Ch 17 - Quantitative Genetics
Select the statements that describe the change in distribution as the diameter of the flowering heads increases.
- The phenotypic variance of each genotype decreases with each successive generation. - As the diameter of the sunflower head increases, the mean increases. Explanation: The mean of the data is the average of the flowering head diameters. The variance is the average squared deviation of the flowering head diameters from their mean value.
Suppose that seed size in a particular plant species is a polygenic trait. A grower crosses two different pure-breeding varieties of plant, and measures seed size in the F1 progeny. She then backcrosses the F1 plants to one of the parental varieties and measures seed size in the backcross progeny. The grower finds that seed size in the backcross progeny has a higher variance than seed size in the F1 progeny. What is the most likely explanation for the higher seed size variability in the backcross progeny?
-The backcross progeny are not uniformly heterozygous at the seed size loci Explanation: -Polygenic: multiple genes involved -Any variance that occurs in pure-breeding is due to environmental factors -If you have an F1 that is heterozygous for all those genes, many different combinations will segregate in the backcross -There are more genotypes with the backcross of the heterozygous -the backcross progeny are not uniformly heterozygous at all seed size loci (this is actually the F1 progeny) -cell divisions and mutations were not discussed in the heritability section
If you eliminate all VE from the variance components, then VGE equals _____. phenotypic variance environmental variance 0 1
0 One way to calculate the broad-sense heritability is to eliminate one of the variance components. Since VP = VG + VE + VGE, if one eliminates environmental variance, VE, then VGE = 0, and VP = VG.
Flower color in the varieties of pea plants studied by Mendel is controlled by alleles at a single locus. A group of peas homozygous for purple flowers is grown in a garden. All flowers are purple, yet there is some variation in the intensity of the purple color. The estimated heritability for this observed variation in flower color would be _____. 0 1 0.75 0.5
0 The plants are homozygous for the single color locus; therefore, there is no genetic variance: VG = 0. Because broad-sense heritability is VG/VP, if VG is zero, then heritability is zero.
Classify each statement about the heritability of a phenotype according to the narrow-sense heritability value it describes.
0.0: - The phenotypic variance is determined by environmental variance - The phenotype of offspring is not related to the phenotypes of parents 0.5: - Half of the observed variation is due to the additive genetic effects of alleles 0.98: - Parents and their offspring share heritable phenotypes - Phenotypic differences result from genetic variation Explanation: -Narrow‑sense heritability takes into account both genetic variance and environmental variance.
Jillian is assessing variance in hamsters. If VP is 1000, VE is 160 and VGE is 500, what is the narrow-sense heritability value? Note that gene interaction and dominance variance are negligible. 0.5 0.34 0.66 0.16
0.34 Phenotypic inheritance is the culmination of the genetic variables (VGE, VI, VD, and VA) and the environmental variables (VE). The narrow-sense heritability evaluates the additive effect through VA. Using the formula for phenotypic inheritance, one can determine the components from the information given. The resulting narrow-sense heritability (h^2) = VA ÷ VP. From the variables, VA can be determined from the difference of VP from VE and VGE. This would result in VA as 1000 − (500 + 160) = 340. h^2 = 340/1000, or 0.34.
The kernel color in wheat is a continuous trait determined by two additive genes, each with two alleles, that equally contribute to kernel color determination. The red kernels are determined by two genes and two dominant alleles (R1R1R2R2), and white kernels are determined by two recessive alleles at the same two genes (r1r1r2r2). The duplicate dominant alleles R1 and R2 contribute equally to kernel color and cumulatively control the intensity of the red kernel phenotype. Both these alleles are dominant over the recessive white alleles r1 and r2. A true breeding red plant and true breeding white plant are crossed, and the resulting F1 progeny are selfed. What is the expected phenotypic ratio of the kernel progeny of the F2 offspring? Determine which statement best describes the relationship between the phenotypes of the r1r1R2r2 and r1R1r2r2 genotypes.
1:4:6:4:1 (1 red: 4 dark pink:6 pink: 4 light pink: 1 white) -The phenotypes of the r1r1R2r2 and r1R1r2r2 genotypes will be the same because the same number of dominant and recessive alleles are contributing in each genotype Explanation: -The color intensity of a kernel depends on the number of dominant alleles in the genotype.
What is the variance for this group of measurements? Round to the nearest hundredth. 4, 7, 7, 6, 9, 7, 8, 5, 6, 9, 7, 9 3.02 2.65 2.54 1.27
2.54 In determining the variance, the mean (xM) of the data points has to be found first. Once the mean value is found, the variance can be determined by the formula: (Σ (x value − xM)^2) ÷ (n − 1). The xM is determined by (4+7+7+6+9+7+8+5+6+9+7+9)/number of data points. The xM value is 7. From there, substituting in the numbers would yield an s^2 value of 2.54.
A plant breeder has determined these variances for yield of corn in his fields: Total phenotypic variance = 100 Additive genetic variance = 30 Dominance genetic variance = 50 Environmental variance = 20 The breeder wishes to improve yield. If the average yield in the starting population is 400 and he selects for breeding plants with an average yield of 500, what will be the expected average yield among the offspring of the selected plants? 400 450 420 430
430 Narrow-sense heritability is 0.30, so that the average yield would increase by 0.30 × 100 (selection differential) = 30 units above the population mean of 400.
What is the variance for this group of measurements? 4, 7, 7, 2, 9, 7 6 32 6.4 7
6.4 To calculate the variance, subtract the mean from each measurement and square the value obtained, add all of these squared deviations together and divide that sum by the number of original measurements minus 1. The variance should be 6.4. 4+7+7+2+9+7 = 36/6 = 6. (4-6)^2 + (7-6)^2 + (7-6)^2 + (2-6)^2 + (9-6)^2 + (7-6)^2 = (-2)^2 + (1)^2 + (1)^2 + (-4)^2 + (3)^2 + (1)^2 = 4 + 1 + 1 + 16 + 9 + 1 / (6-1) = 32/5 = 6.4
What is the mean for this group of measurements? 4, 7, 7, 2, 9, 7, 8, 5, 6, 9, 7, 7 7.2 4 7 6.5
6.5 To find the mean, all the data sets must be added and then divided by the number of data sets known. So the mean would be (4+7+7+2+9+7+8+5+6+9+7+7)/number of data points.
The graph indicates the stem lengths observed in a plant population. What is the mean stem length in the plant population indicated in the graph?
8 cm (Center of distribution curve)
Refer to Figure 17.10. What is the mean flower length for parental strain B? 34.8 mm 40.5 mm 87.3 mm 93.3 mm
93.3 mm A measurement of 93.3 mm is the mean flower length of parental strain B, since it is the centermost value with the highest frequency. Mean flower length for parental strain A = 40.5 mm
Suppose that human skin color is polygenic with control by three gene pairs (A, B, and C). Each "dominant" allele (uppercase letter) adds a unit of pigment above a baseline minimum skin color (very light). Each "recessive" allele (lowercase letter) adds no pigment. Which of these genotypes would produce the same phenotype as AaBbCc? AABbcc AABbCC AaBbCC aabbcc
AABbcc AABbcc individuals would be three units darker than very light, which is the same as AaBbCc individuals.
Bipolar disorder is a psychiatric disorder with a strong hereditary basis, but the exact mode of inheritance is not known. Research has shown that siblings of patients with bipolar illness are more likely to develop the disorder than are siblings of unaffected persons. Findings from one study demonstrated that the ratio of bipolar brothers to bipolar sisters is higher when the patient is male than when the patient is female. In other words, relatively more brothers of bipolar patients also have the disease when the patient is male than when the patient is female. Determine what the evidence suggests about the inheritance of bipolar disorder.
An X‑linked locus may contribute to this disorder. Explanation: -Consider which mode of inheritance most often results in a skewed gender ratio of affected progeny.
Which of the two graphs best represents measurements of a quantitative characteristic? B A neither one is a quantitative characteristic it cannot be determined
B The image resembles a bell curve with points moving along the curvature. Since there are no defined holds, this image would prompt continuity in its scaling and support quantitative characteristics versus qualitative characteristics. Many characteristics vary continuously along a scale of measurement, exhibiting many overlapping phenotypes. Referred to as continuous/quantitative characteristics because any individuals phenotype must be described by quantitative measurement (Ex: height, weight, blood pressure, growth rate, seed weight, milk production). (1) Many are polygenic (influenced by genes at many loci; if many loci take part, many genotypes are possible, resulting in many different phenotypes). (2) Environmental factors affect phenotype because environmental variation results in a single genotype producing a range of phenotypes. (Most continuously varying characters are both polygenic and influenced by environmental factors = multi factorial) A discontinuous/qualitative characteristic exhibits only a few easily distinguishable characteristics.
What is the difference between meristic and continuous characteristics? Continuous characteristics have a theoretically infinite number of phenotypes in a continuum while meristic characteristics have a limited number of distinct phenotypes. Meristic characteristics are either present or absent, while continuous characteristics are everything in between. Continuous characteristics are typically controlled by one gene while meristic characteristics are controlled by many genes. Meristic characteristics are influenced by the environment while continuous characteristics are more influenced by the genes themselves.
Continuous characteristics have a theoretically infinite number of phenotypes in a continuum while meristic characteristics have a limited number of distinct phenotypes. Continuous characteristics can result in a plethora of phenotypes being expressed while meristic characteristics are limited to a few.
Consider how the traits are affected by genetic and environmental factors. Kernel color in a particular strain of wheat: Kernel color is either white, light red, or dark red in this strain of wheat. Two codominant alleles, which segregate at a single locus, determine these three phenotypes. Presence or absence of leprosy: Family pedigrees indicate that an increased susceptibility to leprosy is heritable. However, the increased susceptibility does not follow a Mendelian inheritance pattern. Repeat exposure to the bacterium that causes leprosy also increases the probability of having leprosy. Number of branches on a species of rose bush: Several loci control the formation of 4, 6, 8, or 10 branches in this species of rose bush. This rose bush species forms more than 8 branches per bush when the rainfall is high during a growing season. Skin color in humans: The broad range of human skin color is due to variations
Continuous: Skin color in human Meristic: Branches on a rose bush can vary depending on the variety of rose and the condition in which it grows Threshold: Presence or absence of leprosy Discontinuous: Kernel color in wheat Presence or absence of cystic fibrosis Number of fingers
If broad-sense heritability for a trait is very high and narrow-sense heritability is very low, which of these must be TRUE? Additive variance must be high relative to total phenotypic variance. Environmental variance must be high relative to total phenotypic variance. Genotypic-environmental covariance must be high relative to total phenotypic variance. Dominance variance must be high relative to total phenotypic variance.
Dominance variance must be high relative to total phenotypic variance. Dominance variance must be high relative to total phenotypic variance because total genetic variance must high and additive genetic variance is very low.
_____ and _____ allow for different genotypes to produce the same phenotype. Adaptations; heritability Mutations; recombination Dominance; epistasis Enhancement; variance
Dominance; epistasis Dominance dictates the expression of one particular set of genes while epistasis can suppress genes due to their interaction. The combination of the two would produce uniform individuals due to the lack of genetic variation.
Which hypothesis regarding the inheritance of continuously varying characteristics was ultimately supported by research? Genetic mutations cause qualitative traits to become quantitative traits. Mendelian principles acting on numerous genes could not explain the inheritance of quantitative characteristics. The inheritance of quantitative characteristics could be explained by Mendelian principles. Quantitative characteristics are controlled completely by genetic factors.
Genetic mutations cause qualitative traits to become quantitative traits. Genetic mutations can create many genotypes, which could reflect in many phenotypes being produced.
Suppose Lynn obtained two sets of seeds to investigate the environmental and genetic contributions that affect the flowering time of a particular plant. The first set was from a variety that was bred for heat tolerance; the seeds in this set were genetically identical. The second set was collected from wild plants and thus the seeds in this set were genetically different. She then planted the seeds in either a greenhouse or on a river bank and determined the time from planting to when the first flowers bloomed. The graphs show the distribution of flowering time under the growth conditions indicated. Label the graphs to indicate whether the variation in flowering time is due to environmental (𝑉E) or genetic factors (𝑉G). From the comparison in graph C of genetically identical and genetically different plants grown on the river bank, Lynn determined that the genetic variance was 4.66 and the environmental varia
Graph A: VE; Graph B: VE, VE; Graph C: VE, VG VE=2.40 VP= VG+VE = 4.66+23.6 = 28.26 Heritability = VG/VP = 4.66/29.26 = 0.165
A dairy farmer has a herd of cows that average 80 liters of milk production weekly. She selects 10 cows from this herd that produce closer to 100 liters weekly and interbreeds them. The narrow-sense heritability of milk production is estimated to be 0.62. The expected milk production in the offspring should be _____ than was observed in the entire herd. lower higher exactly 62 percent higher about the same
Higher. When the narrow-sense heritability is low, the offspring resemble little of the parents. Since the narrow-sense heritability is high, the yield would resemble the parents who produce more than the herd.
A breeder is breeding dogs to select for weight. The weight, in pounds, for the eight dogs in the population is shown in the chart. The mean weight of the population of dogs is 70 pounds. Classify each mating pair according to the effect of its offspring has on the mean weight of the population. A. 50 B. 70 C. 70 D. 90 E. 50 F. 70 G. 90 H. 70
Increase: C and D Stays the same: B and H, C and F Decrease: A and E, A and a 40 pound dog Explanation: -anything above 70 will increase, and anything below 70 will decrease the mean weight of the population
Refer to Figure 17.10. Based on the distribution graphs for the parental strains, is flower length in tobacco a continuous or discontinuous characteristic? It is continuous because flower length is completely determined by the environment. It is continuous because the two parental strains have a distribution of flower lengths. It is discontinuous because the distributions are normal. It is discontinuous because there are two distinct mean lengths for flower lengths.
It is continuous because the two parental strains have a distribution of flower lengths. The flower lengths for the parental strains are on a scaled value with no set intervals, so it would be deemed a continuous measure.
In his wheat kernel color experiment, Nilsson-Ehle crossed a plant with white kernels with a plant with purple kernels. Instead of seeing white or purple kernel plants in his F1 progeny, he saw plants with red kernels. What does this imply? Kernel color is controlled by one gene with influences of the environment. Kernel color is a qualitative trait. Kernel color is controlled by many genes. Kernel color could be controlled by many genes, or by one gene with influences of the environment.
Kernel color could be controlled by many genes, or by one gene with influences of the environment. Both the polygenic model and environmental influence can play a part in producing red kernels as their influence can change the phenotypes being observed in the group.
Suppose there are five genes in pumpkins that work additively to affect pumpkin size. A homozygous lowercase allele pumpkin, aabbccddee, weighs 20 lb. Each capitalized allele additively affects the final phenotype by either adding or subtracting weight from the base pumpkin size. The effect of a single capitalized allele is listed in the table. What would the potential size range be for pumpkin offspring produced from the cross between a parent with genotype AaBBCcddEe and a parent with Genotype AABbccDDEe?
Largest pumpkin: 36 lb Smallest pumpkin: 24 lb
Assume that the length of wheat leaves is controlled by three loci, each with two alleles: L and l, W and w, H and h. Determine the differences in leaf length between two homozygous strains of wheat. Assume each allele contributes equally to the length of the plant leaves. One homozygous strain, ll ww hh, has leaves that are 100 mm in length, and the other strain, LL WW HH, has 220 mm leaves. The two homozygous strains are crossed, and the resulting F1 are selfed to produce F2 progeny. What length will the leaves of the Ll Ww Hh genotype plant be? What proportion of the F2 progeny will have the same phenotype as the Ll Ww Hh genotype? Input answer as a decimal.
Length of leaves of Ll Ww Hh: 160 mm Proportion of F2 progeny: 0.3125
The domestic cat, Felis catus, is a domesticated furry creature often kept as a pet in many countries. Suppose a volunteer at a local animal shelter wanted to find out a little more about the cats in her care. The volunteer carefully measured the height for the 10 fully grown adult cats at her shelter. The height measurements were taken from the base of the foreleg to the shoulder. The table shows the results of the measurements. Calculate the mean, variance, and standard deviations for cat height for the sample of shelter cats. Report all your answers to two decimal points.
Mean: 9.79 in Variance: 3.8732 in^2 Standard deviation: 1.9671 in Mean: 10.5+13+7.7+7.5+9.55+10.5+10.85+12.3+8.15+7.85= 97.9/10 = 9.79 Variance: (10.5-9.79)^2 + (13-9.79)^2 + (7.7-9.79)^2 + (7.5-9.79)^2 + (9.55-9.79)^2 + (10.5-9.79)^2 + (10.85-9.79)^2 + (12.3-9.79)^2 + (8.15-9.79)^2 + (7.85-9.79)^2 = (10.5-9.79) = 0.71^2 = 0.5041 (13-9.79) = 3.21^2 = 10.3041 (7.7-9.79) = -2.09^2 = 4.3681 (7.5-9.79) = -2.29^2 = 5.2441 (9.55-9.79) = -0.24^2 = 0.0576 (10.5-9.79) = 0.71^2 = 0.5041 (10.85-9.79)= 1.06^2 = 1.1236 (12.3-9.79) = 2.51^2 = 6.3001 (8.15-9.79) = -1.64^2 = 2.6896 (7.85-9.79) = -1.94^2 = 3.7636 = 34.859/9 = 3.8732 Standard deviation: Sqrt(3.87) = 1.97 Explanation: -Variance is the discrepancy between the observed value and the mean, and the standard deviation measures how spread out the numbers are from the mean.
Researchers estimate that broad-sense heritability of IQ in Sweden is 0.8. Which of these conclusions is valid, assuming that the estimate is accurate? Most variance for IQ in Sweden is due to total genetic variance. In Sweden, the environment does not play a large role in determining the IQ of individuals. Enriching the environment of disadvantaged children in Sweden would not lead to a big improvement in performance on IQ tests. Broad-sense heritability of IQ in the United States probably is higher than 0.5.
Most variance for IQ in Sweden is due to total genetic variance. Broad-sense heritability is the proportion of variance due to total genetic variance.
Suppose that phenotypic variation in the tail length of mice is summarized in the table. Additive genetic variance (𝑉𝐴)= 0.5 Dominance genetic variance (𝑉𝐷)= 0.4 Genetic interaction variance (𝑉𝐼)= 0.2 Environmental variance (𝑉𝐸)= 0.3 Genetic‑environmental interaction variance (𝑉𝐺𝐸)= 0.0 What is the narrow-sense heritability (h^2) of tail length? What is the broad-sense heritability (H^2) of tail length?
Narrow-sense: 0.357 Broad-sense: 0.786 Explanation: -Narrow‑sense heritability includes only additive genetic effects. However, broad‑sense heritability includes all sources of genetic variation, such as dominance and interaction effects. -Narrow: h2= VA / (VA+VD+VI+VE+VGE) h2= 0.5 / (0.5+0.4+0.2+0.3+0) = 0.5/1.4 = 0.357 -Broad: A similar strategy is used to calculate broad-sense heritability, but instead the variable VG is used in place of VA. VG is the total variance due to all genetic effects, so it includes VA, VD, VI, and VGE. H2=VG / VP H2= (VA+VD+VI+VGE) / (VA+VD+VI+VE+VGE) H2= (0.5+0.4+0.2+0) / (0.5+0.4+0.2+0.3+0) = 1.1/ 1.4 = 0.7857
Suppose a researcher performed an experiment to determine the number of genes affecting fruit size in tomatoes. She crossed the domestic tomato, Lycopersicon esculentum, and the wild species, Lycopersicon cheesmanii, for two generations to obtain F2 individuals. Consider the table, which reports the fruit diameter and number of offspring obtained by the researcher in the F2 generation. In the parental lines, L. cheesmanii had a fruit diameter of 8 cm and L. esculentum had a fruit diameter of 16 cm. Calculate the total number of genes involved in fruit diameter in tomato's.
Number of genes: 4 To determine the total number of genes involved in fruit diameter in tomatoes, first calculate the proportion of individuals with one of the extreme phenotypes. In this experiment, the extreme phenotypes are the largest and the smallest fruit diameter values. For this data set, an example of an extreme value is 16 cm. According to the data collected, 1 out of 256 offspring exhibit the extreme phenotype of 16 cm. The proportion of individuals with this extreme phenotype is therefore 1/256. After calculating the proportion, 𝑝, of individuals with an extreme phenotype, solve for the number of genes, 𝑛, using the equation 𝑝 = (1/4)^𝑛 To solve for an exponent, take the natural log of both sides of the equation. The quotient rule of natural logarithms states the logarithm of the division of 𝑥 and 𝑦 is the difference of logarithm of 𝑥 and logarithm of 𝑦. Therefore, to solve for 𝑛, the equation can be rewritten as.. 𝑛 = (ln(1)−ln(256))/(ln(1)−ln(4)) 𝑛 = 4
Cross two plants with narrow flower diameters in the Artificial Selection interactive and observe the results. Complete the statement about the experimental data. Next select the correct conclusion regarding the relationship between parental and offspring flower diameters. Parents with narrow flower diameter produce offspring with _______ flowers on average that the parental generation. What kind of relationship is there between paternal and offspring flower diameter?
Parents with narrow flower diameter produce offspring with NARROWER flowers on average that the parental generation. Direct relationship.
Suppose that three loci, each with two alleles (A and a, B and b, C and c), determine the differences in height between two homozygous strains of a plant. These genes are additive and equal in their effects on plant height. One strain (aa bb cc) is 10 cm in height. The other strain (AA BB CC) is 22 cm in height. The two strains are crossed, and the resulting F1 are interbred to produce F2 progeny. Match the F2 phenotypes and expected proportions of progeny.
Phenotype (Height). Proportion of F2 10 cm. 1/64 12 cm. 6/64 14 cm. 15/64 16 cm. 20/64 18 cm. 15/64 20 cm. 6/64 22 cm. 1/64 Explanation: -Consider using a Punnett square to represent the F2 progeny.
Looking at the results from a cross between two red kernel plants, how did Nilsson-Ehle determine that the environment did not play a significant role in wheat kernel color? There were too many phenotypes. As the dose of pigment increased, the phenotype got darker. The same genotype did not give rise to different phenotypes. There were too many genotypes.
The same genotype did not give rise to different phenotypes. The production of like phenotypes with the same genotype demonstrates that only the genotype controlled the phenotype that was produced.
Refer to Figure 17.10. The distribution of the F2 generation has a greater variance than both the F1 generation and parental generations. What does this mean? Flower length is completely determined by environmental factors. There are different genotypes present in the F2 generation. The F2 generation has a different mean than the F1 generation. The environment has a greater effect on the F2 generation than the F1 generation.
There are different genotypes present in the F2 generation. Different genotypes can yield different approximations in the flower length, which would increase the range of dispersion. This difference in dispersion would increase the degree of variance as seen in the distribution of F2.
Refer to Figure 17.10. In the graph of flower length for the F1 generation, the variance of the F1 generation was similar to the variance seen in the parental strains. What does this imply? There are different genotypes present in the F2 generation. Flower length is completely determined by environmental factors. The F2 generation has a different mean than the F1 generation. The environment has a greater effect on the F2 generation than the F1 generation.
There are different genotypes present in the F2 generation. The imitation of the distribution curve dictates that the F1and F2 generations have similar genotypes, but the extension in the F2 generation indicates that there are more genotypes present in that generation. This increase in genotypes allows for the variance to increase from the previous flower length pattern.
Some traits are considered to be quantitative even though phenotypes are classified only as present or absent. Genetic diseases often fit this description. What is the term used to describe this type of trait? What creates the underlying quantitative distribution for this type of trait?
Threshold trait -Genetic and environmental factors determine an individual's susceptibility to the trait. Susceptibility exhibits continuous variation, and individuals above a certain threshold express the trait. Explanation: -Consider that both genes and the environment influence the magnitude of a quantitative trait. One example of this is the disorder phenylketonuria (PKU). Brain damage results in individuals with high levels of blood phenylalanine, which result from a combination of genetic effects and diet. Consider what kind of mechanisms trigger brain damage in a disease such as PKU.
Suppose a farmer is interested in developing a breeding program on his chicken farm. The farmer would like to artificially select for egg weight, egg shape, shell color, and shell thickness. In a large population of his chickens, the farmer has measured these four continuous egg traits of interest and calculated their variances, which are shown in the table. (Narrow-sense heritability) Which trait would best respond to artificial selection by the farmer? Select all of the statements that identify how the farmer might utilize the information gained from his data.
Trait that would respond best to artificial selection: Shell color (59/112= 0.53) - Identify quantitative trait loci correlated to each trait examined in the chicken population after obtaining genetic sequence data for his chicken population. (Eventually. Identify IQTL if he has a mapping population, and genetic sequence data to map the phenotype of the different individuals) -Design an experiment to improve the shell thickness trait in the current chicken population by changing the farm environment (reducing the environmental variance)
Suppose that the narrow-sense heritability of ear length in Reno rabbits is 0.4. The phenotypic variance (VP) is 0.5, and the environmental variance (VE) is 0.1. Calculate the additive genetic variance (VA) for ear length in these rabbits.
VA = 0.2 Narrow-sense heritability: h^2 = VA/VP = 0.4 VP = 0.5, VA= 0.4(0.5) = 0.2
Is it possible for two populations of rabbits to both have polydactyly due to different mechanisms, as in the case where one has it due to a dominant trait and the other has it due to the environment? Yes, because Vp is composed of both genetic and environmental variance. Yes, because Vp is composed of both genetic and environmental variance and because heritability is specific to a defined population in a given environment. Yes, because heritability is specific to a defined population in a given environment. No, because they are the same species and thus have the same genetic makeup.
Yes, because Vp is composed of both genetic and environmental variance and because heritability is specific to a defined population in a given environment. The differentiation between the characteristics is influenced by genetic-environmental factors and heritability, which would show distinctions between two groups of the same species.
In which type of variance do offspring have a phenotype that is exactly intermediate between the parents? dominance genetic variance additive genetic variance genetic variance environmental variance
additive genetic variance Additive genetic variance is the additive effects of genes on the phenotype summed to determine the overall effect on the phenotype. This form of variance leads to an intermediate between the parent alleles
A tropical bird with a high-pitched song mates with a bird with a low-pitched song. The resulting offspring all have medium-pitched songs. What type of variance is happening in this case? additive genetic variance dominance genetic variance genetic variance environmental variance
additive genetic variance Additive genetic variance is the additive effects of genes on the phenotype summed to determine the overall effect on the phenotype. This form of variance leads to an intermediate between the parent alleles.
Which distribution curve has the greatest variance? [The horizontal axis represents length and ranges from 5 to 15, in increments of 1. The vertical axis represents frequency. A bell shaped curve labeled] They all have the same variance. curve C curve B curve A
curve C Curve C has the greatest spread of distribution, so it would also have the greatest variance out of the curves shown. Shown here are three distributions with the same mean but different variances. Greater variance, more spread out distribution is about the mean.
You have discovered a new bird. Molecular analysis reveals that breast feather color in this bird is controlled by a single gene with two alleles that segregate during meiosis. Breeding experiments, however, reveal a range of phenotypes resulting from each of the three genotypes that can occur. You are confused by this result until you remember that the relationship between genotype and phenotype can be complicated by the influence of the _____. additive genetic variation environment epistasis parents
environment The influence of environment on a trait can complicate the relationship between genotype and phenotype, resulting in a genotype producing a range of potential phenotypes. These phenotypes in fact may overlap, making it difficult to know whether different phenotypes are due to genetic or environmental differences.
Suppose that flower color in a particular plant species is controlled equally by two gene pairs that assort independently, and suppose that the environment does not influence the trait. Also suppose that each dominant allele contributes a unit of red pigment above a baseline minimum of no red pigment (white color). How many different flower colors (including white and different shades of red) would be expected among the offspring of AaBb × AaBb? two three five one
five There are five phenotypes expected among the offspring. They are white (aabb), light red (Aabb, aaBb), medium red (AAbb, AaBb, aaBB), medium-dark red (AABb, AaBB), and dark red (AABB).
A dairy farmer only breeds the cows in his herd that have shown high milk production. The mean milk production of the offspring will be: higher than that of the breeders as long as milk production is genetically varied. lower than that of the breeders because milk production is not genetically varied. higher than that of the breeders even if milk production is not genetically varied. the same as that of the breeders.
higher than that of the breeders as long as milk production is genetically varied. This selective breeding will alter the genetic variation of this population toward a phenotype of higher milk production.
Genome-wide association studies have been used to locate genes involved in quantitative characteristics associated with: disease types in plants. diets in humans. hormone levels in animals. number of ears of corn.
hormone levels in animals. Hormone levels can aid in dictating the traits and behaviors shared by animals. Using genome-wide association studies can determine whether certain attributes are contributable by their genetic profile.
In Nilsson-Ehle's experiment showing the inheritance of kernel color in wheat, that kind of distribution does the F2 generation have? skewed bimodal normal exponential
normal A normal distribution of quantity usually results in a symmetrical distribution of characteristics. Since there is an equal distribution on either side of the medium, it can be assumed to have a normal distribution.
In his wheat kernel color experiment, Nilsson-Ehle crossed a plant with white kernels with a plant with purple kernels. If kernel color was a qualitative trait, what would the F1 progeny look like? plants with white kernels only plants with purple kernels only plants with red kernels only plants with white kernels and plants with purple kernels
plants with white kernels and plants with purple kernels In the F1 progeny, since the kernel color is qualitative, it would only produce plants with white and purple kernels with no variation in between.
Examination of phenotypic ratios of progeny from a genetic cross will not work for quantitative characteristics for all of these reasons, EXCEPT that: quantitative characteristics are only inherited from one parent. environmental influences may contribute to phenotype. it is impossible to assign a genotype to an individual on the basis of phenotype alone. discontinuous characteristics may be exhibited.
quantitative characteristics are only inherited from one parent. Quantitative inheritance is influenced by both parents, so it would not limit the examination of phenotypic ratios of progeny in this way.
The genetic analysis of complex characteristics is called . . . quantitative genetics Mendelian genetics environmental genetics population genetics
quantitative genetics Quantitative genetics is the use of statistical procedures for analyzing complex characteristics in genetics.
If inheritance of a genetic marker is associated consistently with the inheritance of a particular phenotype, then that marker must be linked to: the environmental trait associated with the phenotype. the quantitative trait loci that affects that phenotype. the only gene causing that phenotype. the quantitative trait loci associated with the genotype.
the quantitative trait loci that affects that phenotype. The quantitative trait loci that affects the phenotype would determine the direct link between genetic markers and expression due to inheritance.
A horticulturist has two pure-breeding varieties of plants, one with white flowers and one with dark purple flowers. She crosses these parents and produces F1 progeny that are all intermediate in color. When the F1 plants are crossed to produce the F2 generation, the F2 progeny occur in white and several shades of purple. Out of 200 F2 progeny, two are white and four are dark purple. What is the most likely number of loci affecting flower color differences in this example, assuming equal and additive effects among the loci and that the loci are unlinked? two three one four
three If there are three loci segregating, then 1/64 of the F2 would be expected to resemble each parent. An average of 3 out of 200 F2 progeny resemble each parent, which is very close to 1/64.
The _____ is the statistic that describes how spread out a distribution is frequency normal distribution variance mean
variance The variance would determine how spread out the distribution is from the center.
