- Gregor Mendel studied inheritance through experiments with pea plants and discovered that traits are passed from parents to offspring through discrete units called genes. - Mendel observed that traits can be dominant or recessive, and used mathematical probabilities to predict inheritance patterns in subsequent generations. - The concept of codominance was later introduced, where both alleles of a gene are expressed equally in heterozygotes rather than one being dominant. Blood type inheritance in humans follows codominance.

5. Genotype Symbol Genotype Vocabulary Phenotype TT homozygous DOMINANT or purebred tall tall Tt heterozygous or hybrid tall tt homozygous RECESSIVE or purebred short short

10. How can we predict these results? We complete the possible combinations. P p P P P p p p P P p p Homozygous-recessive Homozygous-dominant

11. These results show that all the F 1 (1 st filial generation) offspring are all purple colored hybrids. 100% purple offspring P P p Pp Pp p Pp Pp

12. P P P P p p p p P p P p We can use another Punnett square to predict the F 2 (2 nd filial generation) offspring. Heterozygous - hybrid Heterozygous - hybrid

13. P P P P p p p p P p P p The results are always mathematically the same, a 3:1 ratio with 75% purple & 25% white offspring Heterozygous - hybrid Heterozygous - hybrid Phenotypic ratio 3:1 Genotypic ratio 1:2:1

16. R W R R R W W W R R W W Homozygous Homozygous Codominance: F 1 generation

17. R W R R R W W W R R W W Codominance: F 1 generation 100% pink offspring

18. R R R R W W W W R W R W Heterozygous Heterozygous Codominance: F 2 generation

19. R R R R W W W W R W R W Heterozygous Codominance: F 2 generation A 1:2 :1 ratio with 25% red, 50% pink & 25% white offspring Heterozygous

20. I A I B I B I A I O I O I O I O I A I O I B I O Codominance: in humans Blood Type: phenotypic ratio 1:1:1:1 1 type A 1 type B 1 type AB 1 type O

21. Codominance: in humans Blood Type: A & B are equally strong. O is recessive. I A I O is Type A I B I O is Type B I A I B is Type AB I O I O is type O