Which statement is NOT true about discoveries from comparing DNA sequences across many species?

Which statement is NOT true about discoveries from comparing DNA sequences across many species?

• A. Organisms possessing a genetic code drastically different from that used by humans have been discovered.
• B. DNA sequences are highly conserved across related species.
• C. Some genes are shared among diverse organisms.
• D. Molecular similarities support evolutionary relationships.

Answer: (A)

DNA sequence comparisons show that the genetic code is essentially the same across life, which is why a claim of finding organisms with a drastically different code across many species isn’t supported. The code is nearly universal, reflecting a shared origin, with only a few specific, localized exceptions in mitochondrial genomes or a few unicellular lineages. These exceptions are not widespread enough to call the code drastically different across species. In contrast, DNA sequences are highly conserved among related species, meaning they remain similar over evolutionary time and help reveal relationships. Some genes are shared among diverse organisms because they perform essential cellular functions, so it’s common to find the same housekeeping genes across distant life forms. Molecular similarities—such as conserved gene sequences and structures—support evolutionary relationships and are the basis for building phylogenetic trees that group organisms by relatedness.

DNA sequence comparisons show that the genetic code is essentially the same across life, which is why a claim of finding organisms with a drastically different code across many species isn’t supported. The code is nearly universal, reflecting a shared origin, with only a few specific, localized exceptions in mitochondrial genomes or a few unicellular lineages. These exceptions are not widespread enough to call the code drastically different across species.

In contrast, DNA sequences are highly conserved among related species, meaning they remain similar over evolutionary time and help reveal relationships. Some genes are shared among diverse organisms because they perform essential cellular functions, so it’s common to find the same housekeeping genes across distant life forms. Molecular similarities—such as conserved gene sequences and structures—support evolutionary relationships and are the basis for building phylogenetic trees that group organisms by relatedness.