Textbook Question
Contrast the various categories of repetitive DNA.
31
views
Ch. 11 - Chromosome Structure and DNA Sequence Organization
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 11, Problem 15
Mammals contain a diploid genome consisting of at least 10⁹ bp. If this amount of DNA is present as chromatin fibers, where each group of 200 bp of DNA is combined with 9 histones into a nucleosome and each group of 6 nucleosomes is combined into a solenoid, achieving a final packing ratio of 50, determine:
(a) the total number of nucleosomes in all fibers,
(b) the total number of histone molecules combined with DNA in the diploid genome, and
(c) the combined length of all fibers.
Verified step by step guidance1
Identify the total amount of DNA base pairs (bp) given, which is at least 10⁹ bp for the diploid genome.
Calculate the total number of nucleosomes by dividing the total base pairs by the number of base pairs per nucleosome. Since each nucleosome contains 200 bp, use the formula: \(\text{Number of nucleosomes} = \frac{10^{9} \text{ bp}}{200 \text{ bp/nucleosome}}\).
Determine the total number of histone molecules by multiplying the number of nucleosomes by the number of histones per nucleosome. Given that each nucleosome has 9 histones, use: \(\text{Total histones} = \text{Number of nucleosomes} \times 9\).
Calculate the combined length of all chromatin fibers before packing. First, find the length of DNA per base pair (approximately 0.34 nm per bp), then multiply by the total number of base pairs: \(\text{DNA length} = 10^{9} \text{ bp} \times 0.34 \text{ nm/bp}\).
Adjust the length of the fibers to account for the packing ratio of 50, which means the chromatin fiber length is reduced by a factor of 50 compared to the extended DNA length. Use: \(\text{Fiber length} = \frac{\text{DNA length}}{50}\).
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
1mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleosome Structure and Composition
A nucleosome is the fundamental unit of chromatin, consisting of approximately 200 base pairs of DNA wrapped around a histone octamer made up of 8 histone proteins. The question states 9 histones per nucleosome, which may include an additional linker histone. Understanding nucleosome composition is essential to calculate the total number of nucleosomes and histones in the genome.
Recommended video:
Guided course
07:10
Chromosome Structure
Chromatin Fiber Organization and Solenoid Model
Chromatin fibers are formed by nucleosomes arranged into higher-order structures. Six nucleosomes fold into a solenoid fiber, which compacts DNA further. This hierarchical organization affects the overall length and packing ratio of DNA, crucial for determining the combined length of chromatin fibers.
Recommended video:
Guided course
07:55Histone Protein Modifications
DNA Packing Ratio and Genome Size
The packing ratio describes how much the DNA length is reduced by chromatin folding. Given a diploid genome size of 10⁹ base pairs and a packing ratio of 50, this ratio helps convert the total DNA length into the length of compacted chromatin fibers, enabling calculations of fiber length and nucleosome numbers.
Recommended video:
Guided course
08:41Sequencing Difficulties
Related Practice
Textbook Question
Define satellite DNA. Describe where it is found in the genome of eukaryotes and its role as part of chromosomes.
73
views
Textbook Question
Contrast the structure of SINE and LINE DNA sequences. Why are LINEs referred to as retrotransposons?
1069
views
Textbook Question
Assume that a viral DNA molecule is a 50-µm-long circular strand with a uniform 20-Å diameter. If this molecule is contained in a viral head that is a 0.08-µm-diameter sphere, will the DNA molecule fit into the viral head, assuming complete flexibility of the molecule? Justify your answer mathematically.
472
views
Textbook Question
How many base pairs are in a molecule of phage T2 DNA 52-µm long?
836
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?
722
views