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ABGC Certification Examination (CGC) practice questions

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Question 1Genetic Counseling Practice (official content outline not enumerated in source)

A couple in which both partners are unaffected has a child with an autosomal recessive condition. Which term best describes each parent's genotype?

  1. Homozygous affected
  2. Heterozygous carrier Correct answer.
  3. Hemizygous carrier
  4. Compound heterozygote

Explanation

Unaffected parents of a child with an autosomal recessive condition each carry one pathogenic variant and one normal allele, making them heterozygous carriers. Compound heterozygosity would require two different variants within the same person, which is not established here.

Question 2Genetic Counseling Practice (official content outline not enumerated in source)

In a family with a BRCA1 pathogenic variant, which relative has the highest prior probability of also carrying the variant?

  1. A sister of the proband Correct answer.
  2. A paternal cousin of the proband
  3. A maternal aunt of the proband
  4. A spouse of the proband

Explanation

A sister shares the same parents as the proband and therefore has an a priori 50% chance of inheriting a variant present in a parent. More distant relatives have progressively lower prior probabilities depending on the intervening meioses.

Question 3Genetic Counseling Practice (official content outline not enumerated in source)

Which laboratory finding is most consistent with a diagnosis of fragile X syndrome?

  1. A point mutation in the FMR1 coding region
  2. Expansion of a CGG repeat in FMR1 Correct answer.
  3. Silencing of the FMR1 locus by uniparental disomy
  4. Deletion of the entire FMR1 promoter

Explanation

Fragile X syndrome results from expansion of a CGG trinucleotide repeat in the 5' untranslated region of FMR1 beyond the full-mutation threshold, leading to hypermethylation and gene silencing. Point mutations and deletions are rare alternative mechanisms.

Question 4Genetic Counseling Practice (official content outline not enumerated in source)

A 30-year-old woman of Ashkenazi Jewish ancestry requests preconception carrier screening. Which condition is most appropriate to include based on ancestry-based recommendations?

  1. Sickle cell disease
  2. Tay-Sachs disease Correct answer.
  3. Beta-thalassemia
  4. Cystic fibrosis

Explanation

Tay-Sachs disease has historically been associated with Ashkenazi Jewish ancestry and is a standard component of ancestry-based carrier screening panels for this population. Other conditions listed have different ancestry associations.

Question 5Genetic Counseling Practice (official content outline not enumerated in source)

A couple's first child has an autosomal recessive disorder. What is the chance that their next child is an unaffected carrier?

  1. 3 in 4
  2. 1 in 2 Correct answer.
  3. 1 in 4
  4. 2 in 3

Explanation

For two carrier parents, each pregnancy carries a 1 in 4 chance of an affected child, a 1 in 2 chance of a carrier child, and a 1 in 4 chance of a non-carrier child. The carrier probability for any pregnancy is therefore 1 in 2.

Question 6Genetic Counseling Practice (official content outline not enumerated in source)

Which feature most strongly suggests mitochondrial inheritance in a family history?

  1. Male-to-male transmission of the trait
  2. Transmission through affected females to all offspring Correct answer.
  3. Equal transmission from affected males and females
  4. Exclusive transmission to male offspring

Explanation

Mitochondrial DNA is maternally inherited, so an affected mother can pass the trait to all of her children while an affected father passes it to none. Male-to-male transmission excludes mitochondrial inheritance.

Question 7Genetic Counseling Practice (official content outline not enumerated in source)

What is the primary purpose of obtaining informed consent before genetic testing?

  1. To transfer legal ownership of the sample to the laboratory
  2. To confirm the patient has no family history of disease
  3. To guarantee that insurance will cover the test
  4. To ensure the patient understands benefits, risks, and alternatives Correct answer.

Explanation

Informed consent documents that a patient understands the purpose of testing, potential results and implications, limitations, and alternatives before proceeding. It is an educational and autonomy-protecting process, not a financial or ownership agreement.

Question 8Genetic Counseling Practice (official content outline not enumerated in source)

A variant is classified as a variant of uncertain significance. Which statement best describes the appropriate clinical use of this result?

  1. It should be treated as pathogenic for management decisions
  2. It should generally not be used to guide medical management Correct answer.
  3. It confirms the diagnosis in an affected patient
  4. It should prompt immediate predictive testing of relatives

Explanation

A variant of uncertain significance has insufficient evidence to be classified as pathogenic or benign, so it should not be used to make clinical management decisions. Reclassification may occur as evidence accumulates.

Question 9Genetic Counseling Practice (official content outline not enumerated in source)

A 45-year-old man has a strong family history of early-onset colorectal cancer but no personal history. Which testing strategy is most appropriate?

  1. Test an affected relative first, if available Correct answer.
  2. Order only tumor tissue sequencing
  3. Defer all testing until he develops symptoms
  4. Test the unaffected man with a broad panel

Explanation

When a familial pathogenic variant is suspected, testing an affected family member first is the most informative approach because it establishes whether a detectable variant segregates with disease. If a variant is found, predictive testing of unaffected relatives becomes targeted and interpretable.

Question 10Genetic Counseling Practice (official content outline not enumerated in source)

A woman is 12 weeks pregnant and has a family history of a serious autosomal recessive condition. Her partner is unavailable for testing. What is the most appropriate counseling point?

  1. The pregnancy risk is negligible without partner testing
  2. Prenatal diagnosis cannot be offered without the partner's sample
  3. Carrier testing of the woman can still inform risk Correct answer.
  4. Prenatal testing can proceed using only maternal results

Explanation

Testing the woman first is informative: if she is not a carrier of the familial variant, the risk of an affected child is very low regardless of partner status. If she is a carrier, partner testing or other strategies can then be discussed.

Question 11Genetic Counseling Practice (official content outline not enumerated in source)

Which statement about predictive testing for an adult-onset neurodegenerative condition in an asymptomatic adult is most accurate?

  1. Results may have implications for insurance and family Correct answer.
  2. Testing should be offered without psychological preparation
  3. Testing is prohibited without a court order
  4. A positive result always predicts age of onset

Explanation

Predictive testing can reveal information with psychological, insurance, and family implications, so pretest counseling addressing these issues is standard. A positive result indicates increased risk but does not determine age of onset or certainty of disease.

Question 12Genetic Counseling Practice (official content outline not enumerated in source)

A patient's newborn screening result is positive for a metabolic condition. What is the most appropriate next step?

  1. Initiate confirmatory diagnostic testing promptly Correct answer.
  2. Reassure the family that false positives are common
  3. Refer only if symptoms develop
  4. Repeat screening at age 5 years

Explanation

A positive newborn screen is a screening result, not a diagnosis, and requires prompt confirmatory testing so that treatment can begin early if the condition is confirmed. Delay risks preventable morbidity.

Question 13Genetic Counseling Practice (official content outline not enumerated in source)

A family carries a pathogenic variant in a gene associated with autosomal dominant inheritance with reduced penetrance. How should this be explained?

  1. Every carrier will develop the condition
  2. Carriers have increased risk but may remain unaffected Correct answer.
  3. Only males can be affected
  4. The variant skips generations without being transmitted

Explanation

Reduced penetrance means that not all individuals who carry a pathogenic variant express the condition, so carriers have elevated risk but may remain unaffected. The variant is still transmitted and can appear to skip generations.

Question 14Genetic Counseling Practice (official content outline not enumerated in source)

A 28-year-old woman with a BRCA1 pathogenic variant asks about risk-reducing options. Which counseling approach best supports informed decision-making?

  1. Withhold information about surgical options to reduce anxiety
  2. Advise her to decide without discussing family implications
  3. Recommend a single option as the only correct choice
  4. Present surveillance, chemoprevention, and surgery with risks and benefits Correct answer.

Explanation

Informed decision-making requires presenting the range of risk-management options with their associated benefits, limitations, and risks so the patient can choose according to her values. Directive counseling toward one option undermines autonomy.

Question 15Genetic Counseling Practice (official content outline not enumerated in source)

Which situation most clearly warrants referral for genetic counseling rather than routine primary care management alone?

  1. A 60-year-old with well-controlled hypertension
  2. A 35-year-old with a strong family history of early-onset breast cancer Correct answer.
  3. A 25-year-old with an ankle sprain
  4. A 40-year-old requesting a routine physical

Explanation

A strong family history suggesting hereditary cancer predisposition is a classic indication for genetic counseling and possible testing. Routine conditions without hereditary features are generally managed in primary care.

Question 16Genetic Counseling Practice (official content outline not enumerated in source)

A couple's child has a de novo pathogenic variant causing an autosomal dominant condition. What is the recurrence risk for future pregnancies, assuming no parental mosaicism?

  1. 25%
  2. 100%
  3. 50%
  4. 0% Correct answer.

Explanation

A true de novo variant in the child, absent parental gonadal mosaicism, implies that neither parent carries the variant, so recurrence risk is very low and approximated as near zero. Gonadal mosaicism can modestly increase this risk but is not assumed here.

Question 17Genetic Counseling Practice (official content outline not enumerated in source)

A patient with a known pathogenic variant in a cancer predisposition gene asks whether her 10-year-old child should be tested. What is the most appropriate response?

  1. Test only if the child requests it
  2. Test the child without disclosing the purpose
  3. Defer testing until the child reaches adulthood or an age of actionability Correct answer.
  4. Test the child immediately to guide surveillance

Explanation

Predictive testing for adult-onset conditions is generally deferred in minors unless there is a medical benefit during childhood. Testing is typically offered when the child reaches an age where results become actionable and can consent.

Question 18Genetic Counseling Practice (official content outline not enumerated in source)

Which factor is most important in determining whether a genetic test result is clinically actionable?

  1. The cost of the test
  2. The number of genes on the panel
  3. The availability of interventions that alter outcomes Correct answer.
  4. The patient's insurance status

Explanation

Clinical actionability depends on whether effective interventions exist that can change outcomes based on the result. Cost, panel size, and insurance status affect access but not the intrinsic actionability of a result.

Question 19Genetic Counseling Practice (official content outline not enumerated in source)

A pregnant patient's cell-free DNA screen is positive for trisomy 21. What is the most appropriate next step?

  1. Confirm with diagnostic testing such as amniocentesis or CVS Correct answer.
  2. Schedule delivery without further testing
  3. Repeat the screen in the third trimester
  4. Treat the pregnancy as diagnostic and skip confirmation

Explanation

Cell-free DNA screening is a screening test with a positive predictive value below 100%, so a positive result requires diagnostic confirmation by amniocentesis or chorionic villus sampling. Management decisions should follow diagnostic testing.

Question 20Genetic Counseling Practice (official content outline not enumerated in source)

A couple are both carriers of different pathogenic variants in the same autosomal recessive gene. What is the chance their child is affected?

  1. 25% Correct answer.
  2. 75%
  3. 0%
  4. 50%

Explanation

When each parent carries a pathogenic variant in the same gene, each child has a 1 in 4 chance of inheriting both variants and being affected, regardless of whether the variants are the same or different.

Question 21Genetic Counseling Practice (official content outline not enumerated in source)

A variant is initially classified as uncertain but later reclassified as pathogenic after segregation data emerge. What is the most important clinical implication for previously tested family members?

  1. The reclassification only matters for research
  2. Previously tested relatives may need updated interpretation and counseling Correct answer.
  3. Results should be discarded and retesting avoided
  4. No action is needed because the report was already issued

Explanation

Variant reclassification can change the clinical significance of prior results, so laboratories and clinicians should communicate updated interpretations and offer appropriate counseling and management. Family members previously tested may need revised risk information.

Question 22Genetic Counseling Practice (official content outline not enumerated in source)

A man with a pathogenic variant in an X-linked gene has a daughter. What is her carrier probability?

  1. 25%
  2. 50%
  3. 100% Correct answer.
  4. 0%

Explanation

A father transmits his X chromosome to all of his daughters, so a daughter of a man with an X-linked pathogenic variant will inherit that variant and be an obligate carrier. His sons receive his Y chromosome and are not carriers.

Question 23Genetic Counseling Practice (official content outline not enumerated in source)

A family history suggests Lynch syndrome, but tumor testing shows microsatellite stability and normal mismatch repair protein expression. How should this be interpreted?

  1. It confirms a diagnosis of Lynch syndrome
  2. It indicates the family history is irrelevant
  3. It definitively excludes Lynch syndrome in all cases
  4. It lowers but does not eliminate the possibility, so germline testing may still be considered Correct answer.

Explanation

Tumor screening results can reduce the likelihood of Lynch syndrome but do not fully exclude it, because some cases may not show mismatch repair deficiency. Germline testing may still be warranted based on family history.

Question 24Genetic Counseling Practice (official content outline not enumerated in source)

A couple presents with a child who has a clinical diagnosis consistent with an imprinting disorder. Which testing approach is most appropriate initially?

  1. Karyotype at low resolution
  2. Standard sequencing of all exons
  3. Testing only the father
  4. Methylation analysis of the relevant locus Correct answer.

Explanation

Imprinting disorders are often caused by abnormal methylation at imprinted loci, so methylation analysis of the relevant region is a first-line test. Standard sequencing and low-resolution karyotyping may miss imprinting defects.

Question 25Genetic Counseling Practice (official content outline not enumerated in source)

A patient has a pathogenic variant in a gene with variable expressivity. What does this mean for counseling?

  1. Only females will be affected
  2. Carriers may show a range of clinical features and severity Correct answer.
  3. The variant will not be transmitted
  4. All carriers will have identical symptoms

Explanation

Variable expressivity means that individuals with the same pathogenic variant can differ in the type and severity of clinical features. Counseling should convey this uncertainty rather than predict a uniform outcome.

Question 26Genetic Counseling Practice (official content outline not enumerated in source)

A genetic counselor is documenting a three-generation pedigree. Which symbol convention is standard for a person known to be an unaffected carrier of an autosomal recessive condition?

  1. A symbol with a dot in the center Correct answer.
  2. A symbol with a diagonal line through it
  3. A symbol with a vertical line through it
  4. A filled (solid) symbol

Explanation

Standard pedigree nomenclature uses a dot within an unfilled symbol to denote a confirmed carrier who is phenotypically unaffected. Filled symbols denote affected individuals, and diagonal lines denote deceased individuals.

Question 27Genetic Counseling Practice (official content outline not enumerated in source)

Which term describes the proportion of individuals with a pathogenic variant who actually manifest the associated phenotype?

  1. Expressivity
  2. Penetrance Correct answer.
  3. Heterogeneity
  4. Pleiotropy

Explanation

Penetrance is the probability that a person carrying a disease-causing genotype will express the associated phenotype. Expressivity, by contrast, refers to the range of severity among those who do express it.

Question 28Genetic Counseling Practice (official content outline not enumerated in source)

In autosomal recessive inheritance, what is the recurrence risk for each subsequent child of two confirmed carriers?

  1. 50%
  2. 0%
  3. 25% Correct answer.
  4. 75%

Explanation

Two carriers each contribute one pathogenic allele with probability one-half, so the chance that a child inherits both is 1/2 × 1/2 = 25%. This risk applies independently to each pregnancy.

Question 29Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is preparing a session for a patient with limited health literacy. Which communication strategy best supports patient understanding?

  1. Providing written materials only and deferring questions
  2. Using plain language and checking understanding with teach-back Correct answer.
  3. Using full technical terminology so the record is precise
  4. Avoiding any discussion of uncertainty

Explanation

Plain-language communication combined with teach-back confirms that the patient can restate key information in their own words. This approach is a core genetic counseling skill for supporting informed decision-making.

Question 30Genetic Counseling Practice (official content outline not enumerated in source)

Which concept refers to the counselor's obligation to act in the patient's best interest while respecting the patient's own values and choices?

  1. Veracity
  2. Justice
  3. Confidentiality
  4. Beneficence Correct answer.

Explanation

Beneficence is the ethical principle of promoting the patient's welfare, balanced in genetic counseling with respect for autonomy. Veracity concerns truthfulness, justice concerns fairness, and confidentiality concerns protecting private information.

Question 31Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is explaining an X-linked recessive condition. Which statement about transmission is accurate?

  1. Affected fathers pass the condition to all of their sons
  2. Carrier mothers pass the variant to half of their offspring on average Correct answer.
  3. Only males can carry the pathogenic variant
  4. Female carriers are always unaffected

Explanation

A female carrier has one pathogenic and one normal X chromosome, so each child has a 50% chance of inheriting the pathogenic allele regardless of sex. Affected fathers transmit their Y chromosome to sons, so sons are not affected through that route.

Question 32Genetic Counseling Practice (official content outline not enumerated in source)

Which document specifically records a patient's preferences about future use of stored genetic material and disclosure of results?

  1. A pedigree chart
  2. A letter of medical necessity
  3. An informed consent form for biobanking Correct answer.
  4. A laboratory requisition form

Explanation

Consent forms for biobanking address storage, future research use, and disclosure preferences for stored samples and data. Pedigrees and requisitions serve documentation and ordering functions rather than consent.

Question 33Genetic Counseling Practice (official content outline not enumerated in source)

What is the primary purpose of a genetic counseling session that follows disclosure of a pathogenic variant result?

  1. To help the patient understand implications and make informed decisions Correct answer.
  2. To persuade the patient to pursue a specific medical intervention
  3. To collect billing information for the laboratory
  4. To confirm the laboratory's analytic validity

Explanation

Post-test counseling focuses on helping patients understand the result's implications for themselves and relatives and on supporting informed, value-consistent decisions. The counselor's role is non-directive rather than persuasive.

Question 34Genetic Counseling Practice (official content outline not enumerated in source)

A 34-year-old woman of Ashkenazi Jewish ancestry with no personal or family history of cancer asks about carrier screening. Which statement best reflects current practice?

  1. Screening is not offered without a family history
  2. Screening should be deferred until she has an affected child
  3. Screening may be offered because ancestry increases carrier frequency for several conditions Correct answer.
  4. Screening is limited to diagnostic testing after symptoms appear

Explanation

Certain ancestries are associated with higher carrier frequencies for specific autosomal recessive conditions, supporting the offer of carrier screening regardless of family history. Screening is elective and based on informed choice.

Question 35Genetic Counseling Practice (official content outline not enumerated in source)

A counselor notes that a patient's sibling shares a pathogenic variant but has a milder phenotype than the patient. Which explanation is most consistent with this observation?

  1. Variable expressivity of the same variant Correct answer.
  2. A laboratory sample swap in both siblings
  3. Non-paternity in the family
  4. The variant must have been misclassified

Explanation

The same pathogenic variant can produce a range of phenotypic severity, a phenomenon termed variable expressivity. This does not by itself indicate a classification error or sample problem.

Question 36Genetic Counseling Practice (official content outline not enumerated in source)

A couple's first child has an autosomal dominant condition caused by a de novo pathogenic variant. What is the most appropriate estimate of recurrence risk for future pregnancies?

  1. 50%, because one parent must be affected
  2. 25%, as in autosomal recessive inheritance
  3. About 1%, accounting for possible gonadal mosaicism Correct answer.
  4. Essentially zero, because the variant is de novo

Explanation

De novo variants carry a small recurrence risk, typically estimated at around 1%, because of the possibility of gonadal mosaicism in a parent. This risk is much lower than the 50% seen with an inherited dominant variant.

Question 37Genetic Counseling Practice (official content outline not enumerated in source)

A patient with a strong family history of a hereditary cancer syndrome is considering testing. Which factor is most relevant to determining whether testing a specific relative first is useful?

  1. The patient's preferred testing laboratory
  2. The patient's insurance deductible
  3. Whether an affected relative with a known pathogenic variant is available for testing Correct answer.
  4. The number of siblings the patient has

Explanation

Testing an affected relative first can establish the familial pathogenic variant, allowing predictive testing of at-risk relatives. If no affected relative carries a variant, testing unaffected relatives has limited interpretive value.

Question 38Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is discussing a variant of uncertain significance in a cancer predisposition gene. Which counseling point is most appropriate?

  1. Tell the patient the variant is definitely benign
  2. Recommend risk-reducing surgery based on the variant
  3. Advise that relatives do not need to be informed
  4. Explain that the result should not be used to guide management without further evidence Correct answer.

Explanation

A variant of uncertain significance lacks sufficient evidence to guide clinical management and should not be treated as pathogenic. Management should follow family history and other clinical factors.

Question 39Genetic Counseling Practice (official content outline not enumerated in source)

Which principle best justifies a counselor's decision to disclose a patient's genetic result to an at-risk relative without the patient's consent in a narrowly defined circumstance?

  1. Autonomy
  2. Confidentiality
  3. Veracity
  4. Duty to warn Correct answer.

Explanation

The duty to warn may, in limited circumstances, justify disclosure to an at-risk relative when serious harm is preventable and the patient refuses to inform them. Confidentiality generally prevails, and disclosure is considered only under narrow conditions.

Question 40Genetic Counseling Practice (official content outline not enumerated in source)

A patient asks whether a direct-to-consumer genetic test can replace clinical diagnostic testing. Which response is most accurate?

  1. Consumer tests are prohibited for any health-related purpose
  2. Consumer tests are always more accurate than clinical tests
  3. Consumer tests may have different analytic standards and should be confirmed clinically Correct answer.
  4. Consumer tests are equivalent to clinical testing in all respects

Explanation

Direct-to-consumer tests vary in analytic and clinical validity and generally should not replace clinical-grade testing. Clinically significant results should be confirmed in an accredited laboratory.

Question 41Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is reviewing a family in which a condition appears in every generation and affects both males and females, with male-to-male transmission observed. Which inheritance pattern is most consistent?

  1. Mitochondrial
  2. Autosomal dominant Correct answer.
  3. X-linked recessive
  4. Autosomal recessive

Explanation

Male-to-male transmission excludes X-linked inheritance, and appearance in every generation with both sexes affected is characteristic of autosomal dominant inheritance. Mitochondrial inheritance is transmitted through mothers, and recessive conditions often skip generations.

Question 42Genetic Counseling Practice (official content outline not enumerated in source)

A patient with a known pathogenic variant in a highly penetrant gene asks about informing her adult siblings. What is the most appropriate counseling approach?

  1. Advise the patient that siblings cannot be at risk
  2. Provide a family letter and support the patient's decision to share information Correct answer.
  3. Refuse to discuss relatives because of confidentiality
  4. Contact the siblings directly without the patient's knowledge

Explanation

Counselors commonly provide a family communication letter and support the patient's autonomous decision about sharing results. Direct contact without consent is generally inappropriate except in narrowly defined duty-to-warn situations.

Question 43Genetic Counseling Practice (official content outline not enumerated in source)

Which test is most appropriate for detecting a large deletion or duplication that might be missed by sequencing alone?

  1. Karyotype at low resolution
  2. Sanger sequencing of a single exon
  3. Chromosomal microarray or deletion/duplication analysis Correct answer.
  4. Methylation-specific PCR

Explanation

Chromosomal microarray and deletion/duplication analysis detect copy-number changes that standard sequencing may not identify. Low-resolution karyotype may miss small deletions, and methylation testing addresses imprinting.

Question 44Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is explaining the difference between analytic validity and clinical validity. Which statement best describes clinical validity?

  1. How much the test costs
  2. How reliably a test detects a specific variant in the laboratory
  3. How the result improves patient outcomes
  4. How consistently a test result predicts the presence or risk of a condition Correct answer.

Explanation

Clinical validity describes how well a test result correlates with the presence or risk of a condition. Analytic validity concerns laboratory detection, and clinical utility concerns improvement in outcomes.

Question 45Genetic Counseling Practice (official content outline not enumerated in source)

A family has a child with an autosomal recessive condition, and both parents are confirmed carriers. What is the chance that a future unaffected child is a carrier?

  1. One-half
  2. Three-quarters
  3. Two-thirds Correct answer.
  4. One-quarter

Explanation

Among unaffected children of two carriers, the possible genotypes are one homozygous normal and two carrier genotypes, giving a carrier probability of 2/3. The 1/4, 1/2, and 3/4 figures apply to the unconditional risks for all offspring.

Question 46Genetic Counseling Practice (official content outline not enumerated in source)

A counselor learns that a pathogenic variant was reclassified as benign after a patient already made a decision based on the earlier result. What is the most appropriate action?

  1. Remove the result from the medical record
  2. Wait until the patient's next routine visit in several years
  3. Contact the patient to discuss the reclassification and its implications Correct answer.
  4. Take no action because the patient already decided

Explanation

When a variant is reclassified, the counselor has a responsibility to inform the patient and discuss how the new interpretation affects prior decisions. Prompt communication supports informed management.

Question 47Genetic Counseling Practice (official content outline not enumerated in source)

A couple in which the mother carries an X-linked recessive pathogenic variant has a daughter with mild features of the condition. Which explanation is most plausible?

  1. The daughter has skewed X-inactivation favoring the pathogenic allele Correct answer.
  2. The variant must be autosomal dominant
  3. The daughter inherited the variant from her father
  4. The daughter cannot carry the variant because she is female

Explanation

Skewed X-inactivation can cause female carriers of X-linked recessive variants to manifest mild features. Fathers transmit their X chromosome only to daughters but would not transmit an X-linked recessive variant from the mother's side in this scenario.

Question 48Genetic Counseling Practice (official content outline not enumerated in source)

A patient's genetic test reports a variant of uncertain significance in a gene where the family history is strongly suggestive of disease. Which next step is most appropriate?

  1. Recommend testing only the patient's children
  2. Pursue segregation or functional evidence and consider research or additional testing Correct answer.
  3. Disregard the family history entirely
  4. Treat the variant as pathogenic because of the family history

Explanation

Additional evidence such as segregation, functional studies, or reanalysis can help reclassify a variant of uncertain significance. Family history remains relevant and should not be disregarded.

Question 49Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is asked to explain why a condition caused by a triplet repeat expansion may show anticipation. Which explanation is most accurate?

  1. The repeat length can increase in successive generations, often worsening severity Correct answer.
  2. The condition becomes less severe with each generation
  3. The variant is inherited only from fathers
  4. The variant is lost in later generations

Explanation

Anticipation occurs when a repeat expansion increases in size across generations, often leading to earlier onset or greater severity. The expansion can be transmitted through either parent, though some disorders show parent-of-origin effects.

Question 50Genetic Counseling Practice (official content outline not enumerated in source)

A counselor is evaluating whether to recommend a prenatal diagnostic test after a prior child with a known pathogenic variant. Which factor is most relevant to the recommendation?

  1. The number of prior pregnancies
  2. The counselor's personal views on testing
  3. The parents' reproductive goals and preferences Correct answer.
  4. The laboratory's turnaround time alone

Explanation

The decision to pursue prenatal diagnosis should be guided by the parents' informed reproductive goals and preferences. The counselor's role is to provide information and support rather than to direct the choice.