1. Notes Chapter 11 Introduction to Genetics

2. 11-1: The Work of Gregor Mendel

3. Heredity is the passing of traits from parent to offspring.

4. Genetics is the scientific study of heredity.

5. Gregor Mendel
Austrian monk born in 1822 in the Czech Republic. worked with ordinary garden peas.

6. fertilization
Gamete – specialized cell involved in sexual reproduction.
Examples:
-Sperm (pollen)
-Egg

7. self pollination Single parent (true breeding).
Sperm/pollen fertilize the egg cells in the same flower.
The offspring are identical to the parent.

8. cross pollination Two parents.
Hybrid- cross of traits from different parents.

9. Gregor Mendel prevented self pollination by cutting off the male parts of the pea flower.
He cross pollinated by dusting the pollen from a selected flower onto the female part.

10. Trait
A specific characteristic, such as seed color or plant height.

11. Gene- Chemical factors that determine traits.
Allele- Different, contrasting, forms of a gene.
Example: The gene for plant height has two different alleles available…
T= tall
t = short

12. Principle of Dominance
Some alleles are dominant and others are recessive.
(Think of it like a card game… sometimes one card “trumps” another. They’re both good cards, but when played together… one is dominant.)

13. Dominant & Recessive Practice
Read the chart and determine which allele is dominant for….
-seed shape? -pod shape? plant height?
-seed color? -pod color?
-seed coat color? -flower position?

14. But what happens to the recessive allele? Does it just “disappear”?

15. This is what Mendel observed when he crossed the F1 generation….
The “short” allele reappeared in the F2 generation!
The “short” allele must have been present in the F1, however it was being “trumped out” & hidden by the dominant “tall” allele.

16. Segregation of Alleles (separation of alleles)

17. 11-2: Probability and Punnett Squares

18. The likelihood that a particular event will occur is called probability, by the “flip-of-a-coin”.
The principles of probability can be used to predict genetic crosses.

19. Punnett square T t TT Tt tt
A diagram that depicts the gene combinations from a genetic cross.
Alleles from one parent. T t TT Tt tt
Alleles from the other parent.
Possible combinations for offspring.

20. T t TT Tt tt homozygous – 2 identical alleles. (TT, tt)
heterozygous – 2 different alleles (Tt)
Practice:
Are the parents homozygous or heterozygous?
What percentage of the offspring will be homozygous? Heterozygous? T t TT Tt tt

21. T t TT Tt tt genotype – genetic make-up (letters, Tt)
phenotype – physical trait (what you see, tall) T t TT Tt tt

22. Genotype & Phenotype Practice
T= tall
t = short
If the genotype is TT, what will the phenotype be?
If the genotype is Tt, what will the phenotype be?
If the genotype is tt, what will the phenotype be?
If the phenotype is tall, what are the possible genotypes?
If the phenotype is short, what is the genotype?

23. 11-3: Exploring Mendelian Genetics

24. Beyond simple dominance…
- some alleles are neither dominant nor recessive…

25. …and many traits are controlled by multiple alleles or multiple genes

26. Incomplete dominance
One allele is not completely dominant over the other.
The phenotypes appear blended.

28. Codominance Both alleles contribute to the phenotype of the offspring.
The phenotypes are not blended… they both appear separately.

29. multiple alleles
Genes that have more than 2 alleles.

30. polygenic traits
Traits produced by the interaction of 2 or more genes (“having many genes”).

31. Drosophila fly – Thomas Hunt Morg

33. Other factors that can affect the phenotype of genes.
- climate, soil conditions, water