1. Chapter 11: Intro to Genetics
11-1
The Work of Gregor Mendel

2. Intro What is an inheritance?
Money or property left behind from a relative who has passed away.
Another form of inheritance has to do with your GENES!
Every living thing has a set of characteristics inherited from its parents or parent.
Genetics
What is an inheritance?
What is the scientific study of heredity called?

3. Gregor Mendel’s Peas Who was Gregor Mendel?
An Austrian monk who studied biological inheritance.
Born in 1822 in what is now the Czech Republic.
After becoming a priest, spent several years studying math and science.
Spent 14 teaching at the monastery high school. He was also in charge of the garden there. It was here that he did experiments with garden peas.
Who was Gregor Mendel?

4. Gregor Mendel’s Peas
Part of each flower produces pollen, which contains the plants male reproductive cells or sperm.
The female portion of the flower produces eggs.
During sexual repro, male & female repro cells in a process called fertilization.
Fertilization produces a new cell which develops into an embryo encased in a seed.
What did Gregor Mendel know about these pea plants?

5. Gregor Mendel’s Peas How do pea flowers reproduce?
They are self-pollinating, meaning that sperm cells in pollen fertilize the egg cells in the same flower.
The seeds produced by self-pollination inherit all of their characteristics from the single plant that bore them. They have a single parent.
When Mendel took charge of the monastery garden, he had true breeding plants. This means that if they were allowed to self-pollinate, they would produce offspring identical to themselves.

6. Pollination
Pea Flower (self-pollination)
Cross Pollination

7. Mendel’s Experiments What did Mendel want to do?
Mendel wanted to produce seeds by joining male & female repro cells from 2 different plants- (cross pollination). First he had to prevent self-pollination.
To do this, he cut away the male parts and dusted pollen from another plant onto the flower.
Produced seeds from 2 diff parents. This allowed Mendel to cross breed & study the traits.

8. Genes and Dominance How many traits did Mendel Study? What is a trait?
He studied 7 different traits on the pea plants.
A specific characteristic (seed color, plant height) that varies from 1 individual to another.

10. Genes and Dominance When describing plants what does “P” mean?
What does the “F1” represent?
The original pair of plants or the “parental” generation.
The offspring or “first filial.”
Filius and filia are the Latin words for son & daughter.
The offspring of crosses between parents with different traits are called hybrids.

11. Genes and Dominance
What were Mendel’s results? Did the characteristics of the parents blend in the offspring?
Not at all. All of the offspring had the characters of only one of the parents.
In each cross, the character of the other parent seemed to disappear.

12. Genes and Dominance
What were Mendel’s conclusions? (There were two conclusions).
What are different forms a gene called?
1st: Biological inheritance is determined by factors that are passed from 1 generation to the next. Today these “factors” are called genes.
Each of the traits Mendel studied was controlled by 1 gene that occurred in two contrasting forms. Ex: height: short and tall
They are called alleles (uh-LEELZ)

13. Genes and Dominance 2nd: Principal of Dominance
Some alleles are dominant & others are recessive.
Dominant allele will always be displayed.
Recessive allele will only be displayed when the dominant form is not present.
Mendel’s Exp: Tall (dominant), short recessive; yellow (dominant), green (recessive)

14. Segregation
How had the recessive alleles disappeared in Mendel’s experiments? Or were they still present in the F1 plants?
To answer this question, Mendel allowed all 7 kinds of F1 hydrid plants to produce an F2 (second filial) generation by self pollination.
He X the F1 generation with itself to produce the F2 offspring.

16. Segregation What did Mendel observe?
When Mendel compared the F2 plants, he found that the traits controlled by the recessive alleles reappeared! (1/4)

17. Explaining the F1 Cross
Why did the recessive alleles seem to disappear in the F1 and then reappear in the F2?
Mendel assumed that the dominant allele masked the recessive allele. However, the recessive allele showed up in some of the F2 plants.
At some point the allele for tallness had been separated from the allele for shortness.

18. Explaining the F1 Cross How did this segregation occur?
Mendel suggested that these alleles segregated from each other during the formation of gametes (GAM-eetz), or sex cells.

19. Explaining the F1 Cross
What happens to the alleles during segregation?
When each F1 plant flowers and produces gametes, the 2 alleles segregate from each other so that each gamete carries only a single copy of each gene. Therefore, each F1 plant produces 2 types of gametes, those with the allele for tallness and those with the allele for shortness.

20. Alleles segregate and are then paired up again when the gametes fuse during fertilization. Capital “T” represents the dominant allele. Lower case “t” represents the recessive allele. The F2 gen has a new combo of alleles.