How Rare Am I Genetically Quiz
Questions: 16 · 10 minutes
1. You learn that you have three individually uncommon traits. What else is needed before estimating how uncommon their combination is?
Only the frequency of the rarest trait
Confirmation that all three traits are visible
Proof that each trait is controlled by a single gene
Relevant frequencies, a defined reference population, and information about whether the traits are statistically dependent
2. Which statement best reflects how a typical polygenic trait, such as height, is influenced?
The trait’s frequency directly reveals the frequency of every contributing variant.
One rare variant usually determines the entire trait in everyone.
Only variants inherited from the mother affect the trait.
Many genetic variants can contribute, often alongside environmental influences.
3. Two uncommon variants lie close together on one chromosome and are often inherited as a pair. What mistake could result from multiplying their separate frequencies as if they were independent?
It could make the paired combination appear rarer than it actually is.
The calculation would prove that both variants cause the same trait.
It would convert their allele frequencies into penetrance estimates.
It would show that the variants must have arisen in the same person.
4. For a two-allele locus with allele frequencies p and q, which expression gives the expected heterozygote frequency under Hardy-Weinberg assumptions?
2pq
p²
q²
p + q
5. When is it generally valid to estimate the frequency of a combination by multiplying the individual feature frequencies?
Whenever all the features are visible traits
When the features are independent, or dependence has been properly accounted for
Whenever the features come from the same chromosome
Whenever each feature is found in fewer than 10% of people
6. A genetic database contains very few participants from a person’s ancestry group. How should a reported rarity estimate for that person be treated?
As more accurate, because smaller reference groups contain less variation
As universal, because ancestry does not affect allele-frequency estimates
With caution, because underrepresentation can make variants look rarer or less well characterized
As evidence that the person has more mutations than average
7. A report says someone has several rare variants. What additional information is most necessary for interpreting that claim?
Whether the person has any visibly unusual traits
Whether all the variants occur on the longest chromosome
The person’s total number of chromosomes
The comparison population, frequency thresholds, and variants examined
8. A variant occurs in 0.5% of Population X but 8% of Population Y. Which description is most accurate?
Its rarity depends on which population is being used as the reference.
The variant is objectively rare because its lowest measured frequency is below 1%.
The difference proves that one population was tested incorrectly.
The variant must produce different traits in the two populations.
9. A genotype occurs in about 1 out of every 10,000 people in a representative population. Roughly how many carriers would be expected among 1,000,000 people, assuming random sampling?
10
50
1,000
100
10. What is a de novo genetic variant?
A variant that arose in an egg, sperm, or early embryo rather than being inherited from either parent
A common ancestral variant newly added to a reference database
A variant inherited from both parents at the same time
A DNA difference caused only by changes in diet or exercise
11. In a large randomly mating population, allele A has frequency 1% and allele a has frequency 99%. Under Hardy-Weinberg assumptions, approximately what percentage is expected to have genotype Aa?
0.01%
About 2%
1%
About 99%
12. Why can the same genetic variant be described as rare in one study but not in another?
A variant becomes rarer whenever a larger DNA segment is tested.
Rarity is measured relative to a reference population and a stated frequency threshold.
Only variants that alter visible traits can have measurable frequencies.
Every laboratory uses a different genetic code for the same population.
13. A recessive genetic condition is much less common than the allele associated with it. What is the best explanation?
Recessive alleles disappear whenever they are inherited from only one parent.
The condition may require two relevant copies, while people with one copy can be unaffected carriers.
Only visible genetic traits can be counted reliably in a population.
People with one copy cannot pass the allele to their children.
14. What best explains why an individual’s full inherited combination of DNA is typically highly distinctive?
Common genetic variants are removed before birth.
Every person receives entirely new chromosomes not found in either parent.
Meiosis reshuffles parental DNA, and inherited variants occur in an enormous number of possible combinations.
Each person uses a slightly different genetic code to produce proteins.
15. Two people share an uncommon eye-color pattern. What can you reasonably conclude from that observation alone?
They must carry exactly the same variants affecting eye color.
They are likely to be close biological relatives.
The appearance alone is insufficient to calculate either person’s overall genetic rarity.
Their complete genomes are rarer than those of people with common eye colors.
16. Among 100 people carrying a particular genotype, 60 show the associated trait. What is the observed penetrance in this group?
40%
100%
60%
It cannot be estimated unless the genotype is rare.