Transcript Codominance and Mult alleles

Some traits do not have a clear
dominant & recessive allele.
B. In this case, BOTH alleles are expressed.
1. Example: Red flowers and White
flowers would produce Red & White
spotted flowers
C. This is called codominance because
BOTH alleles act like they’re dominant.
A.
1.
Cattle have red, roan, & white coat colors.
Roan is a “mixture” of the genes for red &
white.
a. There are three possible expressions of
this trait… what would the genotypes
be?
Red Cattle: RR
Roan bull: RW
White Cow: WW
b.
A roan bull is mated with a white cow.
What are the genotypes of the parents?
RW
P1=___________
c.
WW
P2=__________
What is the phenotypic ratio for the F1
generation?
R
W
W
RW
WW
W
RW
WW
2.
A red bull mated with a white cow
produces a roan calf.
a. What are the genotypes of the bull,
cow and calf?
RR
WW
RW
Bull_____
Cow_____
Calf_____
b.
What would be the probability of having
a RED calf if the two were mated
again?
0%
A.
Sometimes there are more than two
alleles possible for a trait.
1. However, each individual organism will still
only have two alleles (one from Mom and
one from Dad) even if there are more
2. Examples: blood types, hair color, and eye
color
B.
This can lead to more possible
genotypic and phenotypic ratios
1.
Human blood type is a good example
of BOTH multiple alleles and
codominance.
a. There are 3 possible alleles & two of them
act dominant (A and B are dominant while
o is a recessive allele)
2.
Blood Type Alleles
a. Type A: causes cells to make protein A for
the surface of the RBC’s
b. Type B: causes cells to make protein B for
the surface of the RBC’s
c. Type O: causes cells to make no proteins for
the surface of the RBC’s
3.
Both A and B alleles are DOMINANT over
the O allele because if any A or B allele
is present, they will be expressed and the
A or B proteins will be made
4.
Label the possible genotypes of the
following three phenotypes:
A
A
(RBC)
A
A
B
B
(RBC)
B
(RBC)
B
Phenotype:
A
B
O
Genotype:
AA, AO
BB, BO
OO
1.
Suppose a child is of blood group B
and its mother is of blood group O.
a. To what genotypic groups may the
father have belonged? AB, BB, BO
BO
b. The child?
c. The mother? OO
2.
A child has blood group AB. What 4
PHENOTYPIC blood type combinations
could its parents have?
1.
2.
3.
4.
A
Blood type______
A
Blood type______
AB
Blood type______
AB
Blood type______
x
x
x
x
B
Blood type_____
AB
Blood type______
B
Blood type______
AB
Blood type______
3.
A man has blood type A and his wife has
blood type B. A child is born with blood
type O. The man accuses his wife of
infidelity saying that this child could not
possibly he his. Do you agree or disagree?
Explain why.
Disagree both could be AO and BO, so
therefore both O alleles could be given to
child