Why some genetic traits appear and others remain hidden for generations

Science · Published 26 October 2026 Swipe more like this →

In short: You might carry a genetic blueprint for a condition without ever showing a single symptom. From extra fingers to serious metabolic issues, the way our bodies express inherited traits depends on a complex game of dominance and recessiveness played by our DNA.

Genetic disorders arise from mutations in the DNA sequence, which can manifest in various ways. Some are monogenic, caused by a single gene mutation, while others are multifactorial, involving multiple genes or environmental factors. Some disorders are present at birth due to inherited mutations, such as sickle cell disease, while others are acquired during a person's life through random chance or environmental exposures like cigarette smoke, which can lead to certain cancers.

The way these traits are passed down depends on alleles—different forms of a gene. In dominant inheritance, such as polydactyly (extra fingers or toes), an individual only needs one copy of the dominant allele from one parent to express the condition. In contrast, recessive inheritance, like cystic fibrosis, requires an individual to inherit two copies of the recessive allele. In these cases, parents can be 'carriers'—possessing one recessive allele but showing no symptoms—meaning they can pass the trait to their children without knowing they carry it.

Modern medicine offers tools to navigate these genetic risks, such as embryo screening. This process involves in-vitro fertilisation (IVF), where eggs and sperm are mixed in a lab. Embryos are grown to a few cells before one cell is removed for genetic testing. Only unaffected embryos, typically a maximum of two, are then placed back into the mother's uterus. However, this technology introduces significant ethical, social, and economic debates, particularly regarding the destruction of unused embryos and the high costs of the procedure.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Are your genes destiny or just a set of instructions for your body?
• Why having an extra finger is rare despite being a dominant trait
• Traits are not just genes; environment and history also shape what we pass on.
• Why your genetic code is not the same thing as your physical appearance
• The hidden logic of your DNA is a game of genetic alternatives
• Do male kangaroos actually possess nipples? The internet remains surprisingly ambiguous on this topic.
• Nature's vibrant colors often serve critical survival functions rather than mere aesthetic appeal.
• The Australian fish that survives months of drought by burying itself in dry sand
• How your body manufactures targeted weapons against external invaders
• Your body's heaviest organ is actually a complex, multi-layered shield
• How your body builds a personalized library of biological weapons
• The Greek Household Concept Explains How Organisms Interact With Their Environment

More in Biology · More in Science · Latest · A–Z · All topics