Complex Patterns of Inheritance

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:

Phenotypic Ratio:

Genotypic Ratio:

Parental Genotypes:

Cross a red snapdragon with a white snapdragon:

Phenotypic Ratio:

Genotypic Ratio:

Parental Genotypes:

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

Phenotypic Ratio:

Genotypic Ratio:

Parental Genotypes:

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

Cross a carrier female with a normal male

Phenotypic Ratio:

Genotypic Ratio:

Parental Genotypes:

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 TypeBlood 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

DonorOnly O No antigens A and B

antibodies

AB ( IAIB ) Universal Recipient

All types A and B antigens No antibodies

Blood Types

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 cB b