S-adenosyl methionine (SAM) can function as a methyl donor for nucleotides. An i
ID: 841378 • Letter: S
Question
S-adenosyl methionine (SAM) can function as a methyl donor for nucleotides. An increase in SAM could lead to:
Transcriptional activation through methylation
Transcriptional repression through methylation
Decreased purine nucleotide synthesis
Decreased DNA histone associations
You are counseling a family with regards to maple syrup urine disease (MSUD). The couple you are speaking with currently has a child that has MSUD; neither parent is phenotypic. What is the likelihood that their next child will also have MSUD?
100%
0%
25%
50%
A mutation that inactivates the kinase domain of a protein will result in:
An increase in the phosphorylation of its target protein
A decrease in the methylation of its target protein
A decrease in the phosphorylation of its target protein
An increase in the glycosylation of its target protein
Fragile X disease is characteristic of an introduction of a large stretch of triplicate repeats upstream of the FMR1 gene. To determine the size of these large repetitive DNA regions, which technique would you use?
Southern blot
Western blot
Oligonucleotide hybridization
Northern blot
A mutation in the iron response element binding protein (IRE
Transcriptional activation through methylation
Transcriptional repression through methylation
Decreased purine nucleotide synthesis
Decreased DNA histone associations
Explanation / Answer
Maple syrup urine disease (MSUD) is caused by a gene defect. Persons with this condition cannot break down the amino acids leucine, isoleucine, and valine. This leads to a buildup of these chemicals in the blood.
In the most severe form, MSUD can damage the brain during times of physical stress (such as infection, fever, or not eating for a long time).
Some types of MSUD are mild or come and go. Even in the mildest form, repeated periods of physical stress can cause intellectual disability and high levels of leucine.
Symptoms
Exams and Tests
There will be signs of ketosis and excess acid in blood (acidosis).
Treatment
When the condition is diagnosed, and during episodes, treatment involves eating a protein-free diet. Fluids, sugars, and possibly fats are given through a vein (IV). Peritoneal dialysis or hemodialysis can be used to reduce the level of abnormal substances.
Long term treatment requires a special diet. The diet includes a man-made infant formula with low levels of the amino acids leucine, isoleucine, and valine. Persons with this condition must remain on this diet permanently.
It is very important to always follow this diet to prevent nervous system (neurological) damage. This requires frequent blood tests and close supervision by a registered dietitian and physician, as well as cooperation by the parents.
Outlook (Prognosis)
This disease can be life-threatening if untreated.
Even with dietary treatment, stressful situations and illness can still cause high levels of certain amino acids. Death may occur during these episodes. With strict dietary treatment, children have grown into adulthood and can remain healthy.
Possible Complications
When to Contact a Medical Professional
Call your health care provider if you have a family history of MSUD and are planning to start a family. Also call immediately if you have a newborn who has symptoms of maple syrup urine disease.
Prevention
Genetic counseling is suggested for people who want to have children and who have a family history of maple syrup urine disease. Many states now screen all newborns with blood tests for MSUD.
If a screening test shows that your baby may have MSUD, a follow-up blood test for amino acid levels should be done right away to confirm the disease.
Alternative Names
MSUD
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