1. The Origin of Modern Genetics6A

2. Objectives
I will be able to describe Mendel’s experiments with the genetics of peas.
I will be able to summarize the theories Mendel developed to explain the results of his experiments.
I will be able to differentiate between purebred and hybrid.
I will be able to explain the difference between dominant and recessive alleles.

3. Gregor Mendel
the father of genetics

4. (the study of inheritance)
Genetics
the study of how traits are passed from parents to offspring
(the study of inheritance)

5. the passing of traits from parents to offspring
Heredity
the passing of traits from parents to offspring
Trait: a genetically determined characteristic or condition

6. Gregor Mendel
Mendel's work was done about 140 yrs. ago, but even now much of what we know about genetics is based on Mendel's work and illustrated by it.

7. Gregor Mendel was born in 1822 on a farm in Heinzendorf, Austria
At age 21 entered the Augustinian order of the Roman Catholic Church
As a monk he - studied science at the University of Vienna and became an excellent mathematician

8. Gregor Mendel
As a school teacher - he engaged in many scientific activities
At a monastery - he began a program of selective breeding of peas. After 8 yrs. of raising 30,000 pea plants and recording and classifying many pages of notes, he wrote a paper with his conclusions called Mendelian Genetics (1865).

9. Mendel’s Experimental Methods
Mendel studied genetics by doing controlled breeding experiments with pea plants.
There are two types of pollination:
self-pollination
cross-pollination

10. Self-Pollenation

11. Mendel’s Experimental Methods
When a true-breeding (purebred/homozygous) plant self-pollinates, it always produces offspring with traits that match the parent.
Mendel cross-
pollinated pea
plants himself
and recorded
the traits that
appeared.

12. Cross-Pollenation

13. Mendel’s Results
Once Mendel had enough true-breeding plants for a trait he wanted to test, he cross-pollinated selected plants.
Plants are called hybrids if they come from true-breeding parent plants with different forms of the same trait.

14. First-Generation Crosses

15. Mendel’s Results hybrid
Science Use the offspring of two animals or plants with different forms of the same trait
Common Use having two types of components that perform the same function, such as a vehicle powered by both a gas engine and an electric motor

16. Mendel’s Results Mendel also cross-pollinated hybrid plants.
He observed that offspring of hybrid crosses always showed traits in a 3:1 ratio.

17. Second-Generation (hybrid) Crosses

18. Mendel’s Results
Mendel recorded traits of offspring from many hybrid crosses.

19. Mendelian Genetics
His paper was the first recorded study of how traits pass from one generation to the next.
Mendel also was the first to use the mathematics of probability to explain heredity.

20. Mendelian Genetics
When Mendel's paper was published, in 1865, it received little attention, and was rarely cited by botanists or biologists during the next 34 years.
In 1900, Mendel's work was cited by three botanists, writing in different parts of Europe: Hugo de Vries, in Amsterdam; Carl Correns, in Tübingen; and Eric Von Tcshermak, in Esslingen, Austria.

21. Mendel's Theories the concept of unit characteristics
the concept of dominant and recessive
the concept of segregation

22. the concept of unit characteristics
Mendel concluded that two factors, one from the sperm and one from the ovum, control each inherited trait.
if factors were the same - purebred TT (tall) tt (short)
if factors were not the same - hybrid Tt (tall)

23. Purebred / Homozygous
If an organism’s two alleles for a trait are the same, the organism is purebred for that trait.

24. Hybrid/ Heterozygous
If an organism’s two alleles for a trait are different, the organism is hybrid for that trait.

25. The Concept of Dominant and Recessive
Dominant trait - a genetic factor that blocks another genetic factor.
Recessive trait - a genetic factor that is blocked by the presence of a dominant factor.
The dominant allele (factor) completely masks the presence of the recessive allele (factor).

26. the concept of segregation
Mendel reasoned that when a cell forms gametes, the genes separate (segregate) so that there is only 1 gene for each characteristic in each gamete.

27. Principles of Heredity
Traits are controlled by alleles on chromosomes.
An allele’s effect is dominant or recessive.
When a pair of chromosomes separates during meiosis the different alleles for a trait move into separate sex cells.

28. Mendel's peas genetics - Experiments that changed the world.