Nucleic Acids

Structure and Types

Nucleic acids are large, complex organic molecules that contain the genetic information necessary for the biochemical functioning of cells.
They are made up of sub-units called nucleotides, each of which is composed of a sugar, a phosphate group and a nitrogenous base.
Two main types of nucleic acids are found in biological organisms: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

DNA is a long molecule that carries the hereditary information of an organism.
The structure of DNA is a double helix, which resembles a twisted ladder.
The backbone of DNA molecule is made of alternating sugar and phosphate groups, while the rungs of the ladder are made up of paired nitrogen bases.
There are four types of nitrogenous bases in DNA: adenine, thymine, cytosine, and guanine. Adenine pairs with thymine, and cytosine pairs with guanine, forming a stable base pair.

RNA usually exists as a single polynucleotide chain that is capable of folding into complicated structures.
Like DNA, RNA is made up of nucleotides. However, the sugar in RNA nucleotides is ribose, which has one more oxygen atom than the deoxyribose found in DNA nucleotides.
Also, instead of thymine, RNA has another nitrogenous base called uracil.
There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA), each with their unique role in protein synthesis.

DNA replication is the process by which a DNA molecule is duplicated, ensuring that each new cell has a complete set of DNA molecules.
It is a semi-conservative process, meaning each strand in the DNA double helix acts as a template to produce a new, complementary strand.
Enzymes such as DNA polymerase, DNA helicase, DNA ligase, and others play crucial roles in DNA replication.

The information in DNA is used to synthesize proteins in a two-step process – transcription and translation.
In transcription, the genetic information in DNA is copied into a mRNA molecule.
During translation, the sequence of nucleotides in mRNA is read by the ribosome to produce a specific protein.
The stretch of DNA that codes for a particular protein is known as a gene.

Genotype refers to the genetic constitution of an organism, while phenotype describes an organism’s observable characteristics, determined by its genotype and environmental influences.
Allele represents a variation of a gene, responsible for genetic diversity.
Mutation is a permanent alteration in the DNA sequence that can affect a gene’s function and potentially an organism’s phenotype.