Name______________________
PER__________
Date__________
This worksheet gives you practice in problems dealing with incomplete dominance. Below is a complete
example for you to follow.
Important information: With incomplete dominance R' is used to denote the recessive allele. Notice
the tick-mark above the R. It is used so that you can tell which kind of dominance is present in the
alleles. If it was simple dominance, then a small case letter would be used for the recessive allele.
EXAMPLE:
A certain flower expresses incomplete dominance in flower color.
The dominant trait is red (RR). The recessive trait is white(R'R'). The intermediate trait is pink.(RR').
Plant A: RR (red)
Plant B: R'R (pink)
Calculate the probability of each phenotype being passed down to the offspring.
INFORMATION:
R
R
Notice how the punnett square is set up so that one parent
has the genotype across the top.
R' R'R R'R
The other parent's genotype is down the side.
R RR
The table is filled in according to the corresponding
genotype.
RR
TOTALS:
RR (Red): 2 out of 4…… 2/4…….1/2
R'R (pink): 2 out of 4……..2/4……1/2
R'R' (white): 0 out of 4……0/4
Extension:
If the question asks for a ratio, you must do the following:
-Use the total for that phenotype.
-Write the ratio with the dominant 1st , intermediate 2nd and recessive 3rd ….or you can label the number.
Ratio for above problem: 2:2:0
Ratio for above problem: 2RR : 2R'R : 0R'R'
Practice:
1.) A pink flower is crossed with a white flower.
Calculate the probability of each phenotype being passed down to the offspring.
TOTALS: (percent and ratio)
RedRR:
Pink R'R:
White R'R':
2.) An alien animal can have long arms (LL), intermediate arms (L'L), or short arms (L'L').
Calculate the probability of each phenotype being passed down to the offspring.
Parent A: L'L (intermediate)
Parent B: L'L (intermediate)
TOTALS: (percent and ratio)
LongLL:
Intermediate L'L:
Short L'L':
3.) Aliens can be Blue, Green , or yellow.
Blue: BB
Green: B'B
Yellow: B'B'
Calculate the probability of each phenotype being passed down to the offspring.
Parents: Blue Alien mates with a Green Alien
TOTALS: (percent and ratio)
BlueBB:
Green B'B:
Yellow B'B':
4.) What distinguishing phenotype tells you that the inheritance is incomplete dominance?