Multiple Choice
A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are __________.
13. Mendelian Genetics
Incomplete Dominance vs. Codominance
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You cross two true breeding lines of petunia. One produces red flowers and the other white flowers. The F1
offspring all show pink flowers. You conclude from this that:
A
Red is dominant.
B
White is dominant.
C
Red is incompletely dominant.
D
Red is incompletely recessive.
E
None of the answers listed above are correct.
Verified step by step guidance1
Identify the phenotypes of the parent petunia plants: one with red flowers and one with white flowers.
Recognize that the F1 offspring all have pink flowers, which is a blend of the red and white parental phenotypes.
Understand that incomplete dominance occurs when the heterozygous phenotype is an intermediate of the two homozygous phenotypes, rather than one being completely dominant over the other.
Conclude that the red flower trait is incompletely dominant because the F1 generation shows a blend (pink) rather than one of the parental phenotypes (red or white).
Therefore, the correct conclusion is that red is incompletely dominant, as the pink flowers in the F1 generation indicate a blending of traits.
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