incomplete dominance
DESCRIPTION
Incomplete Dominance. Neither allele is dominant over the other Heterozygous offspring have a phenotype that is somewhere between the two. Incomplete Dominance. Incomplete Dominance. Homozygous red parent: RR crossed with Homozygous white parent: WW RR x WW - PowerPoint PPT PresentationTRANSCRIPT
Incomplete Dominance
Neither allele is dominant over the otherHeterozygous offspring have a phenotype that is somewhere between the two.
Incomplete Dominance
Incomplete Dominance
Homozygous red parent: RRcrossed with
Homozygous white parent: WW
RR x WW yields heterozygous offspring
RW that are pink
Incomplete Dominance
Codominance
Both alleles contribute to the phenotype
Heterozygous offspring express both alleles
Codominance
X
Codominance: A black chicken crossed with a white chicken results in a speckled chicken
CODOMINANCE: ABO BLOOD TYPES
Blood type depends on the presence or absence of certain carbohydrates on the surface of red blood cells
3 alleles are possible: IA
IB
i
ABO BLOOD TYPES
IA 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 Types
Blood typing is actually far more complicated than “A”, “B”, and “O”
ABO are the MAJOR antigens There are also MINOR antigens
Rh factor: “+” or “-”
ABO Blood Types
ABO Blood Types
ABO Blood Types
ABO Blood Types
Why is it important to get the right blood type when getting a transfusion? Transfusion Reactions
Immune system (antibodies) will attack cells that have an antigen that the body doesn’t 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 alleles C = full color (dominant to all other
alleles) c (ch) = chinchilla c (h) = himalayan c = 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 Inheritance
For example: coat color in Labrador retrievers is a result of interaction of 2 different genes.
Polygenic Inheritance
Example: comb shape in chickens is a result of interaction between 2 different genes.
X-Linked Inheritance
Early 1900’s Thomas Morgan’s fruit fly studies
X-Linked Inheritance
X-Linked Inheritance More than 300 human traits are X-
linked. Most common X-linked recessive
disorders: Hemophilia Red-green colorblindness Duchenne muscular dystrophy Adrenoleukodystrophy (seen in the
movie Lorenzo’s Oil)
BARR BODIES
Barr body is found only in females It is a darkly staining area in the
nucleus of a cell that represents an inactivated X chromosome
One X chromosome is randomly inactivated
Barr Body
Barr Body
Do you see the Barr body?
Barr Body: X inactivation
Calico cat Generally all females Have one X chromosome coding for for
gold color, and one X chromosome coding for black color
Color pattern shows how one X chromosome in each cell is randomly inactivated
Calico Cat
There have been instances of male Calico cats found How could this happen?
Male Calico cat?
HINT: Male calico cats are sterile
Male Calico cat?
Answer: Male Calico cats have XXY chromosome configuration A Klinefelter’s cat? Yup, it happens.