What is one of the key characteristics of mRNA compared to DNA?

The key characteristic that distinguishes mRNA from DNA is that mRNA contains uracil instead of thymine. In the genetic code, DNA uses thymine as one of its four bases: adenine, thymine, cytosine, and guanine. However, in RNA, thymine is replaced by uracil, which pairs with adenine during processes such as transcription and translation.

This replacement is significant because it reflects the different roles these nucleic acids play in the cell; DNA primarily serves as the genetic blueprint, while RNA, particularly mRNA, serves as a messenger that transmits the instructions encoded in DNA for protein synthesis. Understanding this difference is crucial for grasping how genetic information is expressed in living organisms.

The other options do not accurately describe characteristics that are true for mRNA: mRNA is single-stranded, it is generally less stable than DNA, and it can indeed leave the nucleus to facilitate protein synthesis in the cytoplasm, highlighting its role as an intermediary in gene expression.