Merlin the magician is trying to impress his friend by crossing homozygous blue flowers with homozygous green flowers and producing brown flowers. Merlin’s friend is a geneticist, however, and is not impressed so she confronts him and explains it is not magic at all.
a) What kind of dominance would the friend say this is?
b) Draw a cross and Punnett square to show the inheritance (use the format shown in the text).
a) The friend would say this is an example of incomplete dominance.
b)
Cross: Homozygous blue (BB) x Homozygous green (GG)
Punnett square:
| B | B
---------|--------|--------
G | BG | BG
---------|--------|--------
G | BG | BG
The Punnett square shows that all the offspring will have the genotype BG, resulting in the production of brown flowers.
a) The friend would say that this is an example of incomplete dominance.
b) Cross:
Homozygous blue (BB) x Homozygous green (GG)
Punnett Square:
| B G
-------|-------
B | BB BG
-------
G | BG GG
Note: Brown is the result of mixing blue and green, so it is represented by the genotype BG.
a) The friend would say that this is an example of incomplete dominance.
b) To draw the cross and Punnett square, we need to assume that the blue flowers are homozygous for the blue color allele (BB) and the green flowers are homozygous for the green color allele (GG). Since the resulting flowers are brown, we can represent this color as a combination of the blue and green alleles.
Here is the cross:
Blue flowers (BB) x Green flowers (GG)
To create the Punnett square, we will write the possible gametes (sperm and ova) of each parent along the top and left-hand side of the square:
B B
-------------------
G | BG BG
-------------------
G | BG BG
The four boxes in the Punnett square represent the possible combinations of alleles that the offspring can inherit. In this case, all of the possible combinations result in the offspring having a combination of blue and green alleles, which produces the brown flower color.