DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the two types of nucleic acids found in cells. Nucleic acids, in turn, are the biological molecules that code for genetic information and proteins. Here is a comparison of the similarities and differences between DNA and RNA.
Similarities Between DNA and RNA
As nucleic acids, DNA and RNA share some similarities:
- Both DNA and RNA store genetic information.
- DNA and RNA are both large biological polymers.
- Both DNA and RNA consists of sugar, nitrogenous bases, and a phosphate backbone.
- On both molecules, guanine and cytosine pair with each other (are complementary).
- Complementary base pairs are connected by hydrogen bonding. Two hydrogen bonds form between adenine and either thymine or uracil, while three hydrogen bonds form between cytosine and guanine.
Differences Between DNA and RNA
DNA and RNA are different from each other in several ways.
- DNA uses the sugar deoxyribose, while RNA uses the sugar ribose. The difference between deoxyribose and ribose is that deoxyribose has a hydrogen (-H) attached to the second (2′) carbon of the sugar ring, while ribose has a hydroxyl group (-OH) attached to this carbon.
- Usually, DNA is a double-stranded molecule that forms a double helix, while RNA is a single stranded molecule. Rarely, DNA takes other forms, such as triple-strand DNA and quadraplex DNA. Similarly, double-stranded RNA (dsRNA) occurs in some viruses.
- DNA uses the bases adenine, thymine, guanine, and cytosine. RNA uses the bases adenine, uracil, guanine, and cytosine. Uracil differs from thymine in that it lacks a methyl group.
- DNA and RNA serve different functions. DNA stores and transfers genetic information, while RNA acts as a messenger between DNA and ribosomes to make amino acids and proteins. Viruses use either DNA or RNA as genetic material, but they require the hosts cellular machinery to replicate. Sometimes RNA acts as a catalyst for biochemical reactions.
- RNA is less stable than DNA and is more vulnerable to mutation and attack than DNA. DNA is protected by proteins and has several repair mechanisms.
| Comparison | DNA | RNA |
| Name | Deoxyribonucleic acid | Ribonucleic acid |
| Function | Long-term storage of genetic information; transmission of genetic information to make other cells and new organisms. | Used to transfer the genetic code from the nucleus to the ribosomes to make proteins. RNA is used to transmit genetic information in some organisms and may have been the molecule used to store genetic blueprints in primitive organisms. |
| Structural Features | B-form double helix. DNA is a double-stranded molecule consisting of a long chain of nucleotides. | A-form helix. RNA usually is a single-strand helix consisting of shorter chains of nucleotides. |
| Size | DNA is a very long molecule, which would be several centimeters long if unravelled. | RNA molecules display variable length, but are much shorter than DNA. A large RNA molecule is only a few thousand base pairs long. |
| Composition of Bases and Sugars | deoxyribose sugar phosphate backbone adenine, guanine, cytosine, thymine bases | ribose sugar phosphate backbone adenine, guanine, cytosine, uracil bases |
| Location | DNA is found in the nucleus and within mitochonria. | RNA is mostly found in the cytoplasm. |
| Propagation | DNA is self-replicating. | RNA is synthesized from DNA on an as-needed basis. |
| Base Pairing | AT (adenine-thymine) GC (guanine-cytosine) | AU (adenine-uracil) GC (guanine-cytosine) |
| Reactivity | The C-H bonds in DNA make it fairly stable, plus the body destroys enzymes that would attack DNA. The small grooves in the helix also serve as protection, providing minimal space for enzymes to attach. | The O-H bond in the ribose of RNA makes the molecule more reactive, compared with DNA. RNA is not stable under alkaline conditions, plus the large grooves in the molecule make it susceptible to enzyme attack. RNA is constantly produced, used, degraded, and recycled. |
| Ultraviolet Damage | DNA is susceptible to UV damage. | Compared with DNA, RNA is relatively resistant to UV damage. |
| Stability | DNA is more stable than RNA and resists alkaline conditions. | RNA is more reactive than DNA and is not stable in alkaline conditions. |
Types of DNA and RNA
There are different types of DNA and RNA. DNA occurs in five forms: A-DNA, B-DNA, C-DNA, D-DNA, and Z-DNA. The B form occurs in most organisms and is a right-handed helix with a major and minor groove. The main types of RNA are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). Many additional types of RNA also exist. A cell typically contains one type of DNA and several forms of RNA.
RNA vs DNA Worksheet
Quiz students (or yourself) on your understanding of the differences between RNA and DNA:
References
- Burge, S.; Parkinson, G.N.; Hazel, P.; Todd, A.K.; Neidle, S. (2006). “Quadruplex DNA: sequence, topology and structure”. Nucleic Acids Research. 34 (19): 5402–15. doi:10.1093/nar/gkl655
- Whitehead, K.A.; Dahlman, J.E.; Langer, R.S.; Anderson, D.G. (2011). “Silencing or stimulation? siRNA delivery and the immune system”. Annual Review of Chemical and Biomolecular Engineering. 2: 77–96. doi:10.1146/annurev-chembioeng-061010-114133