Complex Patterns of Inheritance

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

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

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

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

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

Sex Linked Normal Female XAXA Carrier Female XAXa Affected Female XaXa 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

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

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

Blood Types Blood Type Blood Type That Can Be Received Type of Antigens Present Type of Antibodies Produced A ( IA ) A and O A antigens B antibodies B ( IB ) B and O B antigens A antibodies O ( i ) Universal Donor Only O No antigens A and B antibodies AB ( IAIB ) Universal Recipient All types A and B antigens No antibodies

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.

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