Download Incomplete Dominance

Incomplete Dominance
Neither allele is dominant over the
other
Heterozygous offspring have a
phenotype that is somewhere between
the two.
 Red + White = ___________
Incomplete Dominance
 Homozygous red parent: RR
crossed with
Homozygous white parent: WW
RR x WW
yields heterozygous offspring
RW that are pink
 Red + White = ___________
Incomplete Dominance
Circle the Heterozygous Flowers
Incomplete Dominance
Circle the Homozygous Horses
Codominance
 Both alleles contribute to the phenotype
 Heterozygous offspring express both
alleles
Circle the word Codominance and underline the “Co” part of
the word. Co refers to together, jointly or mutually.
Codominance
X
What Color Will the Offspring Be?
Codominance: A black chicken crossed with a
white chicken results in a speckled chicken
How is this type of inheritance different from incomplete dominance?
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 :Type A Blood
 IB :Type B Blood
 i :Type O Blood
ABO BLOOD TYPES
 IA and IB are codominant to each
other when they are paired.
 i allele is recessive to both IA and IB
If mom has type is homozygous for type A blood and dad is
Homozygous for Type B blood, all of the offspring will have what
blood Type?
Which blood type has no antigens?
Which blood type has both antigens?
Blood will reject cells that have foreign antigens. Type A would
Reject type B and O would reject A and B and AB.
Which blood type do You think would accept all the other blood types?
ABO Blood Groups
Circle the square that shows type O blood.
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 “-”
Rhesus macaque.
Circle your blood type if you know it.
ABO Blood Types
Put a star next to the most common blood type.
Why is it surprising that type O is the most common blood
type?
ABO Blood Types
Laugh
ABO Blood Types
The blood type that can receive blood from any other Blood type is known as the universal donor.
Circle the blood type that is the universal donor. The universal receiver can accept blood from any
Donor, put a square around the universal receiver.
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 Alleles
 Coat 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
Which Chromosome doe you think X-linked traits are found on?
X-Linked Inheritance
X-Linked Inheritance
 More than 300 human traits are Xlinked.
 Most common X-linked recessive
disorders:




Hemophilia
Red-green colorblindness
Duchenne muscular dystrophy
Adrenoleukodystrophy (seen in the
movie Lorenzo’s Oil)
How many X’s does a male have _____, how many does a female have _____
Who do you think is more likely to have an X-linked disorder? Male or Female.
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 in each cell is
randomly inactivated
 How many active chromosomes are
found in the cells of a human female?
Barr Body
Barr Body
Do you see the Barr body?
Circle 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
Why do you think Calico Cats are usually all female?
Calico Cat Color Inheritance
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.