In humans, muscular dystrophy is a condition in which the muscles waste away during early life, resulting in death in the early teens. It is due to recessive sec-linked gene. A certain couple have 5 children- 3 boys, ages one, three and ten; and 2 girls, ages five and seven. The oldest boy show the symptoms of this disease. Suppose you are their family physician and they come to you for advice. What would you tell them about the chances of their other children developing the disease?
Since it is a recessive X-linked gene, the father definitely does not have the MD gene. Since the mother does not have MD, she is heterozygous. There is a 50% chance of the other boys getting the MD gene and the disease and a 50% chance of the daughters being carriers, but no chance of them having the disease.
Thank you :)
As the family physician, I would explain to the couple that muscular dystrophy is a genetic disease caused by a recessive sex-linked gene, which means it is carried on the X chromosome. This gene is responsible for the symptoms of the disease, including muscle wasting.
Since the couple has one affected boy, we can deduce that the mother must be a carrier of the recessive gene on one of her X chromosomes. As for the father, he cannot pass on the X chromosome to his sons since he only has a Y chromosome. However, he can pass on the X chromosome to his daughters.
To determine the chances of their other children developing the disease, let's analyze each child individually:
1. One-year-old boy: Since the one-year-old boy has not yet shown any symptoms, we cannot determine if he has the disease. However, if he inherited the recessive gene from his mother, he would be a carrier like her and could potentially pass it on to his future children.
2. Three-year-old boy: Similar to the one-year-old boy, we cannot determine if the three-year-old boy has the disease since he hasn't shown any symptoms yet. Again, if he inherited the recessive gene from his mother, he would be a carrier like her and could potentially pass it on to his future children.
3. Ten-year-old boy (affected): The ten-year-old boy already shows symptoms of the disease, which means he inherited the recessive gene from his mother. He will have a 50% chance of passing on the gene to his future daughters, who would then become carriers.
4. Five-year-old girl: Since the father can only pass on the X chromosome to his daughters, the five-year-old girl has a 50% chance of being a carrier like her mother.
5. Seven-year-old girl: Similar to the five-year-old girl, the seven-year-old girl also has a 50% chance of being a carrier like her mother.
It is important to note that being a carrier does not mean the child will develop the disease, but they could pass on the gene to their own children.
I would advise the couple that there is a possibility that their other children, particularly the boys, could be carriers of the gene. I would recommend consulting with a genetic counselor who can provide more detailed information on inheritance patterns, genetic testing, and potential risks for future pregnancies.