Nucleic Acids

An Introduction to Nucleic Acid

Much like you would record your favourite songs on a tape in the 90s, so is our genetic information encoded in our cells, in the form of RNA and DNA. These are made of polymers of repeating units, with acidic properties. The term “nucleic acid” is used to describe these large molecules in our cells that hold so much vital information about us, our lineage and genetic setup.

Thus, nucleic acids are defined as large macromolecules that store, encode and transmit genetic data from one generation to another.

Let us find out more about nucleic acids and their structure and properties.

Nucleic Acids Structure

These vital macromolecules are typically made of oxygen, nitrogen, hydrogen, phosphorus and most importantly, carbon. They are long-chain polymers that consist of monomeric units called nucleotides. Each nucleotide comprises a phosphate group, a 5-carbon sugar and a specific nitrogen base. 

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In a nucleotide, if the sugar happens to be a ribose, then the polymer is called ribonucleic acid or RNA. Likewise, if the sugar is deoxyribose, it is called deoxyribonucleic acid or DNA. These are the most vital of all biomolecules present in living organisms. Found abundantly in all living organisms, they help encode, create and transmit the codex of genetic information of every cell in every organism. Furthermore, this encoded information is transmitted through the nucleic acid structure of DNA and RNA.

A string of nucleotides is bonded together to form the helical backbones of these nucleic acids. Typically, DNA consists of two such backbones while RNA consists of one. These further assemble into chains of base-pairs of nucleobases. Nucleobases are prominently of four types: adenine, guanine, cytosine, uracil and thymine. Note that uracil is found only in RNA while, thymine is present only in DNA.

Through a combination of several processes that include protein synthesis using amino acids, the sequences of these nucleobases allow nucleic acids like DNA to store and encode the body's genetic information.

Pop Quiz 1

  1. Which of these is a sugar group present in DNA?

  1. Ribose

  2. Thymine

  3. Deoxyribose

  4. Uracil

Nucleic Acids Types

As we mentioned earlier, there are two major types of nucleic acids commonly found in living organisms. These are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is the primary genetic material that is the source of all genetic information in living organisms. From the smallest unicellular bacteria to multicellular animals such as elephants and human beings, each of these contains DNA in their cells. DNA is also present in the nuclei of eukaryotes as well as in plants, in chloroplast and mitochondria.

Prokaryotic organisms, however, do not have their DNA enclosed in a membranous coat. In such organisms, the DNA is found freely-floating in the cytoplasm.

The genetic machinery of each cell, in its entirety, is known as a genome. The study of genomes, on the other hand, is known as genomics.

Activity: Find out from the Internet how each DNA or RNA strand in a cell is packed. Discuss it with your friends and teacher.

DNA Nucleic Acid

  • In combination with histone proteins, DNA forms a chemical complex called chromatin in the cells of eukaryotic organisms.

  • This, however, does not occur in prokaryotes.

  • Each chromosome of a living organism is a repository of thousands of hundreds of genes, dictating the organism’s identity, behaviour, habit and other functions.

  • Most genes contain the information that can code for protein products in the body. Some of these can also code for RNA products.

  • All cellular activity in cells is controlled by DNA.

Structure of DNA

  1. DNA consists of a double helix backbone made of two chains of polynucleotides.

  2. This double helix consists of two DNA strands, running parallel to each other.

  3. There exist hydrogen bonds between the helices, while the bases are contained in bundles within the helix.

  4. DNA is negatively charged, owing to the presence of phosphate groups.

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  1. The chemical composition of DNA consists of phosphoric acid, cyclic nitrogen bases and a pentose sugar.

  2. β-D-2-deoxyribose is the sugar molecule present in DNA molecules.

  3. The cyclic nitrogen bases found in DNA are adenine, guanine, thymine and cytosine.

  4. These bases play a key role in storage and transmission of genetic data, from the parent generation to the next.

Structure of RNA

RNA, in eukaryotic cells, mostly participates in synthesis of proteins and translation and transcription of genetic code. During transcription and protein synthesis, DNA molecules use an intermediate messenger RNA, also called mRNA to communicate with the entire cellular machinery, without leaving its place of origin. There are several other types of RNA which participate in protein synthesis. These are the microRNA, tRNA and the rRNA. In addition, the RNA is single-stranded and is often found to be in a folded state.

  1. Similar to DNA, RNA molecules also contain phosphoric acid, heterocyclic nitrogen bases and a pentose sugar group. 

  2. The heterocyclic bases found in RNA are guanine, adenine, cytosine and uracil. Unlike DNA, the sugar molecule present in RNA is a β-D-ribose, attached to phosphate groups.

Based on the functions they perform, RNA is of four different types. These are:

  • Messenger RNA: During the process of transcription, an RNA transcript is formed, which is also known as messenger RNA. The DNA uses this to communicate with all the other cells.

  • Micro RNA: The micro RNA is the smallest of all four types of RNA. It plays a very crucial role in gene expression and regulation.

  • Transfer RNA: Transfer RNAs participate in translation of the mRNA transcript produced during protein synthesis.

  • Ribosomal RNA: One of the most essential RNAs known, these are an integral component of ribosomes and help produce proteins in the body and our cells. 

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Nucleic Acids Function

Nucleic acids, mainly DNA and RNA, play an essential role in the bodies of living organisms. The functions performed by these are as follows:

  1. Nucleic acids help synthesise proteins in the body.

  2. The RNA is an especially important factor in the manufacturing of proteins.

  3. The DNA never leaves its place of origin but uses the RNA to act as an  intermediate to communicate with the rest of the cell.

  4. This intermediate mRNA enters the nucleus of the cell during the synthesis of proteins, and bonds with one of the DNA strands.

  5. The sequence of nitrogen bases in DNA is opposite to that of RNA, as they are complementary. This process is called transcription.

  6. For instance, if an RNA strand reads UUCCGGAA, then the DNA strand would read AAGGCCTT.

  7. Furthermore, the messenger RNA helps to transmit the code from the nucleus of the cell to the ribosomes. These are then assembled to form proteins.

  8. On reaching the ribosomes, the mRNA does not immediately set out to form proteins.

  9. In this step, the transferred RNA, also called the tRNA attaches itself to the mRNA, to translate the information carried by the mRNA into a readable form.

  10. This is done with opposite base pairings and in sets of three, also called codons.

  11. Thus each three-letter set can be a possible codon, encoding vital instructions and information.

  12. This correspondence is also known as the genetic code. It is present uniformly throughout all living organisms.

  13. The loss of nucleic acids, or DNA in cells, can be the cause for mutation and a variety of other diseases.

  14. DNA is a vital part of the fingerprinting method employed by forensic experts. Often used in matters of paternal disputes as well as criminal cases, the study of DNA is among the most flourishing fields of research, including evolution, anthropology, natural history and epidemiology.

Nucleic Acids Test

A nucleic acid test or NAT is a burgeoning technique used in medical science as well as other fields of molecular biology and research, to detect strains of unknown bacteria, viruses and other microbes. In this test, a particular sequence of nucleic acids is investigated and detected. This helps to identify or eliminate various strains of viruses and bacteria, or other pathogens in the blood. They are unique to the field of pathology, in the sense that, unlike most tests that detect antibodies or antigens, the NAT focuses more on the genetic components of the microbes.

This was a brief overview of nucleic acids, their structure and function. To learn more about the DNA and its many functions, as well as other key topics in molecular biology, stay tuned to our live demo classes, free PDF study material and reference notes. Download the Vedantu app today for easier access.

FAQ (Frequently Asked Questions)

1. What are the main components of nucleic acids?

Ans. A nucleic acid is a long-chain polymer made of monomeric units called nucleotides. A nucleotide, in turn, consists of three primary components. These are a phosphate group, a sugar molecule bonded to the phosphate group and a cyclic nitrogenous base. These nitrogenous bases can be of five types, namely adenosine, thymine, uracil, cytosine and uracil.

2. What is a nucleic acid?

Ans. Nucleic acids can be defined as large macromolecules that store, encode and transmit genetic information from one generation to another. These vital macromolecules are typically made of oxygen, nitrogen, hydrogen, phosphorus and most importantly, carbon. They are long-chain polymers that consist of monomeric units called nucleotides.

3. Which nucleic acids are present in viruses?

Ans. Viruses, usually have either DNA or RNA as their genetic material. These can be double-stranded or single-stranded.

4. What are the functions of nucleic acids?

Ans. Nucleic acids help synthesise proteins in the body. The RNA is an especially important factor in the synthesis of proteins. The DNA never leaves its place of origin but uses the RNA to act as an intermediate to communicate with the rest of the cell. DNA is a vital component of the fingerprinting method used by forensic experts.