Answer:
If a particular disorder is caused by a dominant allele of a single gene, then the following feature of the pedigree would allow one to conclude that the disorder is dominant:
If one of the parents has the disorder, and the offspring of that parent also have the disorder, then the disorder is likely caused by a dominant allele. In this case, the dominant allele would have a 50% chance of being passed on to each offspring, and therefore, approximately half of the offspring would be expected to have the disorder if it is caused by a dominant allele.
If the disorder were caused by a recessive allele, then it would only be expressed in individuals who inherit two copies of the allele (one from each parent). In this case, if one parent is a carrier of the recessive allele, then approximately 25% of their offspring would be expected to have the disorder if the other parent is also a carrier. If both parents have the disorder, then all of their offspring would be expected to have the disorder.
Therefore, by examining the pattern of inheritance of the disorder in a pedigree, one can often infer whether the disorder is caused by a dominant or recessive allele of a single gene.
Step-by-step explanation: