CGC Cheat Sheet 2026

The 30 highest-yield CGC facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which of the following describes 'pleiotropy'? → A single gene that influences multiple phenotypic traits or organ systems
2. What term describes the phenomenon where the expression of a gene depends on whether it was inherited from the mother or the father? → Genomic imprinting
3. Which result indicates a disease-causing mutation? → Pathogenic
4. Which of the following BEST describes the purpose of a pedigree in a genetic counseling session? → To visually map family medical history and identify inheritance patterns
5. Which of the following is an example of the 'empathy' skill in genetic counseling? → Reflecting the patient's emotional state by saying 'This sounds incredibly overwhelming'
6. Which type of mutation involves the insertion of one or two nucleotides, causing a shift in the reading frame of downstream codons? → Frameshift mutation
7. The quad screen (maternal serum analytes) is a second-trimester screening test that includes which analytes? → AFP, hCG, unconjugated estriol, and inhibin A
8. A genetic counselor is writing a patient letter after a variant of uncertain significance (VUS) result. The letter should primarily: → Explain what a VUS means and emphasize the need for reclassification follow-up
9. Which pedigree symbol represents a female in genetic counseling? → Circle
10. The ACMG guideline criterion BS1 (allele frequency is greater than expected for disorder) is used as: → Strong evidence of benign classification
11. What is gene expression? → Process of making protein from a gene
12. A patient is found to have a fetus with a de novo pathogenic variant identified on exome sequencing. 'De novo' means: → The variant arose newly in the fetus and is not present in either parent
13. Why is family history still relevant with genomic testing? → It helps personalize interpretation
14. What is a potential psychosocial response to genetic testing results? → Anxiety
15. Which communication technique is most effective when disclosing a pathogenic variant result to a patient? → Deliver information in small chunks with pauses to check understanding
16. The Bethesda guidelines for colorectal cancer testing were designed to identify tumors likely to show: → Microsatellite instability (MSI)
17. The recurrence risk for a multifactorial condition in a sibling of an affected individual is BEST approximated by: → The square root of the population prevalence
18. Which PTEN-related syndrome is associated with an increased risk of breast, thyroid, endometrial, and colorectal cancers along with macrocephaly? → Cowden syndrome (PTEN hamartoma tumor syndrome)
19. Which informed consent element is MOST critical when discussing predictive genetic testing for a late-onset condition? → The potential psychological impact of knowing one's genetic status
20. Which ethical principle emphasizes doing good for the patient? → Beneficence
21. Heteroplasmy in mitochondrial genetics refers to: → A mixture of two or more mitochondrial DNA genotypes within a cell or individual
22. Which term describes the situation where a single gene mutation causes multiple, seemingly unrelated phenotypic effects? → Pleiotropy
23. The 'teach-back' method is used in genetic counseling to: → Verify that the patient has understood the information provided
24. Uniparental disomy (UPD) occurs when: → Both copies of a chromosome pair are inherited from the same parent
25. When presenting recurrence risk statistics to a patient, which format is generally MOST effective for understanding? → Natural frequencies (e.g., 1 in 4 chance)
26. A point mutation at the first position of a codon changes AUG (methionine/start) to AUG → AUA. This change would most likely result in: → Loss of the start codon, preventing normal translation initiation from that site
27. Repeat expansion testing using triplet-primed PCR or Southern blot is MOST commonly used to diagnose: → Trinucleotide repeat expansion disorders such as Huntington disease or Fragile X syndrome
28. What is the purpose of using a risk calculator in genetic counseling? → To calculate genetic risk probabilities
29. What is genetic discrimination? → Discrimination based on genetic information
30. Which counseling approach focuses on exploring and resolving ambivalence about genetic testing decisions? → Motivational interviewing