Which statement best describes DNA conservation and variation among organisms?

Which statement best describes DNA conservation and variation among organisms?

• A. All DNA sequences are identical across organisms
• B. DNA uses a different genetic code in bacteria
• C. All DNA has the same structure and uses the same code and transcription and translation processes. Among different organisms, the DNA sequences will vary because the organisms make different proteins.
• D. DNA is not universal; transcription is different

Answer: (C)

DNA is largely conserved in its basic form and in how genetic information is read and used. The chemical structure of DNA is the same across organisms—a double helix with a sugar-phosphate backbone and four bases (A, T, C, G). The genetic code that translates sequences of bases into amino acids is nearly universal, and the core steps of transcription (copying DNA to RNA) and translation (assembling proteins from RNA using the ribosome) are shared by almost all living things. Because organisms carry different genes and regulatory regions, their DNA sequences vary, leading to different proteins being produced and, consequently, different traits. Noncoding regions also contribute to regulation and expression, but the fundamental idea is that the code and the machinery are universal, while sequence differences generate diversity.

DNA is largely conserved in its basic form and in how genetic information is read and used. The chemical structure of DNA is the same across organisms—a double helix with a sugar-phosphate backbone and four bases (A, T, C, G). The genetic code that translates sequences of bases into amino acids is nearly universal, and the core steps of transcription (copying DNA to RNA) and translation (assembling proteins from RNA using the ribosome) are shared by almost all living things. Because organisms carry different genes and regulatory regions, their DNA sequences vary, leading to different proteins being produced and, consequently, different traits. Noncoding regions also contribute to regulation and expression, but the fundamental idea is that the code and the machinery are universal, while sequence differences generate diversity.