Summary
Highlights
DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the only two types of nucleic acids. They are large organic macromolecules composed of nucleotide monomers.
Each nucleotide contains a phosphate group, a five-carbon sugar (pentose), and a nitrogenous base. DNA nucleotides have deoxyribose sugar, which has one less oxygen than RNA's ribose sugar.
DNA contains four nitrogenous bases: adenine (A), guanine (G), thymine (T), and cytosine (C). Adenine always pairs with thymine, and guanine always pairs with cytosine (the base pair rule).
Adenine and guanine are purines (double-ring structure), while thymine and cytosine are pyrimidines (single six-membered ring). Uracil, found in RNA, is also a pyrimidine.
RNA contains adenine, guanine, and cytosine, but instead of thymine, it has uracil (U). The presence of thymine indicates DNA, while uracil indicates RNA.
DNA nucleotides link through hydrogen bonds between their nitrogenous bases, forming a double-stranded molecule twisted into a double helix. This structure was first described by James Watson and Francis Crick in 1953, based on Rosalind Franklin's images.
Unlike DNA, RNA is always single-stranded. In eukaryotic cells, DNA is found only in the nucleus, while RNA can be found in both the nucleus and the cytoplasm.
DNA controls heredity by storing the genetic code for building proteins. RNA uses these instructions to synthesize proteins.
There are three main types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
mRNA copies instructions from DNA in the nucleus and carries them to ribosomes. Ribosomal RNA, along with proteins, forms ribosomes where the instructions are translated into proteins. tRNA brings specific amino acids to the ribosome to build the protein.
A concise recap highlighting the differences in sugar (deoxyribose vs. ribose), bases (thymine vs. uracil), and structure (double-stranded vs. single-stranded) between DNA and RNA, their cellular locations, and primary functions.