Warm ups:
1. What is a sex linked disorder?
2. What chromosome are these genes usually
on? ( X or Y)
3. If you were a male, what two chromosomes
would you have?
a. XX
B. YY
C. XY
Incomplete dominance and Codominance in Genetics
Lets look at Incomplete
Dominance first!!!
Incomplete dominance is like the genes
sharing the dominance. You get a
mixing or blending of the dominant
trait.
Incomplete dominance
1. Incomplete dominance – when there are two
dominant traits that don’t have dominance over
each other. This results in a combined phenotype.
2.It’s like a “blending” of the two dominant genes,
both traits are expressed. (sharing dominance)
+
White
=
Red
Pink
Incomplete dominance
3. Examples:
a. Red flower color (R) and White flower color (W) = Pink
flowers (RW)
+
=
b. Red flowers (R) and Blue flower color (B) = Purple
flower color (RB)
+
=
c. When you have a purebred red; the genotype is RR
d. When you have a purebred white; the genotype is WW
e. When you have hybrid flower (RW) the resulting color is
PINK!! (both share dominance)
Examples of Incomplete Dominance
•
•
•
•
Skin color
Flower color
Fur color
Short fur or long fur
INCOMPLETE DOMINANCE PUNNETT SQUARES PRACTICE PROBLEMS
1. A red flowered is crossed with a white flowered . (R = red,
W = white)
R
RR
Red flower = _____
WW
White flower = ____
0
____ % white
0
____ % red
100
____ % pink
100
____ % heterozygous
0
____ % homozygous
R
W
WR
WR
W
WR
WR
2. A blue flowered rose is crossed with a purple flowered
rose. (B = blue, R = red)
B
BB
Blue flower = _____
BR
purple flower = ____
50
____ % blue
0
____ % red
50
____ % purple
50
____ % heterozygous
50
____ % homozygous
B
B
B B
BB
R
B R
B R
Now lets talk about Codominance in Genetics
In Co-dominance, you see both
dominance traits.
Co-Dominance
1. Co-dominance – when two dominant traits are
shown in the offspring.
2. Both traits appear at the same time, but not mixed
or blended together.
+
White
=
Red
+
=
Red and white
Co - dominance
3. Examples:
a. Example: Red flower color (R) and White flower color
(W) = Red and White flowers (RW)
+
=
b. Example: Yellow flowers (Y) and Blue flower color (B) =
Yellow and Blue flower color (YB)
+
=
Co - DOMINANCE PUNNETT SQUARES PRACTICE PROBLEMS
1. A red flowered is crossed with a white flowered . (R = red,
W = white)
R
RR
Red flower = _____
WW
White flower = ____
0
____ % white
0
____ % red
100
____ % red and white
100
____ % heterozygous
0
____ % homozygous
R
W
WR
WR
W
WR
WR
Exit slip
1. What type of dominance creates in a
blending or sharing of the genes?
2. What type of dominance creates an offspring
that shows both dominant traits.