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Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 20, Problem 43a

There are usually five or more colors of candy in each bag. Sort the candies by color, and if your bag has more than four colors, eat the least frequent color or colors. Once that is done, calculate the frequencies of the four remaining colors. Assume these frequencies represent four alleles of a gene, and use the description of the H-W equilibrium for more than two alleles for assistance.
Using a different one of the following variables for each color frequency, write out the expected results of a quadrinomial expansion of the expression (p+q+r+t)².

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Sort the candies by color and count the frequency of each color. Identify the least frequent color(s) if there are more than four colors, and remove them from consideration. This leaves you with four colors.
Assign a variable to represent the frequency of each of the four remaining colors. For example, let p, q, r, and t represent the frequencies of the four colors.
Recall the Hardy-Weinberg equilibrium principle for more than two alleles. The equilibrium states that the sum of the allele frequencies equals 1, so p + q + r + t = 1.
Write the quadrinomial expansion of the expression (p + q + r + t)². This represents the expected genotype frequencies in the population. Use the formula for expanding a binomial squared, but extend it to four terms: (p + q + r + t)² = p² + q² + r² + t² + 2pq + 2pr + 2pt + 2qr + 2qt + 2rt.
Interpret the terms in the expansion: p², q², r², and t² represent the homozygous genotypes for each allele, while 2pq, 2pr, 2pt, 2qr, 2qt, and 2rt represent the heterozygous genotypes formed by the combination of two different alleles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Allele Frequencies

Allele frequencies refer to how often a particular allele appears in a population compared to other alleles for the same gene. In the context of genetics, these frequencies are crucial for understanding genetic variation and can influence traits within a population. The frequencies are typically expressed as proportions or percentages, and they are foundational for applying models like the Hardy-Weinberg equilibrium.
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Hardy-Weinberg Equilibrium

The Hardy-Weinberg equilibrium is a principle that describes the genetic variation in a population that is not evolving. It provides a mathematical framework to predict allele and genotype frequencies under certain conditions, such as no mutation, migration, or selection. For more than two alleles, the equilibrium can be extended to account for multiple allele interactions, which is essential for analyzing complex genetic scenarios.
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Quadrinomial Expansion

Quadrinomial expansion involves expanding expressions that contain four variables, such as (p + q + r + t)². This mathematical process allows for the calculation of the probabilities of different combinations of alleles in a population. Understanding how to perform this expansion is important for predicting the expected genotype frequencies based on the allele frequencies derived from the candy sorting exercise.
Related Practice
Textbook Question

Put all the candies used in Problems 41 back into a single mound and then divide them into two piles, being sure that the frequencies of each color are the same in each pile. Make a note of the starting frequency of each color. Label one pile 'male' and the other pile 'female.'

Compare the starting frequency of each color with the frequency after drawing. Describe the observed differences and identify the evolutionary mechanism this exercise best emulates.

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Textbook Question

There are usually five or more colors of candy in each bag. Sort the candies by color, and if your bag has more than four colors, eat the least frequent color or colors. Once that is done, calculate the frequencies of the four remaining colors. Assume these frequencies represent four alleles of a gene, and use the description of the H-W equilibrium for more than two alleles for assistance.

Use this expansion to calculate the expected frequency of each possible genotype produced in a randomly mating population.

436
views
Textbook Question

Put all the candies used in Problems 41 back into a single mound and then divide them into two piles, being sure that the frequencies of each color are the same in each pile. Make a note of the starting frequency of each color. Label one pile 'male' and the other pile 'female.'

When all selection rounds have been completed, combine the two piles and determine the frequency of each color.

423
views
Textbook Question

Put all the candies used in Problems 41 back into a single mound and then divide them into two piles, being sure that the frequencies of each color are the same in each pile. Make a note of the starting frequency of each color. Label one pile 'male' and the other pile 'female.'

Repeat this process of blindly drawing one male and one female candy 12 to 15 times for each person in the group.

447
views