DNA and RNA are two of the most important molecules that make up the human genome. The similarities between the two molecules are striking. While both are single stranded molecules, DNA has double strands of DNA that are linked together in tandem. RNA, on the other hand, has one strand and folds in on itself to link nucleobases together. RNA does not have double strands and folds into three-dimensional shapes, namely a hairpin loop. The role of RNA depends on the form of this loop.
Structure
DNA and RNA contain the same information in a different way. DNA contains a phosphate and sugar backbone and four nitrogenous bases (adenine, cytosine, guanine, and thymine) that are linked by hydrogen bonds. The four bases form the double helix, or ladder structure, of DNA. RNA molecules contain the same information, but are chain-jointed at phosphate and sugar molecules.
DNA has two chains, the left chain starting with a free phosphate group on top and the right chain beginning with a sugar molecule. Both chains end with a phosphate group on the bottom. RNA has the same pattern, but the left chain is longer than the right, and vice versa. This means that the strand on the left has more bases than the right. As a result, the DNA chains are antiparallel.
The phosphate groups of DNA and RNA are non-coplanar. This symmetry is a feature of DNA that makes it easier to fold. The distance between adjacent phosphorus atoms in DNA is approximately 0.11 nm. This characteristic greatly affects the helix shape. The helix of DNA is more than twice as long as it is wide. Thus, the distance between adjacent phosphorus atoms in DNA affects the shape of the helix.
Function
DNA and RNA are two molecules that carry genetic information. DNA carries the genetic information for proteins, while RNA carries it from the nucleus to the ribosomes. Both molecules are identical chemically, but the difference is in their structure. DNA is double-stranded, while RNA is single-stranded, with no complementary helices. RNA and DNA have different functions, including gene regulation and RNA interference. Small regulatory RNAs (sRNAs) carry out these functions.
Both DNA and RNA are made of ribose and deoxyribose sugars. Unlike DNA, RNA has a nitrogenous base, uracil, and a five-atom ring. Each base is paired with an adenine atom. Those two bases are essential to the process of making protein. DNA contains two strands, each containing four nitrogenous bases and one carbon atom.
mRNA contains information which is translated into a language of amino acids, which are building blocks for proteins. These amino acids are linked in a way that the cell’s protein-making machinery understands. In total, there are 20 types of amino acids, with different combinations of amino acids forming proteins. DNA was first discovered by Swiss biochemist Frederich Miescher in the late 1800s, but its structure was only discovered a century later.
Stability
The relative stability of DNA and RNA duplexes depends on their sequence. The d(AAATTT) and r(AAAUUU) dodecamers exhibit the lowest T m, and the mixed-sequence RNA duplexes are the most stable. The DDGDH of DNA nucleotides varies significantly as well, but they do not correlate with their stability.
The stabilisation and destabilisation of DNA and RNA is correlated by the differences in their A-tract structure. DNA and RNA have different types of stable and unstable dodecamers. The stabilising DG is GACUGAUCAGUC, whereas the destabilising DG is UUUAAA. DNA and RNA have a weak coupling at the r(TTTAAA) position.
The melting temperature of the duplex DNA is higher than that of RNA. The DNA melting temperature DH(DS) correlates with compensation temperatures for basepair opening. DNA melting temperature Tc increases with increasing cation concentration. RNA melting temperature is correlated with the H-D exchange, and the fractionation factors of imino hydrogens in DNA and RNA are much lower than unity. Several important factors contribute to the differences in thermodynamic stability between DNA and RNA.
The difference in the melting temperature between DNA and RNA is primarily due to the hydrogen bonding between the two molecules. DNA and RNA have helical structure and fold into internal bulges, basepaired stems, and hairpins. DNA and RNA are characterized by local structural fluctuation, which involves opening and closing of basepairs. The stability of DNA and RNA depends on a delicate balance between structural integrity and flexibility.