CGC Study Guide 2026
Everything you need to pass the CGC exam in one place: the exam format, every topic to study, real practice questions with explanations, flashcards, and full-length practice tests. Free, no sign-up needed.
📋 CGC Exam Format at a Glance
📚 CGC Topics to Study (22)
✍️ Sample CGC Questions & Answers
1. Which of the following describes a mutation?
A mutation is defined as a change in the DNA sequence of an organism. These changes can range from a single nucleotide alteration to large-scale chromosomal rearrangements. Mutations can occur spontaneously or be induced by external factors, and they are the ultimate source of genetic variation, sometimes leading to disease or providing evolutionary advantage.
2. A patient asks about the difference between a 'screen positive' and a 'diagnostic positive' result for Down syndrome. The counselor correctly explains that:
Screening identifies individuals at increased risk who need diagnostic testing, while diagnostic testing provides definitive chromosomal confirmation.
3. Which condition is typically associated with autosomal recessive inheritance?
Cystic fibrosis is a classic example of an autosomal recessive condition.
4. Which law protects individuals from genetic discrimination in the U.S.?
The Genetic Information Nondiscrimination Act (GINA) prohibits misuse of genetic information.
5. What does autosomal dominant inheritance imply?
A single copy of the mutated gene from either parent can cause the disorder.
6. Which of the following epigenetic modifications most directly contributes to gene silencing by adding a chemical group to cytosine residues in CpG islands?
DNA methylation at CpG islands, catalyzed by DNA methyltransferases, is strongly associated with transcriptional silencing of the associated gene.