More Genetics Problems- Incomplete Dominance, Codominance.
1. Snapdragons are flowers that come in both Red (R allele) and White (R’ alllele)
dominant colors. When the two are crossed they are incompletely dominant which
produces a “blended” color...pink (RR’ genotype).
(a) Show a Punnett square crossing a red snapdragon with a white one.
(b) Now, cross two of the F1 offspring from the previous cross and show what the
F2 outcome is (color and probability).
2. In chickens, F is the trait for frizzled feathers and S is the trait for straight
feathers. Since both are dominant, when they are inherited together, the result is
a “slightly frizzled” (SF) chicken.
Show Punnett squares for the following crosses:
(a) frizzled x straight feathers
(b) slightly frizzled x slightly frizzled feathers
(c) frizzled x slightly frizzled feathers
…for each of the above (a,b,c), indicate the expected probability (%) of each
potential phenotypic outcome in the offspring.
3. Roan is a name for cattle that show a heterozygous incomplete dominant
genotype. A roan calf's parents were a white cow and a red bull. What is a
roan's genotype? Can two roans mate and produce all roans? Explain using a
Punnett square as proof.
4. In humans, a disease called FH (familial hypercholesterolemia) is caused by an
incomplete dominance situation (inheriting both an F and an H allele).
If two heterozygous individuals married and planned to have children, what
information would you have for them concerning the possibilities of them having
normal children?