1. Why Do You Look Like You Do?
Genetics
Why Do You Look Like You Do?

2. What You Should Learn From This Presentation
You should know the definition of each of the bold, underlined words
You should know the general theme of the presentation
We will go over the presentation as a group, be prepared to discuss it

3. Genetics
Defined as the study of heredity.

4. History of Genetics 10,000 years ago, farmers in Egypt bred wheat
4,000 years ago, Asian horse breeders kept records of animal traits
Humans have been controlling the traits of crops and livestock since before the beginning of history

5. Gregor Mendel 1822-1884 Lived in Austria (now part of Czechoslovakia)
Was an Augustinian monk
Conducted breeding experiments in the monastery garden from
Published in 1866 (just after Darwin was published)
No one cared until 35 years later (about 1900)

6. Gregor Mendel
Experiment consisted of keeping amazingly accurate records of the garden pea
He chose the pea plant because he could get pure strains that had been produced over years by gardeners
The strains had many different varieties with contrasting traits
He planted and kept records of over 30,000 plants

7. Gregor Mendel’s Results
Trait
First Generation (F1)
Second Generation (F2)
Ratio
Yellow vs. Green Peas
All yellow
6022 Yellow 2001 Green ?
Round vs. Wrinkled Peas
All round
5474 Round 1850 Wrinkled
Inflated vs. Constricted Pods
All Inflated
882 Inflated 299 Constricted
Long vs. Short Stems
All Long
787 Long Stems 277 Short Stems
Colored vs. White Flowers
All Colored
705 Colored 224 White
Axial vs. Terminal Flowers
All Axial
651 Axial 207 Terminal
Green vs. Yellow Pods
All Green
428 Green 224 Yellow

8. Gregor Mendel’s Results
Did you see a trend?
What is the final F2 ratio for each of the traits?

9. Gregor Mendel’s Results
If you didn’t, go back and take a look again
Notice that the trait in the F1 generation is always the larger number in the F2 generation

10. Gregor Mendel’s Results
If you figured out the F2 ratio, you should have noticed something else
Almost all of them are close to 3:1

11. Gregor Mendel’s Results
Trait
First Generation (F1)
Second Generation (F2)
Ratio
Yellow vs. Green Peas
All yellow
6022 Yellow 2001 Green
3.01:1
Round vs. Wrinkled Peas
All round
5474 Round 1850 Wrinkled
2.96:1
Inflated vs. Constricted Pods
All Inflated
882 Inflated 299 Constricted
2.95:1
Long vs. Short Stems
All Long
787 Long Stems 277 Short Stems
2.84:1
Colored vs. White Flowers
All Colored
705 Colored 224 White
3.15:1
Axial vs. Terminal Flowers
All Axial
651 Axial 207 Terminal
3.14:1
Green vs. Yellow Pods
All Green
428 Green 224 Yellow
2.82:1

12. Gregor Mendel’s Results
Why did all of the F2 generations have a three to one ratio when the F1 generation were all one trait?
Because the pure parents each gave a gene or “factor” to each of the F1 offspring and one of those genes were dominant over the recessive gene

13. Gregor Mendel’s Results
Yet, some of those F1 generations passed on the the genes to their F2 generations

14. Gregor Mendel’s Results
The F2 generation must have had some of the traits from the P1 generation, but we were unable to see the recessive traits.
They were masked or covered by the dominant trait.

15. Mendel’s First Principle
Principle of Dominance and Recessivness
Each trait is controlled by a pair of factors (chromosomes)
The dominant factor masks or hides the recessive factor

16. Genotype vs. Phenotype
Genotype describes the genetic make-up of the organism
The actual genes
Phenotype describes the physical make-up of the organism
What traits does the organism show

17. Mendel’s Second Principle
The Principle of Segregation
Heredity factors are determined by distinct factors
For each trait, an individual carries two factors for each trait
The two factors of each trait segregate and end up in separate gametes

18. Mendel’s Second Principle
Today, those factors are called genes
Part of the DNA
Each gene codes for one trait
Those are called alleles

19. Mendel’s Second Principle
If you did the cross below, what is the probabilty of each genotype?

20. Monohybrid Cross
Tt x Tt T t TT Tt tt

21. Monohybrid Punnett Squares
Now you try some:
Tt x tt
Tt x TT
TT x tt