Athena Williams was born as a healthy baby girl- and while she was small (25th percentile) the family pediatrician wasn’t worried as both her parents were petite. However at about the age of 13 months Athena stopped running around, tired easily, was pale and lost her appetite- symptoms that could not be explained by a recent flu bug going around as it lasted for months. Concerned the family pediatrician Dr. Wright decided to draw Athena’s blood to check for inherited blood-disorders. At the next office visit, Dr. Wright sat Athena’s mother down and gently gave her the bad news. As suspected it was determined that Athena had Thalassemia- an inherited disorder resulting from a defective for β-globin protein- and thus defective Hemoglobin [Like sickle cell anemia]. β-thalassemia patients are treated with frequent transfusions requiring many hospital visits, but this is not a cure. Individuals with severe forms of β-thalassemia often die in mid-teens. Dr. Wright suggested to Athena’s parents that she may be a candidate for experimental gene therapy but first they needed a quick test to see if Athena had the kind of defect that would qualify for gene therapy. They isolated mRNA from Athena’s RBCs and from a person without Thalassemia (N) and performed hybridization experiments. They allowed Athena’s mRNA to hybridize with a clone carrying the genomic DNA of b-globin gene. They did the same with mRNA from person with normal b- globin gene. Shown on the following page is the cartoon of what was observed by electron microscopy of the RNA-DNA hybrid. Double-stranded regions (hybridized) are represented by thick lines, and single-stranded regions (un-hybridized) are represented by thin lines What do the single stranded loops represent? Introns Exons 3’UTR 5’ UTR 2. How many exons and introns are there in the gene? Based on the hybridization experiments what can the pediatrician deduce about the molecular nature of the change or defect in Athena’s Beta-globin gene?
Athena Williams was born as a healthy baby girl- and while she was small (25th percentile) the family pediatrician wasn’t worried as both her parents were petite. However at about the age of 13 months Athena stopped running around, tired easily, was pale and lost her appetite- symptoms that could not be explained by a recent flu bug going around as it lasted for months. Concerned the family pediatrician Dr. Wright decided to draw Athena’s blood to check for inherited blood-disorders.
At the next office visit, Dr. Wright sat Athena’s mother down and gently gave her the bad news. As suspected it was determined that Athena had Thalassemia- an inherited disorder resulting from a defective for β-globin protein- and thus defective Hemoglobin [Like sickle cell anemia].
β-thalassemia patients are treated with frequent transfusions requiring many hospital visits, but this is not a cure. Individuals with severe forms of β-thalassemia often die in mid-teens. Dr. Wright suggested to Athena’s parents that she may be a candidate for experimental gene therapy but first they needed a quick test to see if Athena had the kind of defect that would qualify for gene therapy.
They isolated mRNA from Athena’s RBCs and from a person without Thalassemia (N) and performed hybridization experiments. They allowed Athena’s mRNA to hybridize with a clone carrying the genomic DNA of b-globin gene. They did the same with mRNA from person with normal b- globin gene.
Shown on the following page is the cartoon of what was observed by electron microscopy of the RNA-DNA hybrid.
Double-stranded regions (hybridized) are represented by thick lines, and single-stranded regions (un-hybridized) are represented by thin lines
- What do the single stranded loops represent?
- Introns
- Exons
- 3’UTR
- 5’ UTR
2. How many exons and introns are there in the gene? Based on the hybridization experiments what can the pediatrician deduce about the molecular nature of the change or defect in Athena’s Beta-globin gene?
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