Final answer:
While the genetic code for protein synthesis is nearly universal across species, non-coding DNA sequences vary significantly among different species. Some non-coding sequences are conserved due to their functions in regulation and maintaining chromosomal structure.
Step-by-step explanation:
In considering the presence of non-coding DNA sequences among all living organisms, we can affirm that there are indeed some non-coding elements that are universally shared. However, the extent and specific sequences of non-coding DNA vary significantly among different species. While the genetic code for protein synthesis is nearly universal—with a few minor exceptions—in both prokaryotes and eukaryotes, the actual non-coding regions can be vastly different. For example, prokaryotes tend to have genomes with a higher percentage of coding DNA, while eukaryotes have larger portions of non-coding DNA, once thought to be 'junk DNA' but now recognized as having functions in regulation, DNA packaging, and chromosomal stability. Some of these non-coding regions are involved in producing small noncoding RNA molecules that regulate gene expression.
Thus, the correct answer to the student's question would most closely align with Option B: No, non-coding DNA sequences vary significantly among different species. However, it is important to recognize that while they vary, some conserved elements do exist, primarily related to regulatory functions or structural features of chromosomes.