Concept explainers
(a)
To determine: The narrow-sense heritability (h2) for each trait in the given problem.
Introduction: The contribution of genotypic variance concerning the total
(b)
To determine: The trait that will respond likely to selection.
Introduction: The term heritability explains the ratio of the total phenotypic variation due to genetic components in a population. The values of heritability are used in animal and plant breeding to point the potential response of a population to artificial selection for a quantitative trait.
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EBK CONCEPTS OF GENETICS
- 1) Narrow sense heritability of withers height in a population of quarter horses is 17%. The average withers height in this population is 17.5 hands (1 hand is equal to 4 inches). From this population, studs and mares with average withers height of 19.8 hands are selected as parents for the next generation. 1a) Calculate the selection differential and expected response to selection for withers height in this population. 1b) What should be the average withers height in the progeny of the selected animals?arrow_forwardThe following table shows the number of dogs for certain tail lengths in a population of dogs. Tail Length Number of Dogs very short (less than 1 inch) 2 short (1–5 inches) 5 medium (5–10 inches) 15 long (10–15 inches) 5 very long (15–25 inches) 2 Based on this data, what type of trait is tail length in dogs? (a) Mendelian (b) codominant (c) (d) polygenicarrow_forwardA hypothetical study investigated the vitamin A content and thecholesterol content of eggs from a large population of chickens.The variances (V) were calculated, as shown at the top of the nextcolumn: Variance Vitamin A CholesterolVP 123.5 862.0VE 96.2 484.6VA 12.0 192.1VD 15.3 185.3 Calculate the narrow-sense heritability (h2) for bothtraits.arrow_forward
- In a population of locusts, the mean wing length is 47 mm, the selection gradient on wing length is β = 0.12/mm, the phenotypic variance for wing length is P = 3.6 mm2, and the heritability of wing length is h2 = 0.27. In addition, we know that the additive genetic covariance between wing and leg length is 0.60 mm2. What is the expected evolutionary change in mean leg length due to selection on both wings and legs? Repeat these calculations to predict what will happen to wing length as a result of the selection on both wings and legs. What do you predict the average wing and leg lengths will be in the next generation?arrow_forwardEach graph below depicts reaction norms for three different genotypes reared in different environments. In which case(s) is/are VE> 0 (you can assume that graphs for parents and their offspring would be the same)? Mark all that apply Mean phenotype (a) (c) graph a graph b graph c graph d (b) (d) Environmentarrow_forwardMany researchers have estimated the heritability of human traits by comparing the correlation coefficients of monozygotic and dizygotic twins (see pp. 731–732). One of the assumptions made in using this method is that monozygotic twin pairs experience environments that are no more similar to each other than those experienced by dizygotic twin pairs. How might this assumption be violated? Give some specific examples of how the environments of two monozygotic twins might be more similar than the environments of two dizygotic twins.arrow_forward
- Example 3.5.7 Fish Vertebrae Consider the distribution of vertebrae given in Table 3.5.1. In Exam- ple 3.5.5 we found that the mean of Y is µy = 21.49. The variance of Y is VAR(Y) = of = (20 – 21.49) x Pr{Y = 20} 21) %3D + (21 – 21.49)? x Pr{Y + (22 – 21.49)? x Pr{Y = 22} + (23 – 21.49) x Pr{Y = 23} = (-1.49) x 0.03 + (-.49) x 0.51 + (0.51) x 0.40 + (1.51)² × 0.06 = 2.2201 x 0.03 + .2401 x 0.51 + .2601 x 0.40 + 2.2801 x 0.06 = 0.066603 + 0.122451 + 0.10404 + 0.136806 = 0.4299. The standard deviation of Y is ay = V0.4299 - 0.6557. %3Darrow_forwardIn a study conducted on human height, heritability estimates that were initially done on children with an average age of 5 years old was 74%. Heritability estimates were again performed on the same individuals when they reached adulthood with an average of 40 years old. The result was 30%. Explain the results.arrow_forwardHotchkiss and Marmur noted that the percentage of cotransformation was higher than would be expected on a random basis. For example, the results show that 2.6% of the cells were transformed into M and 4% were transformed into S. If the M and S traits were inherited independently, the expected probability of cotransformation of M and S (M S) would be 0.026× 0.04 = 0.001, or 0.1%. However, they observed 0.41% M S cotransformants, four times more than they expected. What accounts for the relatively high frequency of cotransformation of the traits they observed?arrow_forward
- Upon further scrutiny of the pine beetles over generations, you discover that they have far more than 11 shades of green—in fact, they seem to have a continuous distribution of shades of green color. You take this population and breed them in two different locations: first in a terrarium in the lab, and then in a tree. In which of these two locations will you get a higher heritability value when you measure the variance of phenotypes in the next generation? a) Higher heritability value in the lab. b) The heritability value will be the same because the beetles are the same. c)Higher heritability value in the tree. d)The answer cannot be determined from the information given.arrow_forwardThe locus in a species of wild apples affects the redness of the fruit. There are two alleles, V1 and V2. V2V2 individuals have a redness index of 10 on average, V1V2 individuals have a redness index of 12 on average, and V1V1 individuals have a redness index of 18 on average. (a) Compute the additive (a) and dominance (d) effects of this locus. (b) Compute the population mean spot number if V1 is at a frequency of 0.30.arrow_forwardIn an assessment of learning in Drosophila, flies were trained to avoid certain olfactory cues. In one population, a mean of 8.5 trials was required. A subgroup of this parental population that was trained most quickly (mean = 6.0) was interbred, and their progeny were examined. These flies demonstrated a mean training value of 7.5. Calculate realized heritability for olfactory learning in Drosophila.arrow_forward
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