Multiple Choice
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:
13. Mendelian Genetics
Incomplete Dominance vs. Codominance
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A gene for the MN blood group has codominant alleles M and N. If both children in a family are of blood type M, which of the following situations is possible?
A
Each parent is either M or MN.
B
Each parent must be type M.
C
Both children are heterozygous for this gene.
D
Neither parent can have the N allele.
Verified step by step guidance1
Understand that the MN blood group system is determined by codominant alleles M and N, meaning both alleles are expressed equally in the phenotype.
Recognize that if both children have blood type M, they must have at least one M allele from each parent.
Consider the possible genotypes of the parents: MM, MN, or NN. Since the children are type M, the parents cannot both be NN.
Analyze the scenario where each parent is either M or MN. This means one parent could be MM and the other MN, or both could be MN, allowing for the children to inherit the M allele from each parent.
Conclude that the statement 'Each parent is either M or MN' is possible because it allows for the children to have blood type M, while the other options are not possible given the codominance of the alleles.
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