Skip to main content
Pearson+ LogoPearson+ Logo
Ch. 12 - DNA Organization in Chromosomes
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 12 - DNA Organization in ChromosomesProblem 22
Chapter 12, Problem 22

An article entitled 'Nucleosome Positioning at the Replication Fork' states: 'both the 'old' randomly segregated nucleosomes as well as the 'new' assembled histone octamers rapidly position themselves (within seconds) on the newly replicated DNA strands' [Lucchini et al. (2002)]. Given this statement, how would one compare the distribution of nucleosomes and DNA in newly replicated chromatin? How could one experimentally test the distribution of nucleosomes on newly replicated chromosomes?

Verified step by step guidance
1
Understand the concept of nucleosomes: Nucleosomes are structural units of chromatin, consisting of DNA wrapped around histone proteins. During DNA replication, both 'old' nucleosomes and 'new' histone octamers are distributed onto the newly synthesized DNA strands.
Compare the distribution of nucleosomes and DNA: To analyze the distribution, consider that 'old' nucleosomes are randomly segregated, while 'new' histone octamers are assembled and positioned on the replicated DNA. This suggests a mix of pre-existing and newly formed nucleosomes on the chromatin.
Design an experimental approach: Use chromatin immunoprecipitation (ChIP) to isolate nucleosomes from newly replicated DNA. Label 'old' histones with a specific marker (e.g., fluorescent or radioactive labeling) prior to replication and track their presence on the replicated DNA.
Analyze the results: Perform sequencing or imaging techniques to determine the spatial distribution of 'old' and 'new' nucleosomes along the replicated DNA. Compare the patterns to assess whether the distribution is random or follows specific positioning rules.
Validate findings: Use additional methods such as mass spectrometry to confirm the identity of histones (old vs. new) and their association with specific DNA regions. This ensures the reliability of the experimental results.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1m
Was this helpful?

Key Concepts

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

Nucleosome Structure and Function

Nucleosomes are the fundamental units of chromatin, consisting of DNA wrapped around histone proteins. They play a crucial role in packaging DNA into a compact structure, regulating gene expression, and facilitating DNA replication. Understanding nucleosome positioning is essential for analyzing how DNA is organized and accessed during replication and transcription.
Recommended video:
Guided course
08:26
Functional Genomics

Chromatin Dynamics during DNA Replication

During DNA replication, chromatin undergoes significant remodeling to accommodate the newly synthesized DNA strands. This involves the disassembly of existing nucleosomes and the assembly of new histone octamers. The dynamics of nucleosome positioning are critical for maintaining genomic stability and ensuring proper gene regulation in the newly replicated chromatin.
Recommended video:
Guided course
11:59
Steps to DNA Replication

Experimental Techniques for Nucleosome Mapping

To experimentally test the distribution of nucleosomes on newly replicated chromosomes, techniques such as chromatin immunoprecipitation (ChIP) and sequencing (ChIP-seq) can be employed. These methods allow researchers to identify specific nucleosome positions and their occupancy on DNA, providing insights into chromatin structure and function during replication.
Recommended video:
Guided course
07:11
Mapping with Markers
Related Practice
Textbook Question

Cancer can be defined as an abnormal proliferation of cells that defy the normal regulatory controls observed by normal cells. Recently, histone deacetylation therapies have been attempted in the treatment of certain cancers [reviewed by Delcuve et al. (2009)]. Specifically, the FDA has approved histone deacetylation (HDAC) inhibitors for the treatment of cutaneous T-cell lymphoma. Explain why histone acetylation might be associated with cancer and what the rationale is for the use of HDAC inhibitors in the treatment of certain forms of cancer.

522
views
Textbook Question
In a study of Drosophila, two normally active genes, w⁺ (wild-type allele of the white-eye gene) and hsp26 (a heat-shock gene), were introduced (using a plasmid vector) into euchromatic and heterochromatic chromosomal regions, and the relative activity of each gene was assessed [Sun et al. (2002)]. An approximation of the resulting data is shown in the following table. Which characteristic or characteristics of heterochromatin are supported by the experimental data?Gene Activity (relative percentage) _Euchromatin Heterochromatinhsp26 100% 31%w⁺ 100% 8%
510
views
Textbook Question

While much remains to be learned about the role of nucleosomes and chromatin structure and function, recent research indicates that in vivo chemical modification of histones is associated with changes in gene activity. One study determined that acetylation of H3 and H4 is associated with 21.1 percent and 13.8 percent increases in yeast gene activity, respectively, and that histones associated with yeast heterochromatin are hypomethylated relative to the genome average [Bernstein et al. (2000)]. Speculate on the significance of these findings in terms of nucleosome–DNA interactions and gene activity.

794
views
Textbook Question

The human genome contains approximately 106 copies of an Alu sequence, one of the best-studied classes of short interspersed elements (SINEs), per haploid genome. Individual Alu units share a 282-nucleotide consensus sequence followed by a 3'-adenine-rich tail region [Schmid (1998)]. Given that there are approximately 3 x 109 base pairs per human haploid genome, about how many base pairs are spaced between each Alu sequence?

715
views
Textbook Question

The following is a diagram of the general structure of the bacteriophage chromosome. Speculate on the mechanism by which it forms a closed ring upon infection of the host cell.

642
views
Textbook Question

Microsatellites are currently exploited as markers for paternity testing. A sample paternity test is shown in the following table in which ten microsatellite markers were used to test samples from a mother, her child, and an alleged father. The name of the microsatellite locus is given in the left-hand column, and the genotype of each individual is recorded as the number of repeats he or she carries at that locus. For example, at locus D9S302, the mother carries 30 repeats on one of her chromosomes and 31 on the other. In cases where an individual carries the same number of repeats on both chromosomes, only a single number is recorded. (Some of the numbers are followed by a decimal point, for example, 20.2, to indicate a partial repeat in addition to the complete repeats.) Assuming that these markers are inherited in a simple Mendelian fashion, can the alleged father be excluded as the source of the sperm that produced the child? Why or why not? Explain.

988
views