Textbook Question
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
Explain the meaning of this I value.
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Ch. 5 - Genetic Linkage and Mapping in Eukaryotes
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
Chapter 5, Problem 16c
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
Why is the recombination frequency for the outside pair of genes not equal to the sum of recombination frequencies between the adjacent gene pairs?
Verified step by step guidance1
Step 1: Understand the problem. The question asks why the recombination frequency for the outside pair of genes is not equal to the sum of recombination frequencies between adjacent gene pairs. This involves analyzing the genetic linkage and recombination events between the genes G, L, and T.
Step 2: Identify parental and recombinant genotypes. Parental genotypes are those that match the original combinations of alleles in the parents (Gg Ll Tt and gg ll tt). Recombinant genotypes are those that result from crossing over during meiosis, leading to new combinations of alleles.
Step 3: Calculate recombination frequencies for adjacent gene pairs. To do this, determine the number of recombinant offspring for each pair of adjacent genes (G-L and L-T) and divide by the total number of offspring. Use the formula: recombination frequency = (number of recombinant offspring / total offspring) × 100.
Step 4: Calculate the recombination frequency for the outside pair of genes (G-T). This involves identifying recombinant offspring for the G-T pair and using the same formula as in Step 3.
Step 5: Explain the discrepancy. The recombination frequency for the outside pair of genes (G-T) is not equal to the sum of recombination frequencies for adjacent pairs (G-L and L-T) because double crossover events can occur. These double crossovers affect the observed recombination frequencies, as they can restore parental combinations, making the recombination frequency appear lower than expected.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Linkage and Recombination
Linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together. Recombination occurs during meiosis when homologous chromosomes exchange genetic material, leading to new allele combinations. The recombination frequency is a measure of how often recombination occurs between two genes, which can affect the inheritance patterns observed in offspring.
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Chi Square and Linkage
Test Cross
A test cross involves breeding an individual with a dominant phenotype but unknown genotype with a homozygous recessive individual. This method helps determine the genotype of the dominant individual based on the phenotypes of the offspring. In the context of the question, the test cross reveals the segregation and recombination of alleles, providing insights into gene linkage.
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Chi-Square Analysis
Chi-square analysis is a statistical method used to determine if there is a significant difference between observed and expected frequencies in genetic crosses. It helps assess whether the deviations from expected ratios are due to chance or indicate linkage between genes. This analysis is crucial for interpreting the results of the test cross and understanding the genetic relationships among the offspring.
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Related Practice
Textbook Question
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
What is the order of these three linked genes?
Textbook Question
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
What is the interference value for this data set?
Textbook Question
In a diploid plant species, an F₁ with the genotype Gg Ll Tt is test-crossed to a pure-breeding recessive plant with the genotype gg ll tt. The offspring genotypes are as follows:
Calculate the recombination frequency between each pair of genes.
Textbook Question
Three dominant traits of corn seedlings, tunicate seed (T-), glossy appearance (G-), and liguled stem (L-), are studied along with their recessive counterparts, nontunicate (tt), nonglossy (gg), and liguleless (ll). A trihybrid plant with the three dominant traits is crossed to a nontunicate, nonglossy, liguleless plant. Kernels on ears of progeny plants are scored for the traits, with the following results:
Could all three genes be carried on the same chromosome? Discuss why or why not.
Textbook Question
The table given here lists the arrangement of alleles of linked genes in dihybrid organisms, the recombination frequency between the genes, and specific gamete genotypes. Using the information provided, determine the expected frequency of the listed gametes. Assume one map unit equals 1% recombination and, when three genes are involved, interference is zero.
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