Question 1

Which of the following best describes heritability ($h^2$) in the context of quantitative genetics?

Accepted Answer

The proportion of total phenotypic variance that is due to additive genetic variance.

Question 2

Given the formula for heritability $h^2 = \frac{\sigma^2_A}{\sigma^2_P}$, what does $\sigma^2_A$ represent?

Accepted Answer

Additive genetic variance

Question 3

A cattle breeder is interested in improving meat tenderness. Which gene should they focus on based on QTL studies?

Accepted Answer

Calpastatin (CAST) gene

Question 4

Which of the following is a consequence of the halothane gene in pigs?

Accepted Answer

Increased susceptibility to stress and poor meat quality

Question 5

Why are most QTLs discovered using markers rather than by directly genotyping the QTL itself?

Accepted Answer

Because the actual QTL is often unknown or difficult to genotype, so markers are used as proxies.

Question 6

Which approach involves selecting a gene for physiological or biochemical reasons and identifying a polymorphism within that gene?

Accepted Answer

Candidate gene approach

Question 7

A researcher uses a high-density marker panel to scan an entire chromosome for associations with a trait. Which QTL detection approach is this?

Accepted Answer

Anonymous marker panel approach

Question 8

Which of the following best explains why quantitative traits often involve many loci?

Accepted Answer

Most traits are influenced by multiple genes, each contributing a small effect.

Question 9

If a QTL has a significant effect on a trait, what is the likely outcome in a QTL detection study?

Accepted Answer

The QTL can be detected and associated with a distinct phenotype.

Question 10

Which of the following is NOT a typical technology/method used in the candidate gene approach for QTL detection?

Accepted Answer

Genotyping individuals by high-density marker panels

Question 11

A pig breeder wants to avoid Porcine Stress Syndrome (PSS) in their herd. Which genotype should they select against?

Accepted Answer

nn or Nn at the halothane gene

Question 12

Which of the following best describes the goal of QTL detection?

Accepted Answer

To find a polymorphism in the genome associated with a distinct difference in phenotype.

Question 13

If the additive genetic variance ($\sigma^2_A$) is 40 and the total phenotypic variance ($\sigma^2_P$) is 100, what is the heritability ($h^2$)?

Accepted Answer

$h^2 = \frac{40}{100} = 0.4$

Question 14

Which of the following is a real-world application of QTL detection in livestock?

Accepted Answer

Improving meat quality by selecting for favorable alleles at the CAST gene in cattle.

Question 15

Why might a QTL with a small effect be difficult to detect in a genetic study?

Accepted Answer

Its effect on the phenotype is minor compared to environmental variation and other loci.

Question 16

Which of the following statements about the anonymous marker panel approach is TRUE?

Accepted Answer

It involves scanning a region, chromosome, or genome with multiple markers.

Question 17

A QTL is identified that increases milk yield in cattle. What is the most likely next step for a breeding program?

Accepted Answer

Select animals carrying the favorable allele to increase milk yield in future generations.

Question 18

Which of the following is a plausible reason for using marker loci (M/m) instead of directly genotyping the QTL (Q/q)?

Accepted Answer

Marker loci are often easier to genotype and may be closely linked to the QTL.

Question 19

Which of the following traits is most likely to be influenced by many loci with small effects?

Accepted Answer

Body weight in cattle

Question 20

Which technology is commonly used in the anonymous marker panel approach but not in the candidate gene approach?

Accepted Answer

Whole genome sequencing

Quantitative Trait Loci (QTL) Detection and Heritability in Plant and Animal Genetics

Study Guide - Practice Questions