Final answer:
Codominance is when neither phenotype is recessive and the heterozygous individual expresses both phenotypes. A common example is the ABO blood group system.
Step-by-step explanation:
Codominance is when neither phenotype is recessive and the heterozygous individual expresses both phenotypes. A common example of codominance is the ABO blood group system, where individuals with both A and B alleles have type AB blood. Therefore, the correct answer is option D: multiple alleles and codominance.
Codominance is a form of genetic inheritance where both alleles are equally expressed in the phenotype, such as in the case of the AB blood type or MN blood groups. The correct answer to the student's question is C.) Straight, Straight & Curly, Curly, which illustrates both traits being visible in the phenotype.
The example of codominance in different phenotype possibilities is C.) Straight, Straight & Curly, Curly. This is because in codominance, both alleles are expressed at the same time, neither one being dominant over the other. Individuals who are heterozygous for a codominant trait will express both phenotypes, such as having both straight and curly hair. This contrasts with complete dominance, where one allele is expressed over the other, and incomplete dominance, where the heterozygous phenotype is intermediate between the two homozygous phenotypes.
For instance, the ABO blood group system is a classic example of codominance. The alleles for A and B blood types are both expressed in individuals with AB blood type. Another example is the MN blood groups of humans, where individuals with genotype LMLN express both M and N antigens on their red blood cells.