1. The Fundamentals of Genetics
Section 1: Mendel’s Legacy

2. Definition
Genetics is the study of how characteristics are passed down from parents to offspring

3. The Language of Genetics
Heredity is the transmission of characteristics from parents to offspring
A characteristic is an inheritable feature, such as flower color.
A trait is a genetically determined expression of a characteristic such as a red flower

4. History of Genetics
It all started with a monk named Gregor Mendel & some pea plants

5. Gregor Mendel “Father of Genetics”
Was an Austrian monk and a high school teacher
Researched & published the heredity of pea plants in 1865
Discovered 7 characteristics in pea plants
From his research, he established 3 basic laws of inheritance

6. Mendel’s Methods
Mendel was able to observe heredity of pea plants by controlling their pollination
Pollination occurs when pollen grains in the male parts of a flower are transferred to the female part of a flower
Self-pollination occurs when pollen is transferred from the anthers of a flower to the stigma of either that flower or another flower on the same plant
Cross-pollination occurs between flowers of two plants

7. Mendel’s Methods

8. Mendel’s Experiments
Began with true-breeding plants for each of the traits he wanted to study using cross-pollination
He then cross-pollinated pairs of plants that were true-breeding for contrasting traits of single characteristic such tall vs. short plants

9. Mendel’s Results True-breeding plants = P generation or parents
Interest Grabber
Mendel’s Results
Parents
1st Generation
2nd Generation
Long stems x short stems
All long
787 long; 277 short
Red flowers x white flowers
All red
705 red; 224 white
Green pods x yellow pods
All green
428 green; 152 yellow
Round seeds x wrinkled seeds
All round
5474 round; 1850 wrinkled
Yellow seeds x green seeds
All yellow
6022 yellow; 2001 green
True-breeding plants = P generation or parents
The offspring of the P generation is called the first filial generation or the F1
The offspring of the F1 generation is called the second filial generation or the F2
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10. Mendel’s Experiments

11. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
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12. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
Tall
Tall
Tall
Tall
Tall
Short
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13. Principles of Dominance
Section 11-1
P Generation
F1 Generation
F2 Generation
Tall
Short
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14. Questions
In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
How do the characteristics of the second generation compare to the characteristics of the first generation?

15. Mendel’s Conclusions
Mendel concluded that something within the pea plants controlled the characteristics he observed
He called these controls factors
He then hypothesized that each trait was inherited by means of a pair of factors
He reasoned further that because the characteristics studied had 2 alternative forms, a pair of factors must control each trait

16. Dominant & Recessive Traits
Dominant Factors are those that dominate the factor for the other trait in the pair
Recessive Factors are those that are masked by dominant factors and only appear when both factors of the trait are both recessive
Factors are better known as alleles

17. Writing Alleles We use letters to represent the alleles of a trait
Capital letters are dominant alleles
Lowercase letters are recessive alleles
For example:
R = red flower r = white flower
Alleles always come in pairs

18. Which is the dominant trait?
Section 11-1
Seed Shape
Flower Position
Seed Coat
Color
Seed Color
Pod Color
Plant Height
Pod
Shape
Round
Wrinkled
Yellow
Green
Gray
White
Smooth
Constricted
Axial
Terminal
Tall
Short
What might happen in the F2 generation? Why?
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19. Mendel’s Three Laws
Law of Dominance: states that some alleles are dominant while others are recessive
Law of Segregation: states that alleles are separated during gamete formation
Law of Independent Assortment: states that alleles are independently sorted during gamete formation

20. Gregor Mendel
Experimented
with
He concluded
that
Pea Plants
Factors
determine
traits
Some alleles are
dominant and
some
are recessive
Alleles are
separated
during
gamete
formation
independently
sorted during
Law of
Dominance
Segregation
Independent
Assortment

21. Section Analysis
THE LEGACY OF MENDEL
Section 11-1
So what did Mendel mean by some traits are dominant and some are recessive?
What did he believe controlled these traits?
Why did traits that seemed to “disappear” show up again in the F2 generation?
What happens to alleles during gamete formation that might explain this?
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22. Modern Genetics Has 3 branches Mendelian (Classical) genetics
Molecular genetics
Population genetics

23. Classical genetics
Focuses on the transmission of genes between generations
Punnett square are used to make predictions

24. Molecular genetics
Looks specifically at the genes involved in inheritance
It is concerned with the chemical make-up and control of genes

25. Population Genetics
Examines the genetic variation within and among populations
Such as determining why some individuals within a species exhibit different traits or change over time
Example: Albino animals