All cellular (living) organisms contain both DNA and RNA. Viruses, which are generally not considered to be living, contain one or the other.
Here are some major differences between RNA and DNA:
- With the exception of a few viruses, RNA is a single-stranded molecule while DNA is double-stranded. The two DNA chains are connected by hydrogen bonds between nitrogenous bases.
- DNA can is replicated during cell division; RNA is not.
- The function of DNA is the storage of hereditary material ― the "blueprints" of an organism and the proteins it synthesizes. The types of proteins determines traits of the individual. RNA functions in transferring DNA's code to the ribosomes where proteins are made.
- Both contain a sugar, phosphate groups, and four different nitrogenous base pairs. Three of the nitrogenous bases are the same for both RNA and DNA: guanine, adenine, and cytosine. Thymine, the fourth base pair found in DNA, is replaced by uracil in RNA.
- DNA has deoxyribose sugar while RNA has ribose sugar. The deoxyribose sugar has one less oxygen atom than the ribose sugar.
- DNA is longer than RNA because DNA contains all the genes of the organism and more besides. RNA is only long enough to code for a specific gene within DNA.
- In eukaryotic cells, DNA is only found in the nucleus while RNA can be found both in the nucleus and in the cytoplasm.
- Within one cell, there is only one type of DNA. However, there are three different types of RNA including:
- mRNA (messenger RNA) carries messages coded in DNA from the nucleus or nucleoid to the site of protein synthesis (ribosomes) in cytoplasm.
- rRNA (ribosomal RNA) is found in the structure of ribosomes, together with ribosomal proteins.
- tRNA (transfer RNA) transfers the amino acids from cytoplasm to the ribosomes according to the order of three nitrogenous bases (a codon) in mRNA.