Introducing DNA and RNA
Are you sufficiently freaked out about genetics; and by extension, this power couple (DNA and RNA), what they are, what they do, and the implications of their activity? Most people get overwhelmed by genetics.
So fear not, here we are going to provide a simple introduction to the similarities between DNA and RNA and their differences, and then try to tie these to their functions and partnership.
This way, you will understand the basics before you attempt to delve into the complicated and detailed roles of each. Because of their intertwined fates in the form of the central dogma (Figure 1), we will discuss both the differences and similarities simultaneously.
The DNA and RNA Structures
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 consist of sugar, nitrogenous bases, and a phosphate backbone.
- On both molecules, guanine and cytosine pair with each other (are complimentary).
- 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 sugar deoxyribose, while RNA uses 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 quadruplex 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 host’s 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 of differences between DNA and RNA in tabular Form
|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 unraveled.||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|
adenine, guanine, cytosine, thymine bases
adenine, guanine, cytosine, uracil bases
|Location||DNA is found in the nucleus and within mitochondria.||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)|
|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.