Story 06 · Genes and medicine
The test that families can choose to take, or not
Huntington's disease is caused by a repeated stretch of DNA in one gene, each child of an affected parent has a 50% chance of inheriting it, and the gene's discovery in 1993 gave families a hard choice about testing.
- Huntington's disease
- Lake Maracaibo, Venezuela, and worldwide
- 1993
- 3 min read
On this page
Before you readWhat would you do?
Your cousin's father has Huntington's disease. You want to ask a free chatbot what your cousin's chances are, and plan to paste in the family's names and medical records. What is the better approach?
Pick an answer now. The file tells you whether you were right.
01The file in one minute
1The disease
Huntington's damages brain cells, usually starting in adulthood. There is no cure yet, though some symptoms can be treated.
2The gene
In 1993 researchers found it is caused by an expanded CAG repeat in the HTT gene, helped by Venezuelan families.
3The choice
Each child of an affected parent has a 50% chance. Adults can choose predictive testing after counselling, or not.
4The lesson for AI
Genetic data is very sensitive and affects relatives. Think before typing it into any app or chatbot.
02Timeline
1872
The American doctor George Huntington describes the disease.
1979
Nancy Wexler begins studies of families around Lake Maracaibo.
1993
Researchers identify the expanded CAG repeat that causes the disease.
Today
Predictive testing is offered with counselling, and research into treatments continues.
03The story
Huntington's disease damages nerve cells in the brain. Symptoms usually start in adulthood, often between the ages of 30 and 50, and include uncontrolled movements, problems with thinking, and changes in mood. It gets worse over many years, and there is no cure yet, though treatments can help with some symptoms.
The psychologist Nancy Wexler, whose mother had the disease, led long-term studies of large families living around Lake Maracaibo in Venezuela, where the disease is unusually common. Blood samples and family trees from thousands of people helped researchers find the gene. In 1993 an international group reported that the disease is caused by an expanded repeat of three DNA letters, CAG, in a gene now called HTT.
The condition is dominant: each child of a parent with the expanded gene has a 50% chance of inheriting it. Since the discovery, adults at risk can take a predictive test that shows whether they carry it, usually after counselling. Many people at risk choose not to be tested, and both choices are respected.
04What the science says
A predictive test for a disease with no cure raises questions that ordinary tests do not: how a person will live with the answer, who else it affects, and who might see it. That is why testing usually involves several counselling sessions, time to think and the right to change your mind.
The AI angle: genetic and health information is among the most sensitive data a person has. It can reveal facts about relatives too. Think carefully before typing it into any app or chatbot.
The idea behind this caseLesson: What not to paste into AI →
05What to take from it
- Respect each person's choice to be tested or not, including your relatives.
- Keep genetic test results private, and check who can see them before you share them anywhere.
- Do not paste genetic results or family medical histories into public chatbots.
- If Huntington's disease runs in your family, talk to a doctor or genetic counsellor before any test, so you can decide with support.
07 — Sources
- A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington's disease chromosomes · Cell · 1993-03
- Huntington disease · MedlinePlus Genetics, US National Library of Medicine · 2024
- Huntington's disease · NHS · 2024