Genetics: DNA

DNA (Deoxyribonucleic Acid) is the genetic material that contains the information necessary for an organism’s growth, development, functioning, and reproduction.
DNA structure constitutes a double-helix shape model, discovered by scientists James Watson and Francis Crick. It is made up of two strands coiling around each other.
The basic building blocks of DNA are nucleotides which are composed of a sugar molecule (deoxyribose), a phosphate group and one of four types of nitrogen bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
The order, or sequence, of these bases forms the instructions in the genome. Human DNA consists of around 3 billion bases, and more than 99% of those bases are the same in all individuals.
The four bases pair up with each other to form, what are called, base pairs. Adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). This is known as complementary base pairing.
A ‘gene’ is a discrete sequence of DNA nucleotides. The position of a gene on a chromosome is referred to as its ‘locus’. Genes provide detailed instructions for cells and are responsible for specific character traits.
Genes are arranged in structures called chromosomes, which are located in the nucleus of cells. Humans have 23 pairs of chromosomes, making a total of 46.
Different versions of the same gene are called alleles. These cause variation in inherited characteristics like eye colour, hair colour etc.
DNA replication is a vital process that occurs before mitosis and ensures that each new cell has an identical copy of the DNA. This process involves the separation of the DNA strands, with new ones being formed alongside each one.
A mutation is a change that occurs in our DNA sequence, either due to errors when the DNA is copied or as the result of environmental factors. Some mutations can lead to genetic illnesses, while most mutations have no obvious effect.
The study of genetics involves examination and analysis of how these genes and mutations interact in the environment to produce specific characteristics in the organism.