Part 3: Diagnosis
“Could you please tell me about your
heritage?” asked Dr. Connors as he lifted his ophthalmoscope to Jade’s eye,
focusing at the center spot on the back of the retina.
“My husband and I are of Ashkenazi Jewish decent. We both grew up in a little neighborhood where the majority of the Ashkenazi Jews were located,” described Marissa.
“Are there any medical records in your family or your husband’s involving any diseases or conditions?” inquired Dr. Connors.
“Not that I can think of,” responded Marissa.
Dr. Connors nodded, placed down his ophthalmoscope and began scribbling notes in a little notebook. Marissa sat patiently, becoming anxious with every minute that passed by.
“Doctor, do you know what’s wrong with Jade?” asked Marissa.
Dr. Connors looked up at Marissa slowly and stared at her for what felt like hours. He got up, placing down his notebook and pen, and began pacing across the floor.
“Doctor, please, I’m worried. Do you know why my daughter is acting as she is?” pleaded Marissa.
Dr. Connors sighed, grabbed a seat and looked solemnly at Marissa.
“The eye examination shows that your daughter has cherry-red spots on the back of her retina. This is an indication of Tay-Sachs disease. Tay-Sachs disease is an autosomal recessive disorder that is genetically inherited. In order to have this condition, the individual must receive both copies of the recessive allele. This would mean that both you and your husband are carriers for this disease. Unfortunately, this disease is more common in the Ashkenazi population. Tay Sachs progressively destroys nerve cells in both the brain and the spinal cord. This would explain the odd symptoms that your daughter has been exhibiting recently. Sadly, there is no cure for Tay-Sachs, and it progresses to stages where the infected individual experiences seizures, vision and hearing loss, intellectual disability, paralysis and death,” explained Dr. Connors as he rubbed his eyes, “I’m very sorry.”
“How long?” asked Marissa.
“With these type of diseases, we can never be sure. Further testing will have to be done in order to come to a more valid and concrete conclusion,” said Dr. Connors.
“I don’t understand … how could this happen? A few months ago she was a healthy child and now …” gasped Marissa.
“Tay-Sachs is a mutation that causes improper activity of the enzyme Hexosaminidase. Without proper function of this enzyme, lipids build up in the brain and interfere with normal biological processes. Most children born with Tay-Sachs appear to be healthy and don’t usually show any signs until about six months of age,” described Dr. Connors.
Marissa was speechless. How could her daughter be infected with such a terrible disease? She thanked Dr. Connors for his time and headed out the door. On the way home, she couldn’t help but imagine how difficult and different life was going to be from this point forward.
“My husband and I are of Ashkenazi Jewish decent. We both grew up in a little neighborhood where the majority of the Ashkenazi Jews were located,” described Marissa.
“Are there any medical records in your family or your husband’s involving any diseases or conditions?” inquired Dr. Connors.
“Not that I can think of,” responded Marissa.
Dr. Connors nodded, placed down his ophthalmoscope and began scribbling notes in a little notebook. Marissa sat patiently, becoming anxious with every minute that passed by.
“Doctor, do you know what’s wrong with Jade?” asked Marissa.
Dr. Connors looked up at Marissa slowly and stared at her for what felt like hours. He got up, placing down his notebook and pen, and began pacing across the floor.
“Doctor, please, I’m worried. Do you know why my daughter is acting as she is?” pleaded Marissa.
Dr. Connors sighed, grabbed a seat and looked solemnly at Marissa.
“The eye examination shows that your daughter has cherry-red spots on the back of her retina. This is an indication of Tay-Sachs disease. Tay-Sachs disease is an autosomal recessive disorder that is genetically inherited. In order to have this condition, the individual must receive both copies of the recessive allele. This would mean that both you and your husband are carriers for this disease. Unfortunately, this disease is more common in the Ashkenazi population. Tay Sachs progressively destroys nerve cells in both the brain and the spinal cord. This would explain the odd symptoms that your daughter has been exhibiting recently. Sadly, there is no cure for Tay-Sachs, and it progresses to stages where the infected individual experiences seizures, vision and hearing loss, intellectual disability, paralysis and death,” explained Dr. Connors as he rubbed his eyes, “I’m very sorry.”
“How long?” asked Marissa.
“With these type of diseases, we can never be sure. Further testing will have to be done in order to come to a more valid and concrete conclusion,” said Dr. Connors.
“I don’t understand … how could this happen? A few months ago she was a healthy child and now …” gasped Marissa.
“Tay-Sachs is a mutation that causes improper activity of the enzyme Hexosaminidase. Without proper function of this enzyme, lipids build up in the brain and interfere with normal biological processes. Most children born with Tay-Sachs appear to be healthy and don’t usually show any signs until about six months of age,” described Dr. Connors.
Marissa was speechless. How could her daughter be infected with such a terrible disease? She thanked Dr. Connors for his time and headed out the door. On the way home, she couldn’t help but imagine how difficult and different life was going to be from this point forward.
Questions
1. The results of Jade’s eye examination show that she has red-cherry spots on the back of her retina. What other structure is located on the back of the retina, and which photoreceptor does it contain?
2. What is an autosomal recessive trait?
3. What is the probability that Marissa and John will have another child with Tay-Sachs disease? Include a punnett square in your answer, along with the genotypes and phenotypes of the other possible offspring.
4. Tay-Sachs progressively destroys nerve cells in the nervous system, how would the loss of nerve cells affect the muscles and movement of an individual?
5. Why wouldn’t the parents have known that their child was at risk for Tay-Sachs disease?
2. What is an autosomal recessive trait?
3. What is the probability that Marissa and John will have another child with Tay-Sachs disease? Include a punnett square in your answer, along with the genotypes and phenotypes of the other possible offspring.
4. Tay-Sachs progressively destroys nerve cells in the nervous system, how would the loss of nerve cells affect the muscles and movement of an individual?
5. Why wouldn’t the parents have known that their child was at risk for Tay-Sachs disease?
![Picture](/uploads/2/4/6/3/24638380/3780611.png?446)
Using the Pedigree provided, answer the following questions:
6. If the coloured individuals are infected with Tay Sachs disease, what are the genotypes of the following individuals?
7. If individuals III 1 and III 2 have another child, what is probability it will be a male with Tay Sachs disease?
6. If the coloured individuals are infected with Tay Sachs disease, what are the genotypes of the following individuals?
- I 2
- II 2
- II 3
- III 3
- IV 1
7. If individuals III 1 and III 2 have another child, what is probability it will be a male with Tay Sachs disease?