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?
744
views
Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes
Klug10th EditionEssentials of GeneticsISBN: 9780135588789
Not the one you use?Change textbookSelect a different textbook
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 1c
How do we know that crossing over results from a physical exchange between chromatids?
Verified step by step guidance1
Understand the concept of crossing over: it is the process during meiosis where homologous chromosomes exchange segments, leading to genetic recombination.
Recognize that physical exchange means actual breakage and rejoining of DNA strands between non-sister chromatids of homologous chromosomes.
Examine cytological evidence: during meiosis, chiasmata (visible points where chromatids appear to be physically connected) can be observed under a microscope, indicating sites of crossing over.
Consider experimental evidence from genetic mapping: the frequency of recombinant offspring correlates with the physical distance between genes, supporting the idea of physical exchange.
Review molecular evidence such as the detection of DNA double-strand breaks and the involvement of specific enzymes (e.g., recombinases) that mediate the cutting and rejoining of DNA during crossing over.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
2mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Crossing Over
Crossing over is the process during meiosis where homologous chromosomes exchange segments of their chromatids. This exchange increases genetic diversity by producing new combinations of alleles. It occurs during prophase I and is essential for proper chromosome segregation.
Recommended video:
Guided course
05:19
Discovery of Crossing Over
Physical Exchange of Chromatids
The physical exchange refers to the actual breakage and rejoining of DNA strands between non-sister chromatids. Cytological evidence, such as chiasmata observed under a microscope, demonstrates that chromatids physically swap segments, confirming crossing over is a tangible molecular event.
Recommended video:
Guided course
04:35Chromatin
Cytological and Genetic Evidence
Microscopic observations of chiasmata and genetic mapping data showing recombination frequencies support the physical exchange model. The correlation between chiasmata number and recombination rates provides strong evidence that crossing over results from physical chromatid exchanges.
Recommended video:
Guided course
03:45Descriptive Genetics
Related Practice
Textbook Question
How do we know that specific genes are linked on a single chromosome, in contrast to being located on separate chromosomes?
510
views
Textbook Question
How do we know that sister chromatids undergo recombination during mitosis?
453
views
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.
644
views
Textbook Question
Describe the cytological observation that suggests that crossing over occurs during the first meiotic prophase.
828
views