Textbook Question
What genetic process is occurring in a puff of a polytene chromosome? How do we know this experimentally?
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Ch. 12 - DNA Organization in Chromosomes
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 12, Problem 8
Describe the sequence of research findings that led to the development of the model of chromatin structure.
Verified step by step guidance1
Begin by understanding that early research identified DNA as the genetic material, but the physical form of DNA inside the nucleus was not yet clear. Scientists observed that DNA was associated with proteins, suggesting a complex structure.
Next, study the discovery of nucleosomes, where researchers found that DNA wraps around histone proteins forming bead-like structures. This was a key finding showing the first level of chromatin organization.
Then, explore how electron microscopy and biochemical experiments revealed that nucleosomes are connected by linker DNA, creating a 'beads-on-a-string' structure, which is the primary level of chromatin packing.
After that, examine how further research showed that this string of nucleosomes folds into a more compact 30-nanometer fiber, involving interactions between histone tails and linker DNA, representing a higher-order chromatin structure.
Finally, consider how ongoing studies demonstrated that chromatin can further loop and fold into even more complex structures, allowing DNA to be efficiently packed in the nucleus while still accessible for transcription and replication, leading to the current hierarchical model of chromatin organization.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Discovery of DNA and Histones
Early research identified DNA as the genetic material and histones as basic proteins associated with DNA. Understanding that DNA wraps around histones was crucial for recognizing how genetic material is compacted within the nucleus.
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Discovery
Nucleosome Model
The nucleosome was discovered as the fundamental unit of chromatin, where DNA is wrapped around a histone octamer. This model explained the first level of DNA packaging and provided insight into chromatin’s repeating structure.
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04:35Chromatin
Higher-Order Chromatin Structure
Subsequent research revealed that nucleosomes fold into more complex structures, such as the 30 nm fiber and looped domains, explaining how chromatin achieves further compaction and regulates gene accessibility.
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Related Practice
Textbook Question
During what genetic process are lampbrush chromosomes present in vertebrates?
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Textbook Question
Why might we predict that the organization of eukaryotic genetic material will be more complex than that of viruses or bacteria?
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Textbook Question
Describe the molecular composition and arrangement of the components in the nucleosome.
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Textbook Question
Describe the transitions that occur as nucleosomes are coiled and folded, ultimately forming a chromatid.
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Textbook Question
Provide a comprehensive definition of heterochromatin and list as many examples as you can.
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