# Hello, I need help answering this question regarding additive

### Question Description:

Hello, I need help answering this question regarding additive alleles and I am confused on how to go about answering this. It is Question number 5 in my lab manual. Kelyte starfish, in the galaxy Voronia, have arm lengths that are determined by two unlinked loci, A and B. A partial set of two-locus genotypes and their corresponding armlengths are presented in the table below. a. Do the two loci act additively? Explain. b. Derive a formula to determine arm length as a function of each two-locus genotype. Fill in the table the attached table of values. Please help! Thank you ATTACHMENT PREVIEW Download attachment 7 pages Lab-06-Manual-Quantitative-Genetics.pdf Laboratory 06 – Quantitative Genetics INTRODUCTION For most of this course we have been dealing with traits showing just two distinct phenotypes. For example: HAPPY individuals: Vertical or horizontal stripes, Eye color: white or red in fruit flies, Vulcan Sehlats: long teeth or short teeth. When phenotypes fall into distinct categories that do not overlap, a trait is said to exhibit discontinuous variation. Many traits, however, show a continual range of phenotypes or continuous variation. For example, height, blood pressure, intelligence and skin color in humans are controlled by multiple genes. Another good example of continuous variation is beak size in Darwin’s finches. The study of the inheritance of traits that show continuous variation is called quantitative genetics. In order to study quantitative genetics it is useful to review elementary statistical measures such as mean ( X ), variance (Var) and standard deviation (sd). Here’s an example of how these parameters are used in a survey of beak size for finches on one island in the Galapagos Islands. Beak Size (x) Number of Birds (f) f(x) __________________________________________________________________ 19 mm 1 19 20 mm 9 180 21 mm 17 357 22 mm 28 616 23 mm 14 322 24 mm 11 264 25 mm 4 100 __________________________________________________________________ TOTAL 84 1858 The average bill size (mean) is the f(x) divided by the total number of birds (N). Thus, X = Σ f(x) / N = 1858 / 84 = 22.1 mm. 1|P age We are also interested in knowing something about the dispersion of values around the mean. The parameter that represents this dispersion is the variance (Var). The variance is the sum of the squared deviations (d2) from the mean divided by N-1. A high variance means that there is a great deal of dispersion, while a low variance suggests that the individual values are relatively close to the mean. Var = Σ f(d2) / (N-1). In our example: Beak Size freq. d( X – X) d2 (freq) (d2) _________________________________________________________________ 19 mm 1 3.1 9.6 9.6 20 mm 9 2.1 4.2 37.8 21 mm 17 1.1 1.2 20.4 22 mm 28 0.1 0.01 0.28 23 mm 14 – 0.9 0.81 11.3 24 mm 11 – 1.9 3.63 39.9 25 mm 4 – 2.9 8.4 33.6 _________________________________________________________________ TOTAL = 152.5 Var = Σ f(d2) /(N-1) = 152.5 / 83 = 1.84. We are often more interested in dispersion of values around the mean that have the same unit value as the mean (millimeters, in this case). The parameter used to express dispersion in the same units as the mean is called the standard deviation (sd). SD = ( Var ) = 1.84 = 1.36. The standard deviation describes the area under a normal curve. One standard deviation around the mean equals 66% of the area. Two standard deviations around the mean encompasses 95.4% of the area under the curve. Importantly, a value of 1.96 standard deviations is equal to 95% of the area of a normal curve. This number is used to determine the 95% confidence level in a number of important statistical tests. Polygenic inheritance was first discovered by Nielsen in studies involving seed color in wheat. In a cross between a red and a white strain, he found a range of colors between red and white in the F2 generation. In his first experiment, he found a ratio of 15 colored (having some amount of red) to one pure white. In a second exper