Incomplete DominanceNeither allele is dominant over the otherHeterozygous offspring have a phenotype that is somewhere between the two.

Incomplete Dominance

Incomplete DominanceHomozygous red parent: RRcrossed withHomozygous white parent: WW RR x WW yields heterozygous offspring RW that are pink

Incomplete Dominance

CodominanceBoth alleles contribute to the phenotype

Heterozygous offspring express both alleles

CodominanceX

Codominance: A black chicken crossed with a white chicken results in a speckled chicken

CODOMINANCE: ABO BLOOD TYPESBlood type depends on the presence or absence of certain carbohydrates on the surface of red blood cells3 alleles are possible:IAIBi

ABO BLOOD TYPESIA and IB are codominant to each other when they are paired.

i allele is recessive to both IA and IB

ABO Blood Groups

ABO Blood Groups

ABO Blood TypesBlood typing is actually far more complicated than A, B, and OABO are the MAJOR antigensThere are also MINOR antigensRh factor: + or -

ABO Blood Types

ABO Blood Types

ABO Blood Types

ABO Blood TypesWhy is it important to get the right blood type when getting a transfusion?Transfusion ReactionsImmune system (antibodies) will attack cells that have an antigen that the body doesnt recognize as self

Transfusion Reaction

Multiple Alleles

More than 2 possible alleles exist in a population

Multiple AllelesCoat color in rabbits: there are at least 4 different allelesC = full color (dominant to all other alleles)c (ch) = chinchillac (h) = himalayanc = albino (recessive to all other alleles)

Full color rabbit

Chinchilla rabbit: partial defect in pigmentation

Himalayan rabbit: color in only certain parts of body

Albino rabbit: no color; recessive to all other alleles

Polygenic Traits

Traits that are produced by the interaction of more than one different genes

Polygenic InheritanceFor example: coat color in Labrador retrievers is a result of interaction of 2 different genes.

Polygenic InheritanceExample: comb shape in chickens is a result of interaction between 2 different genes.

X-Linked InheritanceEarly 1900sThomas Morgans fruit fly studies

X-Linked Inheritance

X-Linked InheritanceMore than 300 human traits are X-linked.Most common X-linked recessive disorders:HemophiliaRed-green colorblindnessDuchenne muscular dystrophyAdrenoleukodystrophy (seen in the movie Lorenzos Oil)

BARR BODIESBarr body is found only in femalesIt is a darkly staining area in the nucleus of a cell that represents an inactivated X chromosomeOne X chromosome is randomly inactivated

Barr Body

Barr BodyDo you see the Barr body?

Barr Body: X inactivationCalico catGenerally all femalesHave one X chromosome coding for for gold color, and one X chromosome coding for black colorColor pattern shows how one X chromosome in each cell is randomly inactivated

Calico CatThere have been instances of male Calico cats foundHow could this happen?

Male Calico cat?HINT: Male calico cats are sterile

Male Calico cat?Answer: Male Calico cats have XXY chromosome configurationA Klinefelters cat? Yup, it happens.