Heredity = the passing of characteristics from parent to offspring Genetics Ch. 9.1 (p.165-169) 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…

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  

Generation = group of offspring born about the same time Genetics Ch. 9.1 (p.165-169) 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…

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

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

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

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

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