Which genetic-based disorders can be initially identified by the most common types of newborn blood screening? Select all that apply.
A patient is 34 years old and concerned about possibly being a carrier for HNPCC because his father died of colon cancer at 39, his father’s sister died of colon cancer at age 41, and his brother (aged 37) now has colon cancer. The brother’s testing is negative for all the known mutations associated with inherited forms of colon cancer. How should this patient be counseled about his risk for colon cancer?
A)Explain that because the brother with cancer is negative for these gene mutations, this cancer is most likely sporadic, and his risk is the same as that for the general population.
B)Explain that he could benefit from testing even though his brother is negative for these mutations because reduced penetrance might account for his negative status.
C)Explain that testing for him would be of no benefit because of the current test limitations but that his family history does place him at high risk.
D)Explain that his risk is not related to his brother’s diagnosis because he did not inherit any genes from him, but because his father is a first-degree relative, testing should be considered.
A woman whose sister tested positive for a specific mutation in the BRCA1 gene, which increases the risk for breast and ovarian cancer, is found not to have that mutation but does have a mutation of unknown significance near the known mutation site. How should this woman be counseled?
A)She should be informed that her risk for breast cancer is greater than that of the general population but not as great as her sister’s risk.
B)She should be informed that because she does not have the mutation, her risk for breast cancer is not greater than that of the general population.
C)She should be informed that she does not have the specific mutation but that because another mutation is present, she should be vigilant about screening.
D)She should be informed of her gene-mutation status and be presented with all the available prophylaxis options and reconstruction options.
When is fluorescence in situ hybridization (FISH) most likely to be used?
A)To find a gene associated with a particular disease
B)To determine whether a stillborn infant has trisomy 13
C)To determine the carrier status of a child whose sister has cystic fibrosis
D)To establish a diagnosis for a possible adult-onset single-gene disorder
What is the major disadvantage to the fluorescence in situ hybridization (FISH) method of genetic testing?
A)Single-nucleotide mutations cannot be detected.
B)Depending on the skill of the technician, the rate of false positives is high.
C)The sample for testing must be obtained from living tissue rather than from a preserved specimen.
D)Results are not available quickly because cells must first be grown in culture before testing can be performed.
How is the polymerase chain reaction (PCR) helpful in the process of genetic testing?
A)Preserving genetic material within a sample so that more sophisticated tests can be performed as they become available with future technologic advancements
B)Separating exons from introns and establishing which DNA strand is the “sense” strand
C)Determining whether a small amount of DNA is paternal or maternal in origin
D)Increasing the amount of DNA being tested, thus promoting accuracy
Which type of genetic testing examines a person’s chromosomes for variations in number or structure?
Which type of genetic testing is the most sensitive method for detecting any mutation in a specific gene?
B)Direct DNA sequencing
C)Banded chromosomal analysis
D)Fluorescence in situ hybridization
Genetic testing of an asymptomatic woman whose sister is positive for the mutation that is responsible for an autosomal-dominant disorder that has a 70% penetrance ratewould fall into which testing category?
Under which condition can preimplantation genetic testing be performed?
A)During in vitro fertilization
B)Between 4 to 6 weeks’ gestation
C)When paternity is unknown
D)When an ultrasound indicates the fetus has a structural abnormality