Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

20. Quantitative Genetics

Analyzing Trait Variance

Genetics

20. Quantitative Genetics

Analyzing Trait Variance

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3:54 minutes

Problem 29c

Textbook Question

A three-gene system of additive genes (A, B, and C) controls plant height. Each gene has two alleles (A and a, B and b, and C and c). There is dominance among the alleles of each gene, with alleles A, B, and C dominant over a, b, and c. Under this scheme, the dominant genotype for a gene contributes 10 cm to height potential, and the recessive genotype contributes 4 cm. What is the height potential of the F₁ progeny of the homozygous plants identified in (a) and (b) of this problem?

Verified step by step guidance

Step 1: Understand the genetic system described in the problem. Each gene (A, B, and C) has two alleles: a dominant allele (A, B, C) and a recessive allele (a, b, c). The dominant allele contributes 10 cm to plant height, while the recessive allele contributes 4 cm.

Step 2: Determine the genotypes of the homozygous parent plants mentioned in parts (a) and (b). Homozygous means both alleles for each gene are the same. For example, one parent could be homozygous dominant (AA, BB, CC), and the other could be homozygous recessive (aa, bb, cc).

Step 3: Predict the genotype of the F₁ progeny. When crossing a homozygous dominant parent (AA, BB, CC) with a homozygous recessive parent (aa, bb, cc), the F₁ progeny will inherit one dominant allele and one recessive allele for each gene, resulting in a heterozygous genotype (Aa, Bb, Cc).

Step 4: Calculate the height contribution of each gene in the F₁ progeny. Since the F₁ progeny are heterozygous (Aa, Bb, Cc), the dominant allele in each gene will determine the height contribution. For each gene, the dominant allele contributes 10 cm.

Step 5: Add the height contributions from all three genes to determine the total height potential of the F₁ progeny. Sum the contributions from the dominant alleles of genes A, B, and C to find the total height potential.

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Key Concepts

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

Additive Gene Action

Additive gene action refers to the cumulative effect of multiple genes on a single trait, where each gene contributes a specific amount to the phenotype. In this case, the three genes (A, B, and C) each add to the plant height, with dominant alleles contributing more than recessive ones. Understanding this concept is crucial for predicting the overall phenotype based on the genotypes of the parents.

Dominance and Alleles

Dominance describes the relationship between alleles, where a dominant allele masks the effect of a recessive allele in a heterozygous genotype. In this scenario, alleles A, B, and C are dominant over their respective recessive alleles a, b, and c. Recognizing which alleles are dominant helps in determining the potential contributions to the phenotype from each gene.

Genotype to Phenotype Conversion

The conversion from genotype to phenotype involves translating the genetic makeup (genotype) into observable traits (phenotype). In this problem, the height potential is calculated based on the genotypes of the homozygous parent plants, where each dominant allele contributes 10 cm and each recessive allele contributes 4 cm. This understanding is essential for calculating the expected height of the F₁ progeny.

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Related Practice

Textbook Question

A three-gene system of additive genes (A, B, and C) controls plant height. Each gene has two alleles (A and a, B and b, and C and c). There is dominance among the alleles of each gene, with alleles A, B, and C dominant over a, b, and c. Under this scheme, the dominant genotype for a gene contributes 10 cm to height potential, and the recessive genotype contributes 4 cm.What is the height potential of a plant that is homozygous for all three recessive alleles?

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Textbook Question

A three-gene system of additive genes (A, B, and C) controls plant height. Each gene has two alleles (A and a, B and b, and C and c). There is dominance among the alleles of each gene, with alleles A, B, and C dominant over a, b, and c. Under this scheme, the dominant genotype for a gene contributes 10 cm to height potential, and the recessive genotype contributes 4 cm. What is the height potential of a plant that is homozygous for all three dominant alleles?

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Textbook Question

A total of 20 men and 20 women volunteer to participate in a statistics project. The height and weight of each subject are given in the table. Calculate the mean, variance, and standard deviation for height and weight in men and women.

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Textbook Question

A total of 20 men and 20 women volunteer to participate in a statistics project. The height and weight of each subject are given in the table. Compare the numerical values with the visual distribution of heights and weights you drew in the histograms and describe whether you think your visual impression matches the numerical values.

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Textbook Question

A three-gene system of additive genes (A, B, and C) controls plant height. Each gene has two alleles (A and a, B and b, and C and c). There is dominance among the alleles of each gene, with alleles A, B, and C dominant over a, b, and c. Under this scheme, the dominant genotype for a gene contributes 10 cm to height potential, and the recessive genotype contributes 4 cm. What are the phenotypes and proportions of each phenotype among the F₂?

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Textbook Question

A total of 20 men and 20 women volunteer to participate in a statistics project. The height and weight of each subject are given in the table. Draw one histogram for the height of the subjects and a separate histogram for weight. Use different colors for men and women so that you can visually compare the distributions by sex and plot weights in 10-lb intervals (i.e., 90–99 lb, 100–109 lb, 110–119 lb, etc.).

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Multiple Choice

Which of the following represent trait variation caused from genetic variation?

If you wanted to identify what proportion of trait variation is due to the environment, you would do what?

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