1. Heredity = the passing of characteristics from parent to offspring
Genetics Ch. 9.1 (p )
Genetics = studying how characteristics are passed from parent to offspring
Heredity = the passing of characteristics from parent to offspring
Trait= a specific characteristic
Hair color, eye color, diabetes…

2. Genetics Ch. 9.1 (p.165-169) Example: complete the table
Mendel used pea plants that were pure strains for 1 of 2 traits
He compared 7 characteristics (table 9.1 p. 167)
P = pure strain; Pgreen= pure green seeds, Pyellow=pure yellow seeds…
Characteristic
Possible Trait 1
Possible Trait 2
Seed color
Seed texture

3. Generation = group of offspring born about the same time
Genetics Ch. 9.1 (p )
Generation = group of offspring born about the same time
Filial generation = offspring from crossing 2 different strains
F1 generation = offspring of first cross
F2 generation = offspring of second cross…

4. Genetics Ch. 9.1 (p.165-169) Characte ristic 1st Crossing
F1 generation results
(1st crossing)
F2 generation results
(2nd crossing)
Seed color
Pyellow X Pgreen
Pyellow X Pgreen = F1 seed color
100% yellow,
0% green
F1yellow X F1yellow = F2 seed color
75% yellow,
25% green
Seed texture
Psmooth X Pwrinkled
Psmooth X Pwrinkled = F1 seed tex
100% smooth,
0% wrinkled
F1smooth X F1smooth = F2 seed tex
75% smooth,
25% wrinkled
Flower color
Ppurple X Pwhite
Ppurple X Pwhite = F1 flower color
100% purple,
0% white
F1 purple X F1 purple = F2 seed color
75% purple,
25% white

8. Genetics Ch. 9.1 continued (p.168-169)
Mendel’s Conclusions:
Conclusion of 3:1 = Mendel realized that some factor was controlling the results
F1 generation 100% : 0%
F2 generation 75% : 25% or 3:1
Remember, 1850s, so Mendel does not know about DNA

10. Genetics Ch. 9.1 continued (p.168-169)
Allele = one possible gene for a given trait
Yellow seed allele and green seed allele
Gametes (sex cells) have only half the chromosomes
When gametes combine, the offspring gets 2 alleles for each trait
1 from each parent

12. Genetics Ch. 9.1 continued (p.168-169)
Dominant allele = allele whose trait is always expressed when allele is present
Recessive allele = allele whose trait is only expressed if a dominant allele is not there to block it
Law of independent
Assortment =yellow seeds can be wrinkled so Mendel concluded that traits aren’t linked
Not always true
Alleles close together on the same chromosome can move together

14. Genetics Ch. 9.1 continued (p.168-169)