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Types of Genetic Disease and How They Are Inherited

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  1. Autosomal Dominant Inheritance

    A condition appears even if only one parent passes down the abnormal gene. Huntington's disease is a well-known example of this inheritance pattern.

  2. Autosomal Recessive Inheritance

    A condition only appears if both parents pass down the abnormal gene. Parents can be symptom-free carriers of just one copy; cystic fibrosis and sickle cell anemia are well-known examples.

  3. X-Linked Inheritance

    The abnormal gene sits on the X chromosome, so the condition shows up more often in men, who have only one X chromosome. Hemophilia and red-green color blindness are well-known X-linked conditions.

  4. Chromosome Number Disorders

    These arise from having more or fewer chromosomes than normal. Down syndrome — trisomy of chromosome 21, meaning an extra copy — is the best-known example.

  5. Mitochondrial Inheritance

    Mitochondrial DNA is passed to children only through the egg cell, so related genetic conditions show a distinctive inheritance pattern — passed down only from the mother's side, never the father's.

  6. Genetic Counseling

    For families with a history of a genetic condition, genetic testing and professional counseling can help estimate the probability of a child inheriting the condition and plan ahead.

How Are Genetic Diseases Passed Down From Parents?

A genetic disease results from a mutation in a gene inherited from a parent, and the probability of passing it on to children varies considerably depending on the inheritance pattern. This page is general science and health education, not a substitute for medical diagnosis or treatment — if you're concerned about a family history of genetic conditions, consult a doctor.

Frequently Asked Questions

Can a genetic disease appear in a child even if both parents are healthy?

Yes. In autosomal recessive conditions, parents are often symptom-free carriers of just one copy of the gene, and a child born to two carriers can develop the condition.

Is Down syndrome caused by a genetic mutation in the parents?

Down syndrome isn't caused by a specific gene mutation — it results from having an extra copy of chromosome 21. Factors like parental age can influence the probability, but the parents don't need to carry any genetic abnormality themselves.