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Recessive Alleles
Takes two alleles to be expressed
Dominant Allele
Only takes one allele to be
expressed
Codominant Alleles
Both alleles contribute to physical
expression
Blood Type Genes
Multiple genes used to determine
blood type - called polygenic
Polygenic Traits
Traits that vary such as height,
hair color, or skin color use more
than two genes to determine.
Rh Blood Group
Rh stands for “rhesus monkey”
Rh Blood Group
Rh
Cross
+
-
+
++
+-
-
+-
--
Dominant: Rh+
Recessive: Rh-
ABO Blood Group
ABO alleles produce specific
antigens
Antigens: trigger an immune
response
ABO Blood Group
Possible Genotypes
Blood Type
Genotype
A
AA
AO
B
BB
BO
ABO Blood Group
Possible Genotypes
Blood Type
AB
Genotype
AB
O
OO
Blood Group Genes
Both ABO and Rh groups are
mentioned at the same time
Ex. AB- means AB blood type and
Rh-
Blood Group Problem 1
Could a man with type B blood
and a woman with type AB
produce a child with type O
blood?
Not possible
The children of a man
with type B blood and a
woman with type AB
blood could be type A,
type B, and type AB, but
not type O.
Blood Group Problem 2
What if the mother is type O+ and
the father is A-? What would the
offspring's blood type be?
A+, A-, O+, or O-
Blood Group Problem 3
If the mother of a child is blood type O+
and the child is A-, what blood type
would the father be? Does the Rh
factor of the child being - mean that
one of the parents has to be negative?
The father could be type A or type AB.
The father must be the source of the
A allele of the child.
The father of the child could be either
Rh+ (heterozygous with one Rh+
allele and one Rh- allele) or Rh(homozygous with two recessive Rhalleles).