Genetics Topics

How DNA becomes visible traits — from the structure of hereditary information to the emergence of the body itself.

01 · Structure

DNA Structure

DNA is a twisted ladder of base pairs — adenine always with thymine, guanine always with cytosine. This linear sequence of just four letters stores the complete blueprint of a living organism: three billion base pairs, coiled up inside every cell nucleus.

Beginner
DNA info page →
A T G C T A C G Sugar- phosphate Double helix — 4 bases, 1 code
02 · Inheritance

Mendelian Inheritance

Gregor Mendel discovered the rules of inheritance using peas: traits are passed on through alleles, of which every individual carries two. If one is dominant, it becomes visible — the recessive one stays hidden but is still passed on, and can reappear in the next generation.

Basics
Mendelian inheritance →
Parent 1 Parent 2 Aa Aa × A a A a AA Aa Aa aa Phenotype ratio 3 × dominant (visible) 1 × rec. Segregation ratio: 3 : 1
03 · Central Dogma

Transcription & Translation

DNA is first copied into a messenger RNA (transcription). This leaves the cell nucleus and is translated into a protein chain at the ribosome (translation). This path — DNA → mRNA → protein — is the central dogma of molecular biology, and it holds for every known living organism.

Intermediate
Transcription & translation →
Nucleus DNA Template Transcript. mRNA Export Ribosome Protein Translation
04 · Expression

Proteins as Building Blocks

Proteins are the working molecules of genes. As structural proteins (keratin) they form hair and nails; as pigments (melanin) they determine skin and hair color; as enzymes they drive metabolism. What a gene does depends on which protein it encodes and where that protein is active.

Intermediate
DNA construction kit →
Amino acid chain ··· Folding Protein Keratin Hair, nails Melanin Pigment, color Receptor Signals, vision One gene → one protein → one trait
05 · Regulation

Gene Regulation

Every cell in the body carries the same DNA — yet a skin cell makes different proteins than a nerve cell. Transcription factors bind to specific DNA sequences in front of a gene and switch it on or off. This fine-tuned control explains how a single cell can give rise to a hundred different cell types.

Advanced
Gene regulation →
Enhancer Promoter Gene TF Activator RNA Pol II mRNA Transcription factors control activity
06 · Epigenetics

Epigenetics

A second layer of information sits on top of the DNA sequence: methyl groups at CpG sites and modifications to histones switch genes off without changing the letter code itself. These markers can be altered by environment and experience — and some can even be inherited.

Advanced
Epigenetics →
Histone Octamer CH₃ Methyl CH₃ Gene: OFF Gene: ON No sequence change — only accessibility epigenetic switch
07 · Development

Developmental Genetics

How does a single fertilized cell become a body with a head, trunk, and limbs? Hox genes define along the body axis which segment becomes what. They are so fundamental that the same genes appear in flies, mice, and humans — and they always do the same job.

Complex
Developmental genetics →
Anterior Posterior Hox 1–3 Hox 4–6 Hox 7–9 Hox 10–12 Hox 13 Hox cluster Head Neck Thorax Abdomen Tail Hox genes — the universal blueprint of life