Complex Patterns of Inheritance

1. Complex Patterns of Inheritance

2. Incomplete Dominance • One allele does not over shadow the other, they mix together • Use RR, R’R, R’R’ • Ex. Carnations • A red carnation mated with a white carnation makes a pink carnation. • Ex. Snapdragons • Ex. Carnations

3. Cross a red snapdragon with a pink snapdragon: • Parental Genotypes: Phenotypic Ratio: Genotypic Ratio:

4. Cross a red snapdragon with a white snapdragon: • Parental Genotypes: Phenotypic Ratio: Genotypic Ratio:

5. Co-Dominance • Both alleles are expressed equally. One allele does not over shadow the other. • Use HRHR HRHW HWHW • Ex. Roan Cattle • Red and white hairs are present • Ex. Some flowers

6. Cross a roan cow with a roan bull • Parental Genotypes: Phenotypic Ratio: Genotypic Ratio:

7. Sex Linked • Traits that are carried on the X chromosome • Females need 2 recessive copies of the allele to express the trait, if they receive one they are a carrier. • Males only need one copy of the allele to express the trait, this is why sex linked traits are more prevalent in males. • Use X and Y chromosomes with the allele as a subscript to represent the trait • Normal Female • XAXA • Carrier Female • XAXa • Affected Female • XaXa • Normal Male • XAY • Affected Male • XaY

8. Cross a carrier female with a normal male • Parental Genotypes: Phenotypic Ratio: Genotypic Ratio:

9. Multiple Alleles & Co-dominance • In humans blood type is controlled by 3 alleles • A, B, O • A & B are co-dominant – O is recessive • Type O: OO or ii • Type A: • AA / IAIA(homozygous) • AO / IAi(heterozygous) • Type B: • BB / IBIB(homozygous) • BO / IBi(heterozygous) • Type AB • AB / IAIB

10. Blood Types

11. Multiple Alleles • Traits that are controlled by one gene with several different alleles. • Ex. Coat color in Labs is controlled by 4 different alleles, 5 coat colors are possible.

12. Polygenic Traits • Traits that are carried on more than one gene. • Exs: hair color, skin color, height. A a C c B b