CDN Nutritional Genomics & Precision 4 — Questions and Answers
Question 1: A client with homozygous MTHFR C677T variant is best supported by which form of folate supplementation?
- Folic acid (synthetic form)
- 5-methyltetrahydrofolate (5-MTHF) (Correct answer)
- Folinic acid only
- No supplementation is needed
Correct answer: 5-methyltetrahydrofolate (5-MTHF)
5-MTHF bypasses the impaired MTHFR enzyme and is directly usable for methylation reactions, unlike synthetic folic acid which requires conversion.
Question 2: Which gene variant is most clinically relevant when counseling a patient about vitamin D supplementation requirements?
- CYP1A2
- VDR Fok1 polymorphism (Correct answer)
- COMT Val158Met
- SLC30A8
Correct answer: VDR Fok1 polymorphism
VDR Fok1 (rs2228570) alters vitamin D receptor protein length and transcriptional activity, influencing individual responsiveness to vitamin D supplementation.
Question 3: The HFE gene C282Y homozygous variant is most associated with which nutritional disorder?
- Zinc deficiency
- Hereditary hemochromatosis with iron overload (Correct answer)
- Magnesium malabsorption
- Copper deficiency
Correct answer: Hereditary hemochromatosis with iron overload
HFE C282Y homozygosity is the most common cause of hereditary hemochromatosis, leading to excessive intestinal iron absorption and organ iron deposition.
Question 4: In the context of nutrigenomics, 'gene expression profiling' using microarrays measures:
- DNA sequence variants across the genome
- mRNA levels of thousands of genes simultaneously (Correct answer)
- Protein folding patterns in response to nutrients
- Epigenetic methylation at individual CpG sites
Correct answer: mRNA levels of thousands of genes simultaneously
Microarray technology hybridizes labeled cDNA to probe arrays to quantify the transcriptomic response to dietary interventions across thousands of genes.
Question 5: A client with the COMT Val158Met low-activity genotype (Met/Met) may have altered metabolism of which dietary compound?
- Saturated fatty acids
- Catechol-containing polyphenols such as quercetin and EGCG (Correct answer)
- Sucrose and fructose
- Dietary cholesterol
Correct answer: Catechol-containing polyphenols such as quercetin and EGCG
COMT methylates and inactivates catechol-structured compounds; the Met/Met variant reduces this activity, prolonging the effects of catechol polyphenols and catecholamines.
Question 6: Genome-wide association studies (GWAS) in nutrition research are primarily limited by:
- Inability to detect any variants with small effect sizes
- Difficulty translating statistical associations to functional dietary recommendations (Correct answer)
- Measuring only mitochondrial DNA variants
- Excluding all non-European populations by design
Correct answer: Difficulty translating statistical associations to functional dietary recommendations
Most GWAS-identified variants have small effect sizes and unknown functional mechanisms, making translation into actionable clinical nutrition guidance challenging.
Question 7: The omega-3 index reflects the percentage of EPA and DHA in red blood cell membranes and is considered optimal when:
- Above 8% (Correct answer)
- Between 2-4%
- Below 2%
- Exactly 6%
Correct answer: Above 8%
An omega-3 index above 8% is associated with the lowest cardiovascular risk, while values below 4% indicate high risk.
CDN Nutritional Genomics & Precision 4
A client with homozygous MTHFR C677T variant is best supported by which form of folate supplementation?