DNA, Genetics and Epigenetics

Chromosomes

A chromosome is a thread-like structure made of DNA and protein that holds genetic instructions. Think of it as a tightly packed package or an instruction manual inside your cells that tells your body how to grow and work. ¹

A double helix describes the structure of DNA. A DNA molecule is made up of two linked strands that wind around each other to resemble a twisted ladder in a helix-like shape. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T). The two strands are connected by chemical bonds between the bases: adenine bonds with thymine and cytosine bonds with guanine.

Humans usually have 46 total chromosomes arranged in 23 pairs inside almost every cell. You get one set of 23 chromosomes from your mother and the other set of 23 from your father. The final pair determines biological sex—females usually have two XX chromosomes and males usually have one X and one Y chromosome.

DNA methylation

DNA methylation is an epigenetic mechanism where a methyl group (CH₃) are added to DNA, altering gene activity without changing the underlying genetic sequence. Typically occurring at cytosine nucleotide base where it represses gene transcription, turning the gene off.

Lifestyle factors like diet, exercies, stress management, smoking and yoga can influence methylation. Nutrients including folate and vitamin B12 are also relevant.

The process is reversible where enzymes can remove methyl groups to reactivate genes.

Last updated on Sunday 26 July 2026 at 08:25 by administrators

1. National Human Geonome Research Institute (2026) National Human Geonome Research Institute – Nucleotide Available from: https://www.genome.gov/genetics-glossary/Nucleotide.