Final answer:
The probability that a child will have long earlobes when both parents have long earlobes depends on the parents' genotypes. If both are homozygous dominant, the probability is 100%; for heterozygous parents, it’s 75%. Further genotype information would be required to provide a definitive answer.
Step-by-step explanation:
If two individuals with long earlobes (a dominant autosomal trait) have a child, to determine the probability that their child will also have long earlobes, we would need to know the parents' genotypes. Since long earlobes are dominant, each parent could either be homozygous dominant (FF) or heterozygous (Ff). If both parents are homozygous dominant, the child will definitely have long earlobes, since they would inherit an 'F' allele from each parent, resulting in genotype FF. If both parents are heterozygous dominant (Ff), the chance that their child will also have long earlobes is 75% because the child could inherit an 'F' allele from either parent (genotype FF or Ff), with only 25% chance of inheriting two recessive 'f' alleles (genotype ff).
Without additional information, the probability cannot be 100% (unless you know both parents are FF), nor can it be 0%, because long earlobes are a dominant trait. Therefore, options b) 25% and c) 50% are not immediately correct, as there is a minimum 75% chance if both are heterozygous (Ff). This assumption aligns most closely with Mendelian inheritance patterns.