Final answer:
Incomplete dominance is when the phenotype of heterozygote offspring is an intermediate between the phenotypes of both homozygous parents because neither allele is completely dominant. This results in an offspring phenotype that blends both parental traits, such as pink flowers from red and white snapdragons.
Step-by-step explanation:
Incomplete Dominance in Genetics
During incomplete dominance, the phenotype of the heterozygote offspring is an intermediate of the phenotypes of both homozygous parents. This happens because no allele is completely dominant over the other. An example of this is seen in snapdragons, where the crossing of a homozygous red flower (CRCR) with a homozygous white flower (CWCW) results in offspring with pink flowers (CRCW). In this situation, the allele for red color is not fully dominant over the allele for white color, resulting in pink flowers due to the mixing of the two alleles' influences.
Another example of incomplete dominance can be seen in the fruit color of eggplants, where purple color is due to two functional copies of the enzyme, white is due to two non-functional copies, and with one functional copy, the resulting color is violet because there isn't enough purple pigment produced. This pattern of inheritance is significant because it allows the determination of an organism's genotype directly from its phenotype, which is not possible with complete dominance.
When two heterozygote organisms with incomplete dominance are crossed, they can produce offspring with a 1:2:1 phenotype ratio. This is in contrast to the traditional 3:1 ratio observed when one allele is completely dominant over the other.