1. Question???
If two blue eyed people have kids, what color eyes will their kids have?
If two brown eyed people have kids, what color eyes will their kids have?
Have color sticks!

2. Genetics: Episode I A Monk, His Peas, and Genes
Ag Biology
Sutherlin AST

3. Genetics What is genetics? What is heredity? What are traits?
Branch of biology studying heredity
What is heredity?
Passing of traits from parent to offspring
What are traits?
Physical characteristics

4. Genetics Gregor Mendel A monk, 1800’s Austria
First to study and determine factors of heredity
Used carefully controlled experiments: only changed one factor at a time

5. Genetics Why peas? Produce sexually
Male and female parts on same flower
Male parts are called?
Female parts are called?

6. Genetics
Pollination – male sex cells (pollen) lands on female parts (pistil)
Fertilization – DNA from pollen combines with DNA from ovum (egg)
Becomes seed

7. Genetics
Self-pollination: male and female sex cells come from same plant
Cross-pollination: sex cells come from two different plants
Create hybrid

8. Genetics What did Mendel do?
Studied TALL traits and SHORT traits in plants (parents = P1)
Cross-pollinated these plants to get hybrids
ALL of the offspring (F1) were TALL

10. Genetics What did Mendel do next?
Took the offspring (F1), then crossed them together
This time, not all offspring the same.

12. Genetics What did Mendel do next? ¾ of plants were tall
¼ were short plants
This is called a 3:1 ratio

13. Genetics So what does this mean? Unit Factors
Mendel concluded two factors control each trait
We know these are genes
One factor from the mother
One from the father

14. Genetics Unit Factors For each gene, there are alleles
Different forms of each gene
Example: there is a gene for height (T)
It could be the Tall allele – T
It could be the Short allele - t

15. Genetics
Unit Factors
Since we have two copies of each gene, three combinations
Two Tall (TT) alleles
Two Short (tt) alleles
One Tall allele and one
short allele (Tt)
But how is this possible?

16. What else does this mean?
Genetics
What else does this mean?
Rule of Dominance
Only one allele is observable
Dominant alleles: observable trait
Recessive alleles: unobservable trait
So which is dominant for height in pea plants?

17. Genetics
So what does each look like?
TT:
tt:
Tt:

18. Genetics What about cows?
If you cross purebred black angus cattle with red angus cattle, you get black cattle
What does this mean?

19. Question:
You are growing peas. Use the chart of dominant and recessive genes.
You are crossing axial (AA) and terminal (aa) bud plants. What would the F1 generation be?
Would terminal or axial be more beneficial for the plant?

20. Mendel’s 7 Traits of Pea Plants

21. Genetics Two organisms can look the same, but carrying different genes
Phenotype: how an organism looks (think physical)
Tall? Short?
Genotype: the genes an organism has
Tall: could be Tt
Tall: could be TT

22. Genetics Homozygous – both alleles are the same
TT, tt
Heterozygous – alleles are different Tt
All of this, by a monk, in the 1800s!

23. Genetics Dihybrid cross
Looking at just one trait (height) is monohybrid (one)
But what if we track more than one trait?

24. Round Yellow X Wrinkled Green
Genetics
Mendel’s Dihybrid Cross
Round peas (R=round, r=wrinkled)
Seed color (Y=yellow, y=green)
Parents (P1)
Round Yellow X Wrinkled Green

25. Genetics Mendel’s Dihybrid Cross Parents (P1)
Round Yellow X Wrinkled Green
RRYY rryy
Result? Offspring (F1) ALL Round Yellows
RrYy

26. Genetics
Mendel’s Dihybrid Cross
F1 Cross X
So now what do you get?

28. Genetics Mendel’s Dihybrid Cross The point?
Law of Independent Assortment: genes for different traits are inherited independently of one another (green seeds do not have to be wrinkled!)

29. Genetics Punnett Squares
Tool for projecting Phenotypes and Genotypes of offspring
Developed by Reginald Punnett (England)

30. Genetics
Monohybrid Punnett Square

31. Genetics
Dihybrid Punnett Square