A gene can exist in a variety of different forms, a condition explained by the term Multiple Alleles. Since only two copies of a gene exist in a cell, then only two alleles of any gene can be carried in an organism's genotype, regardless of how many alleles the gene may have. The classic example of multiple alleles is seen in human blood types of the A B O series. The phenotypes for this series are shown across the top. Determine the genotypes of these individuals and write them in the space below:
A phenotype =
B phenotype =
AB phenotype =
O phenotype =
Now click on the phenotype designations in the boxes on the right to see if your assumptions were correct.
Answer the following questions.
1.Is any allele dominant over any other allele in this series?
2. Is any allele recessive to any other allele in this series?
3. What sort of dominance is being displayed by this series of alleles?
Scroll down several lines for the answers.
ANSWERS:
1. None of the alleles are dominant as such. When A and B appear together, they display incomplete dominance since the phenotype is AB.
2. Type O is recessive to A and B. A is manifest whether or not the genotype is AA or AO. Similarly, the B phenotype is seen in both BO and BB genotypes.
3.These genes display incomplete dominance which is widely seen in multiple alleles. For more information click on the EYE COLOR button. To return to the allele study, click on the RETURN button.