DNA and RNA details topic

The Differences Between DNA and RNA

Compare and Contrast DNA and RNA

Genetic information is the basis for transferring traits from generation to generation. Living organisms use one of two molecule types for the transfer of genetic information. Deoxyribonucleic acid (DNA) is used in the vast majority of living creatures whereas ribonucleic acid (RNA) has a variety of functions within cells, as well as being used to carry genetic information in some viruses. Both DNA and RNA also have a variety of other functions within living creatures, including the generation of proteins within cells.

Structure of DNA

DNA is a polymer, which means it consists of many individual repeating molecular units. Each unit within DNA is called a nucleotide and consists of a 5-carbon sugar (deoxyribose), a nitrogen-containing molecule (also known as a base) and a phosphate group. Four different types of nucleotides exist and the only difference between these is the type of base attached to the sugar. DNA usually forms a double-stranded molecule. Each of the individual strands consists of a polynucleotide chain, and the two chains are linked by weak molecular bonds. The two strands wind around each other forming a twisted structure known as a double-helix.

Function of DNA

DNA is arguably the most important molecule within a biological organism. It is found within the nucleus of cells and is responsible for carrying the genetic code. DNA also controls the production of proteins within a cell. These biologically important molecules consist of chains of amino acids and are responsible for a vast number of functional activities within an organism. In DNA, a sequence of three bases corresponds to the production of an amino acid. Since a chain of amino acids is a protein, each segment of DNA, or "gene" is responsible for creation of a particular type of protein.

Structure of RNA

RNA is also a polymer but its constituent molecular building-blocks differ from that of DNA. RNA building blocks consists of a 5-carbon sugar (ribose as opposed to deoxyribose), a nitrogen containing molecule (also known as a base), a phosphate group, and a hydroxyl group. Hence the structural differences between DNA and RNA building blocks are due to the sugar and hydroxyl group. Unlike DNA, RNA is normally single chained. The chain folds in on itself producing a unique three-dimensional shape that depends on its sequence of bases.

Function of RNA

RNA has a number of essential functions within cells. During protein synthesis, the base sequences within DNA are transcribed onto single strands of RNA known as messenger RNA (mRNA). After transcription, these single strands of mRNA move to structures within the cell known as ribosomes. Within these structures another type of RNA, known as ribosomal RNA (rRNA), carries out protein synthesis by combining amino acids. Transfer RNA (tRNA) transports amino acids from various parts of the cell to the ribosomes and hence also aids in protein synthesis. Several other types of functional RNA, such as micro-RNA, play roles that are only now beginning to be understood, such as defense against viruses.

Summary of Differences Between DNA and RNA

1. DNA contains the sugar de-oxyribose, while RNA contains the sugar ribose. The only difference between ribose and deoxyribose is that ribose has one more -OH group than de-oxyribose, which has -H attached to the second (2') carbon in the ring.

1. DNA is a double-stranded molecule while RNA is a single stranded molecule.
2. DNA is stable under alkaline conditions while RNA is not stable.
3. DNA and RNA perform different functions in humans. DNA is responsible for storing and transferring genetic information while RNA directly codes for amino acids and as acts as a messenger between DNA and ribosomes to make proteins.
4. DNA and RNA base pairing is slightly different since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Uracil differs from thymine in that it lacks a methyl group on its ring.

Comparison of DNA and RNA

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.
Composition of Bases and Sugars	deoxyribose sugar phosphate backbone adenine, guanine, cytosine, thymine bases	ribose sugar phosphate backbone adenine, guanine, cytosine, uracil bases
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.

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