DNA and RNA for Students

DNA and RNA

DNA, RNA, and proteins are the three major informational macromolecules that are essential for life. DNA chemical named deoxyribonucleic acid is the genomic material in cells containing genetic information used in the development and functioning of all known living organisms. DNA is located in the nucleus, and a few can find in the mitochondria (mitochondrial DNA). Inside the nucleus of eukaryotic cells, DNA has organized into structures called chromosomes. DNA is the central repository of information for most animals and plants and even some viruses. The name comes from its structures, built of a sugar and phosphate backbone that is bonded by ester bonds as bases. So "deoxyribo" refers to sugar, and nucleic acid refers to the phosphate and bases. Bases are namely adenine (A), cytosine (C), thymine (T), and guanine (G).1

Figure 1: Schematic1

The DNA molecule consists of two strands that wind around one another to form a shape known as a double helix. These two strands run in an anti-parallel direction. The two strands are linked together by bonds between the bases; adenine bonds with thymine, and cytosine bonds with guanine. This sequence acts, as the genetic code, which subsequently specifies the arrangement of the amino acids within the proteins, and plays as instructions for assembling protein and RNA molecules. The ends of DNA strands are called the 5′(five prime) and 3′ (three prime) ends. The 5′ end has a terminal-phosphate group, and the 3′ end has a terminal-hydroxyl group. One of the crucial structural differences between DNA and RNA is the sugar, with the 2-deoxyribose in DNA replaced by ribose in RNA. The central dogma of molecular biology is that genes are made of the DNA and made into messenger RNAs, which are made into proteins and often expressed as “DNA makes RNA, RNA makes proteins, proteins make us”.2

Ribonucleic acid (RNA) is a molecule similar to DNA. RNA is a single-stranded molecule. An RNA strand has a backbone made of alternating sugar (ribose) and phosphate groups. Each sugar bonded with one of four bases- adenine (A), uracil (U), cytosine (C), or guanine (G). Different types of RNA exist in the cell with various applications- messenger RNA (mRNA) carries the genetic information that directs the synthesis of proteins. The protein synthesis process utilizes two more classes of RNAs, the transfer RNAs (tRNAs) and the ribosomal RNAs (rRNAs). The tRNAs are responsible for the delivery of amino acids to the ribosome, where rRNAs bond them together to form proteins.3

Reference:

1. National Human Genome Research Institute, Glossary of Genetic Terms, Deoxyribonucleic Acid (DNA). https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid

2. Thomas Jefferson University, Computational Medicine Center, DNA and RNA. https://cm.jefferson.edu/learn/dna-and-rna/

3. National Human Genome Research Institute, Glossary of Genetic Terms, Ribonucleic Acid (RNA). https://www.genome.gov/genetics-glossary/RNA-Ribonucleic-Acid

Figure 2: Schematic3