Textbook Question
How was it established experimentally that the frequency of recombination (crossing over) between two genes is related to the distance between them along the chromosome?
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Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
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Table of contents
- Ch. 1 - Introduction to Genetics16
- Ch. 2 - Mitosis and Meiosis28
- Ch. 3 - Mendelian Genetics37
- Ch. 4 - Modification of Mendelian Ratios53
- Ch. 5 - Sex Determination and Sex Chromosomes32
- Ch. 6 - Chromosome Mutations: Variation in Number and Arrangement37
- Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes36
- Ch. 8 - Genetic Analysis and Mapping in Bacteria and Bacteriophages24
- Ch. 9 - DNA Structure and Analysis38
- Ch. 10 - DNA Replication29
- Ch. 11 - Chromosome Structure and DNA Sequence Organization22
- Ch. 12 - The Genetic Code and Transcription36
- Ch. 13 - Translation and Proteins27
- Ch. 14 - Gene Mutation, DNA Repair, and Transposition34
- Ch. 15 - Regulation of Gene Expression in Bacteria22
- Ch. 16 - Regulation of Gene Expression in Eukaryotes37
- Ch. 17 - Recombinant DNA Technology27
- Ch. 18 - Genomics, Bioinformatics, and Proteomics30
- Ch. 19 - The Genetics of Cancer21
- Ch. 20 - Quantitative Genetics and Multifactorial Traits37
- Ch. 21 - Population and Evolutionary Genetics45
Chapter 7, Problem 1b
How do we know that specific genes are linked on a single chromosome, in contrast to being located on separate chromosomes?
Verified step by step guidance1
Understand the concept of genetic linkage: genes that are located close together on the same chromosome tend to be inherited together because they are less likely to be separated by recombination during meiosis.
Perform a test cross or a dihybrid cross involving the two genes in question and observe the offspring phenotypes to determine the frequency of recombinant versus parental types.
Calculate the recombination frequency using the formula: \(\text{Recombination Frequency} = \frac{\text{Number of recombinant offspring}}{\text{Total number of offspring}} \times 100\%\).
Interpret the recombination frequency: if the frequency is significantly less than 50%, it suggests the genes are linked on the same chromosome; if it is close to 50%, the genes assort independently and are likely on different chromosomes.
Confirm linkage by repeating the experiment or using molecular techniques such as chromosome mapping or fluorescence in situ hybridization (FISH) to physically locate the genes on chromosomes.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Genetic Linkage
Genetic linkage refers to the tendency of genes located close together on the same chromosome to be inherited together during meiosis. Linked genes do not assort independently, which contrasts with genes on different chromosomes that follow Mendel's law of independent assortment.
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Chi Square and Linkage
Recombination and Crossing Over
Recombination occurs when homologous chromosomes exchange segments during meiosis, producing new allele combinations. The frequency of recombination between two genes indicates their physical distance on a chromosome; lower recombination rates suggest closer linkage.
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Test Cross and Genetic Mapping
A test cross involves breeding an individual heterozygous for certain genes with a homozygous recessive individual to observe offspring phenotypes. Analyzing offspring ratios helps determine if genes are linked and allows construction of genetic maps based on recombination frequencies.
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Related Practice
Textbook Question
How do we know that crossing over results from a physical exchange between chromatids?
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Textbook Question
How do we know that sister chromatids undergo recombination during mitosis?
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Textbook Question
Write a short essay that discusses how crossing over can be detected and how the resultant data provide the basis of chromosome mapping.
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