What is the most likely mode of inheritance of the exceptionally rare condition represented in the pedigree below,and why?
A)impossible to determine,because the condition is so rare
B)recessive,because it is only present in one generation,but we do not have enough information to tell whether it's X-linked or autosomal
C)recessive,because unaffected parents have an unaffected child,and autosomal,because there are more autosomes than there are X chromosomes
D)X-linked recessive,because this would require the smallest number of rare alleles in the pedigree
E)X-linked recessive,because it only affects a male,and his parents are unaffected

Question

What is the most likely mode of inheritance of the exceptionally rare condition represented in the pedigree below,and why? 
A)impossible to determine,because the condition is so rare 
B)recessive,because it is only present in one generation,but we do not have enough information to tell whether it's X-linked or autosomal 
C)recessive,because unaffected parents have an unaffected child,and autosomal,because there are more autosomes than there are X chromosomes 
D)X-linked recessive,because this would require the smallest number of rare alleles in the pedigree 
E)X-linked recessive,because it only affects a male,and his parents are unaffected

Quizplus · Accepted Answer

X-linked recessive inheritance would require the smallest number of rare alleles in the pedigree, as only males are affected and their unaffected mothers must be carriers. Autosomal recessive inheritance would require two carriers to have an affected child, which is less likely given the rarity of the condition. Thus, X-linked recessive inheritance is the most likely mode of inheritance.

What Is the Most Likely Mode of Inheritance of the Exceptionally