Final answer:
Comparing mitochondrial DNA (mtDNA) sequences within a biological family reveals that all siblings, regardless of sex, inherit the same mtDNA from their mother, and thus share identical mtDNA sequences.
Step-by-step explanation:
When comparing mitochondrial DNA (mtDNA) sequences from a person to members of their biological family, several statements about mtDNA inheritance can be considered. mtDNA is maternally inherited, which means it is passed from mothers to their offspring. Thus, the mother's mtDNA sequences would be identical to the mtDNA sequences of all her biological children. Therefore, biological siblings, regardless of their sex, would show the same mtDNA sequence if they share the same mother. This is because there is no recombination in mtDNA, and every person's mitochondria is a modified copy of their mother's mitochondria, altered only by the occurrence of rare mutations over time.
Accordingly, the correct answer would be that all biological siblings would show the same mtDNA sequence (Option B), assuming they share the same mother. Biological sisters would show identical mtdna sequences but biological brothers' mtdna sequences would be different (Option D) is not accurate because both brothers and sisters inherit the same mtDNA from their mother.