’s 1st Experiments
Mendel’s 1st experiments were called monohybrid crosses (the plants were different by just one trait)
Example: all pea plants had purple flowers and green seeds, but some are tall and some short

14. Mendel’s 1st Generation
He crossed a pea plant that was pure for purple flowers (it had only purple genes) with a plant that was pure for white flowers (only white genes).
The offspring were all purple, no white pea flowers grew
The white trait seemed to disappear

15. P1 = parent in the 1st generation
The offspring of P1 were called the F1 generation
“F” stands for filial
Filial stands for son or daughter

16. Mendel’s 2nd Generation
Mendel crossed two of the offspring from the 1st generation
His results were 3 of every 4 plants were purple and 1 in 4 was white
The white trait reappeared

17. P1 = parent in the 1st generation
The offspring of P1 were called the F1 generation
“F” stands for filial Filial stands for son or daughter
The offspring of the cross between 2 F1 plants were called the F2 generation

18. What disappeared in the 1st generation?
The trait for white
What reappeared in the 2nd generation?

19. Mendel observed patterns in the first and second generations of his crosses

20. Mendel’s Conclusions
Mendel concluded that each organism has 2 factors that control each of its traits
The factors controlling traits are called genes
One comes from each parent
They are found on the chromosomes
Genes exist in alternative forms

21. Law of Segregation:
During fertilization, the 2 different genes randomly pair to produce 4 different combinations of alleles
They separate independently

22. Draw the next slide

23. Law of Segregation
Parents Tt Tt x
T T Tt Tt tt
Offspring

24. T T tt Tt Parents x Offspring Law of Segregation
• Organisms inherit two copies of each unit (gene), one from each parent.
• The two copies separate, or segregate, during gamete formation. As a result, organisms donate only one copy of each unit (gene) in their gametes.
Parents x
Offspring Tt
T T tt

25. Law of Segregation:
During the production of gametes the two copies of each gene segregate so that offspring acquire one gene from each parent.

26. Mendel’s Genetics
Gregor Mendel
Mutant Animal Pets