In the context of estimating and interpreting the recurrence risks for genetic disorders, which statement should nurses be aware of?
The risk factor remains constant regardless of the number of affected children in the family.
An autosomal recessive disease carries a one in eight risk of the second child also having the disorder.
Disorders involving maternal ingestion of drugs carry a one in four chance of being repeated in the second child.
With a dominant disorder, the likelihood of the second child also having the condition is 100%.
The Correct Answer is B
Choice A rationale:
This statement is incorrect. The risk factor for a genetic disorder can vary depending on the specific disorder and the family history. For example, the risk of having a child with an autosomal recessive disorder is higher if there is a history of the disorder in the family.
Additionally, some genetic disorders have a higher risk of recurrence than others. For example, the risk of having a child with cystic fibrosis is 25% if both parents are carriers of the gene.
It's crucial for nurses to be aware of the varying risk factors associated with different genetic disorders to provide accurate information and counseling to families.
Choice C rationale:
This statement is also incorrect. The risk of a disorder involving maternal ingestion of drugs being repeated in the second child depends on several factors, including the specific drug, the dose, and the timing of exposure.
It cannot be generalized to a one in four chance for all drug-related disorders. Nurses should consult with appropriate resources and specialists to determine the specific risks associated with different drugs and exposures.
Choice D rationale:
This statement is incorrect for autosomal dominant disorders. With an autosomal dominant disorder, the likelihood of the second child also having the condition is 50%, not 100%. Each child has a 50% chance of inheriting the affected gene from the affected parent.
It's essential for nurses to understand the inheritance patterns of different genetic disorders to provide accurate information and support to families.
Choice B rationale:
This statement is correct. An autosomal recessive disease carries a one in eight risk of the second child also having the disorder. This is because both parents must be carriers of the affected gene for a child to inherit the disorder.
If both parents are carriers, there is a 25% chance that each child will inherit two copies of the affected gene and have the disorder. However, there is also a 50% chance that each child will inherit only one copy of the affected gene and be a carrier, and a 25% chance that each child will inherit two normal copies of the gene and not be affected.
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Correct Answer is C
Explanation
The correct answer is C. Only one copy of the variant gene is needed for expression of the disease.
Choice A rationale:
Huntington's disease (HD) is not typically diagnosed in childhood. While symptoms can sometimes manifest in adolescence or early adulthood, the average age of onset is between 30 and 50 years old.
Early-onset HD, which occurs before the age of 20, is much rarer and accounts for only about 5-10% of cases.
It's crucial to convey accurate information about the typical age of onset to avoid unnecessary anxiety and unwarranted testing in children.
Choice B rationale:
The statement "If you are a carrier, there is a 25% chance your child will inherit the gene" is not entirely accurate for autosomal dominant disorders like HD.
If a parent has HD, each child has a 50% chance of inheriting the mutated gene, not 25%. This is because the parent with HD has one mutated copy of the gene and one normal copy.
During conception, each child randomly receives one copy of the gene from each parent. Therefore, there's a 50% chance the child will receive the mutated copy and a 50% chance they'll receive the normal copy.
Choice D rationale:
Referral to a genetic counselor is essential for all individuals with a family history of HD, regardless of their carrier status.
Genetic counselors can provide comprehensive information about HD, including: Inheritance patterns
Risk assessment
Testing options
Reproductive options
Support resources
Psychosocial counseling
They can assist individuals in making informed decisions about testing, family planning, and management of the condition.
Choice C is the correct answer because:
HD is indeed an autosomal dominant disorder, meaning that only one copy of the mutated gene is needed for an individual to develop the disease.
This contrasts with autosomal recessive disorders, which require two copies of the mutated gene (one from each parent) for the disease to manifest.
Understanding the pattern of inheritance is crucial for accurate risk assessment and genetic counseling.
Correct Answer is D
Explanation
Choice A rationale:
Fetal lung maturity is not assessed through chorionic villus sampling (CVS). It's primarily evaluated through amniocentesis, a different prenatal diagnostic procedure that involves sampling amniotic fluid.
CVS focuses on placental tissue, not lung development.
It's essential for clients to understand the specific purposes of each prenatal test to make informed decisions and have accurate expectations.
Choice B rationale:
While a non-stress test (NST) might be recommended after CVS in some cases, it's not a routine part of the procedure.
The decision to conduct an NST is based on individual risk factors and assessment by healthcare providers.
It's essential for clients to understand the potential need for additional testing but not assume it's always required.
Choice C rationale:
CVS is considered an invasive procedure, as it involves entering the uterus to collect placental tissue.
Non-invasive prenatal testing (NIPT) methods, which analyze fetal DNA in maternal blood, are available for screening purposes.
It's crucial for clients to differentiate between invasive and non-invasive prenatal testing options to make informed choices based on their preferences and risk factors.
Choice D rationale:
This statement accurately reflects the primary purpose of CVS.
It's a diagnostic procedure that can detect various genetic abnormalities, such as Down syndrome, cystic fibrosis, and TaySachs disease, during the first trimester of pregnancy.
Understanding the ability to detect genetic abnormalities early in pregnancy allows clients to make informed decisions about their pregnancy management and prepare for potential outcomes.
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