Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 12, Problem 12PDQ
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 nucleo-some 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.
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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.
You have discovered a new species of plant. You isolate chromatin from the plant and examines it with
the electron microscope and see characteristic beads on a string structure. After addition of a small
amount of nuclease, which cleaves the string into individual beads that each contain 280 bp of DNA.
With more digestion a 120-bp fragment of DNA remains attached to a core of histone protein. Analysis
of the histone core reveals histones in the following proportions:
H2A 33.3%
H2B 33.3%
H3 0% [no histone H3 found]
H4 33.3%
Based on these observations, what conclusions can you make about the probable structure of
the nucleosome in the chromatin of this plant?
Be specific in describing the nature of the nucleosome: which histones form the core (),
how many of each are present () and size in bp of core-DNA that envelopes it ().
A previously undiscovered single celled organism was found living at a great depth on the ocean floor. Its nucleus contains only a single, linear chromosome consisting of 7x10^6 nucleotide pairs of DNA coalesced with three types of histone-like proteins. The analysis of individual nucleosomes revealed that each unit contained one copy of each protein and that the short linker DNA had no protein bound to it If the entire chromosome consists of nucleosomes (discounting any linker DNA), how many are there and how many total proteins are needed to form them?
Chapter 12 Solutions
Concepts of Genetics (12th Edition)
Ch. 12 - In bacteriophages and bacteria, the DNA is almost...Ch. 12 - After salivary gland cells from Drosophila are...Ch. 12 - If a human nucleus is 10 m in diameter, and it...Ch. 12 - Roberts syndrome is a rare inherited disorder...Ch. 12 - Prob. 2CSCh. 12 - Roberts syndrome is a rare inherited disorder...Ch. 12 - HOW DO WE KNOW? In this chapter, we focused on how...Ch. 12 - CONCEPT QUESTION Review the Chapter Concepts list...Ch. 12 - Contrast the size of the single chromosome in...Ch. 12 - Describe the structure of giant polytene...
Ch. 12 - What genetic process is occurring in a puff of a...Ch. 12 - During what genetic process are lampbrush...Ch. 12 - Why might we predict that the organization of...Ch. 12 - Describe the sequence of research findings that...Ch. 12 - Describe the molecular composition and arrangement...Ch. 12 - Describe the transitions that occur as nucleosomes...Ch. 12 - Provide a comprehensive definition of...Ch. 12 - Mammals contain a diploid genome consisting of at...Ch. 12 - Assume that a viral DNA molecule is a 50-m-long...Ch. 12 - How many base pairs are in a molecule of phage T2...Ch. 12 - Examples of histone modifications are acetylation...Ch. 12 - Contrast the structure of SINE and LINE DNA...Ch. 12 - Variable number tandem repeats (VNTRs) are...Ch. 12 - It has been shown that infectious agents such as...Ch. 12 - Cancer can be defined as an abnormal proliferation...Ch. 12 - In a study of Drosophila, two normally active...Ch. 12 - Prob. 21ESPCh. 12 - An article entitled Nucleosome Positioning at the...Ch. 12 - Prob. 23ESPCh. 12 - Following is a diagram of the general structure of...Ch. 12 - Microsatellites are currently exploited as markers...Ch. 12 - At the end of the short arm of human chromosome 16...
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- A previously undiscovered single-cell organism was found living at a great depth on the ocean floor. Its nucleus contained only a single linear chromosome with 7 x 106 nucleotide pairs of DNA coalesced with three types of histone-like proteins. Consider the following questions: Question: The analysis of individual nucleosomes reveals that each unit contained one copy of each protein and that the shortlinker DNA contained no protein bound to it. If the entirechromosome consists of nucleosomes (discounting any linkerDNA), how many are there, and how many total proteins areneeded to form them?arrow_forwardHuman Chromosome 22 (48 × 106 nucleotide pairs in length) has about 700 protein-coding genes, which average 19,000 nucleotide pairs in length and contain an average of 5.4 exons, each of which averages 266 nucleotide pairs. What fraction of the average protein-coding gene is converted into mRNA? What fraction of the chromosome do these genes occupy?arrow_forwardAssuming that the histone octamer forms a cylinder 9 nm in diameter and 5 nm in height and that the human genome forms 32 million nucleosomes, what volume of the nucleus (6 μm in diameter) is occupied by histone octamers?arrow_forward
- In Human chromosome 11 GC content is 42%. What is the percentage of each nucleotide on chromosome 11?arrow_forwardChromatin is differentiated into heterochromatin and euchromatin regions, on the basis of staining behaviour in a typical nucleus. Which of the given statements is/are correct w.r.t. heterochromatin? (A) Lightly stained region (B) Chromatin is densely packed (C) Transcriptionally it is inactive (D) Darkly stained region 1. (A) only 2. (A) and (C) only 3. (A), (B) and (C) 4. (B), (C) and (D)arrow_forwardassuming a spacing of approxiametly 200 base pairs per nucleosome, how many molecules of histone H4 are present in one somatic human cell?arrow_forward
- An old genetic observation is that a normally active gene will be silenced if it is moved by transposition or crossing over from an uncondensed (euchromatic) region to a heavily condensed (heterochromatic) region of a chromosome. Assume the euchromatic chromatin containing the active gene is surrounded by heterochromatic chromatin immediately after insertion. Please explain in terms of the control of histone modification why the normally active gene is silenced when it becomes surrounded by condensed regions. (Do not explain how histone modification causes chromatin condensation.)arrow_forwardAll of the following statements regarding nucleosomes are true EXCEPT A each bead-like structure contains 8 molecules of histones H1, H2A, H2B, H3 and H4 the bead like structures are made up of core histones wrapped around by the DNA strands the histone proteins in the nucleosomes contain positively charged amino acids that interact with the negatively charged DNA D the bead like structures are linked to each other by the DNA chainarrow_forwardwhat are we looking at in part (b)? Is this an11-nm fiber, a 30-nm fiber, or a 300-nm fiber? Does this DNAcome from a cell during M phase or interphase?arrow_forward
- There are 40 chromosomes in somatic cells of the house mouse. (a) How many chromosomes does a mouse receives from its father? (b) How many autosomes are present in a mouse gamete? (c) How many sex chromosomes are in a mouse ovum? (d) How many autosomes are in somatic cells of a female?arrow_forwardGive at least one example of a chromosomal structureor function affected by the following mechanisms formodulating chromatin structure:a. Posttranslational changes of the normal histonesfound in the nucleosomearrow_forwardIn a typical eukaryotic cell, would you expect to find more molecules of the H1 histone or more molecules of the H2A histone? Would you expect to find more molecules of H2A or more molecules of H3? Explain your reasoning.arrow_forward
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