Exam 19: The Inheritance of Complex Traits

A behavioral biologist suspects the "N" locus to be involved in the learning ability of dogs.Learning is measured through a standardized test in which each dog can score from 0 (very poor)to 20 points (excellent).In an experiment,the mean score was 15.6 for dogs of genotype N/N,12.1 for dogs of genotype N/n and 7.2 for those of genotype n/n.What is the dominance/additivity ratio for this locus?

Imagine that an association mapping study revealed a particular variant of a SNP to be strongly associated with susceptibility to insomnia.From these data,you could infer that:

The mean weight in a population of fruit flies (Drosophila melanogaster)grown in identical conditions is 1.10 mg,and the standard deviation is 0.05.The heaviest fly in this population weighs 1.30 mg.The genetic deviation of this individual is:

When all of the variation in a population is due to environmental sources and there is no genetic variation,broad sense heritability (H²):

A quantitative geneticist measures the broad-sense heritability for bill length in an isolated population of ducks to be 0.75.This result suggests that:

Two pure lines of plants had mean heights of 26 cm and 42 cm,respectively.The F₁ had a mean of 34 cm and a variance of 20.The F₂ also had a mean of 34 but a variance of 60.The broad-sense heritability (H²)is:

You are studying the inheritance of antennae length in loppins using strains from British Columbia (BC)and Washington State (WA).BC loppins have,on average,much longer antennae than their WA counterparts.You have identified three QTLs that control this trait,and you obtained the following data. Which QTL(s)has/have the highest dominance effect?

A large number of genetically identical tomato plants are grown in a greenhouse.The mean height in this plant population is 84 cm,and the standard deviation is 2.5 cm.The variation in height within this population is most likely due to:

A population of beetles has a mean weight of 30 g.In a controlled,constant environment,individuals of 12 g are selected and allowed to interbreed,and their progeny have a mean weight of 21 g with a variance of 4.5 g².What is the additive variance in this experiment?

Suppose that gene A controls the synthesis of blue pigment in the petals of a flowering plant.Plants with genotype A/A produce blue pigment in their petals,while those with genotype A/a or a/a do not produce any blue pigment.The expected narrow-sense heritability (h²)for the production of blue pigment in this plant's flowers is:

A high variance indicates that:

Three inbred lines of potatoes are cultured in three different environments.The mean tuber weight for each line in each environment is reported below. Line A Line B Line C Environment 1: 131 93 160 Environment 2: 180 142 209 Environment 3: 97 59 126 a)What are the genetic deviations (g)for each of the three lines? b)What are the environmental effect (e)on tuber weight for each of the three environments?

Ten pairs of monozygotic twins were tested for their ability to solve geometry problems.The highest score obtained was 46 points,while the lowest was 6 points.The variance in geometry test score within the twenty subjects (measured in points²)was 208.The covariance for test score between twins was 125.In this study,the broad-sense heritability of geometry problem-solving ability is:

The amount of milk produced per day by a cow is an example of a:

The narrow-sense heritability (h²)for several traits in domesticated cattle follow: Trait Percent protein in milk 0.54 Feed efficiency 0.34 Milk yield 0.30 Calving interval 0.01 a)Which of these traits would be most responsive to artificial selection? b)Which would be least responsive?

Two highly inbred populations of the annual weed Capsella bursa-pastoris grow in adjacent fields.One field is mowed regularly;the other is never mowed.Seeds from the plants are taken to a greenhouse where they can be grown under uniform conditions.The mean height of plants at the time of flowering is measured for each population,and for the F₁ and F₂ generations from crosses between representatives of each population.The data from these experiments are as follows: Mean Variance (in cm) Mowed Field 6.2 4.0 Unmowed Field 13.6 10.2 10.2 12.6 10.4 20.3 a)How much of the observed variance in plant height at flowering is caused by the environment in which the plants are grown? b)How much of the variance is due to genotype? c)What is the broad-sense heritability (H²)for this character?

In a large flock of turkeys,average body weight is 5.0 kg.In a test to determine if the average weight of the flock can be increased by selective breeding,6.2 kg birds are removed and allowed to interbreed.Their progeny have an average weight of 5.2 kg.Calculate the narrow-sense heritability (h²).

Presume that the number of leaves in clovers is controlled by the combined actions of two genes,A and B,with no contributions from the environment.A/A results in four leaves,A/a in three leaves,and a/a in two leaves.Moreover,the genotypes B/B and B/b result in one additional leaf (b/b has no effect on leaf number). a)Based on the above information:

You are studying a highly inbred strain of barley.After many generations of inbreeding,you now assume that the genetic variation is zero.Suppose that you raise many individuals of your barley strain in a field in southeastern Michigan and then measure their height after one month of growth.You find that the variance in their height is 4.0.The broad-sense heritability of this trait is 0.From this particular study you can conclude that:

Which of the following has more important value to the plant or animal breeder?