Quantitative Genetics Practice Test
Review the following concepts if needed:
- Qualitative vs. Quantitative Traits for Genetics
- Polygenic Traits for Genetics
- The Normal Distribution for Genetics
- Types of Gene Action for Genetics
- Heritability for Genetics
- Selection Methods for Genetics
- Mating Methods for Genetics
Vocabulary For each of the following definitions, give the appropriate term and spell it correctly. Terms are single words unless indicated otherwise.
- The kind of phenotypic variation associated with quantitative traits. (One or two words.)
- A bell-shaped distribution of continuous phenotypic variation. (One or two words.)
- A squared standard deviation.
- A type of allelic interaction in which the phenotype of a heterozygote is outside the phenotypic limits of the corresponding homozygotes.
- The proportion of the phenotypic variance of a trait that is attributable to gene effects.
- A statistic expressing how much (on average) one sample variable may be expected to change per unit change in some other variable. (Two words.)
- A statistical measurement of how closely two sets of sample data are associated, having limits ±1. (Two words.)
- A method of estimating the breeding value of an individual by the performance or phenotype of its offspring. (Two words.)
- The mating of individuals that are more closely related than the average of the population to which they belong.
- The superior phenotypic quality of heterozygotes relative to that of homozygotes, commonly called "hybrid vigor."
Multiple-Choice Questions Choose the one best answer.
For problems 1–3, use the following information. Two pure lines of corn have mean cob lengths of 9 and 3 in, respectively. The polygenes involved in this trait all exhibit additive gene action.
- Crossing these two lines is expected to produce a progeny with mean cob length (in inches) of (a) 12.0 (b) 7.5 (c) 6.0 (d) 2.75 (e) none of the above
- If the variation in F1 cob length ranges from 5.5 to 6.5 in, this variation is estimated to be due to segregation at (a) two loci (b) three loci (c) four loci (d) five loci (e) none of the above
- If only two segregating loci contribute to cob length, and we represent the parental cross as AABB (9-in average cob length) × aabb(3-in average), the fraction of the F2 expected to be 4.5 in is (a) 1/8 (b) 1/16 (c) 3/32 (d) 3/16 (e) none of the above
- If a mouse population has an average adult body weight of 25 g with a standard deviation of ±3 g, the percentage of the population expected to weigh less than 22 g is approximately (a) 16 (b) 33 (c) 68 (d) 50 (e) 25
- With reference to problem 4 above, if the genetic variance in mouse body weight is 2.7, the environmental variance is approximately (a) 22.3 (b) 6.3 (c) 0.3 (d) 3.3 (e) none of the above
- In another population of mice, the total genetic variance of adult bodyweight is 4g2 and the environmental variance is 12g2. The broad estimate of heritability for this trait in this population is approximately (a) 0.15 (b) 0.20 (c) 0.25 (d) 0.33 (e) none of the above
- If the correlation coefficient between body weight of full sibs is 0.15, then the heritability of this trait in this population is (a) less than 0.15 (b) 0.25 (c) 0.3 (d) 0.6 (e) none of the above
- The selection differential (in grams) is (a) 0.5 (b) 4 (c) 3.5 (d) 2 (e) none of the above
- The genetic gain (in grams) is (a) 0.5 (b) 4 (c) 3.5 (d) 2 (e) none of the above
- The heritability estimate for adult body weight in this population is (a) 0.050 (b) 0.625 (c) 0.125 (d) 0.250 (e) none of the above
For problems 8-10, use the following information. A population of adult mice has a mean body weight of 30 g. The average weight of mice selected for breeding purposes is 34g. The progeny produced by random mating among the selected parents average 30.5g.
- continuous variation
- normal (or Gaussian) distribution
- heritability (broad definition)
- regression coefficient
- correlation coefficient
- progeny test
- e (environmental)
- e (1/4)
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