Dominant Genetic Disorders: Inheritance Questions Explained

Could you please clarify your question regarding genetic issues?

I have an autosomal dominant genetic disorder, but my parents and younger brother are normal.
I would like to ask: 1.
Will my brother's offspring inherit the autosomal dominant disorder or not? 2.
If my offspring have a 1/2 chance of inheriting the dominant disorder, and if they are normal, will their offspring still have a chance of inheriting the autosomal dominant disorder or not? Thank you.

Jiahao, 20~29 year old female. Ask Date: 2009/05/24

Dr. Xu Shanjing reply Rare Disease

Jiahao; autosomal dominant genetic disorders are typically inherited from parents, but a significant proportion can also arise from de novo mutations.
The symptoms of patients with certain diseases caused by dominant gene mutations can vary greatly (i.e., there can be significant phenotypic variability).
To determine whether the parents carry the mutated gene, molecular genetic testing is more reliable than merely assessing surface symptoms.
Your brother appears normal, so the likelihood of his children being normal is quite high, but to be completely certain, it is essential to confirm the absence of gene mutations.
Once a gene mutation occurs, the dominant disorder will be inherited by the next generation with a 50% chance.
Individuals who are asymptomatic and do not carry gene mutations will not pass these on to their children.
Since I am unaware of your specific condition, I can only provide this information.
Please feel free to reach out if you have further questions.
Xu Shanjing

Reply Date: 2009/05/24

More Info

Understanding dominant genetic disorders is crucial for assessing inheritance patterns and potential risks for future generations. In your case, it appears that you have a dominant genetic disorder, while your parents and brother do not exhibit the condition. This situation raises important questions about the inheritance of such disorders.

1. Will your brother's children inherit the dominant genetic disorder?
Since your brother does not have the dominant genetic disorder, he does not carry the mutated gene responsible for the condition. Dominant disorders require only one copy of the mutated gene for the individual to express the disorder. Therefore, your brother's children will not inherit the disorder from him, as he is not a carrier of the gene. The risk of your brother's children inheriting the disorder is effectively zero.

2. What about your children?
As you mentioned, if you have a dominant genetic disorder, there is a 50% chance that each of your children will inherit the disorder. This is because you have one normal allele and one mutated allele. If a child inherits the mutated allele, they will express the disorder; if they inherit the normal allele, they will not.
If you have a child who is unaffected (normal), it is important to note that this child has a 50% chance of being a carrier of the mutated gene. This means that while they do not express the disorder, they could pass the mutated gene to their own children. If your unaffected child has children, there is a possibility that they could pass on the dominant gene, leading to a 50% chance that their children could express the disorder if they inherit the mutated allele.

In summary, your brother's children will not inherit the dominant genetic disorder since he does not carry the gene. However, your children have a 50% chance of inheriting the disorder from you. If they are unaffected, they could still be carriers, which means they could potentially pass the disorder to their own children.

Additional Considerations
It is also worth noting that dominant genetic disorders can exhibit varying degrees of penetrance and expressivity. This means that even if a child inherits the mutated gene, the severity of the disorder can differ significantly among individuals. Some may exhibit mild symptoms, while others may have more severe manifestations.

For families dealing with dominant genetic disorders, genetic counseling can be invaluable. A genetic counselor can provide personalized risk assessments, discuss the implications of genetic testing, and help families understand their options for family planning. If you are considering having children and are concerned about the risk of passing on a genetic disorder, consulting with a genetic counselor can provide clarity and support.

In conclusion, understanding the inheritance patterns of dominant genetic disorders is essential for making informed decisions about family planning and managing potential risks for future generations.

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