cally more complicated version of what had been discovered in bacteria. However, this view has changed dramatically as biologists have considered the effect of the organization of genomic DNA in eukaryotes. Compared with eukaryotic DNA, bacterial DNA is relatively “naked," making it readily accessible to RNA polymerase. In contrast, eukaryotic chromosomes are packaged into chromatin, which is composed of DNA and proteins (mostly his- tones). The basic unit of chromatin is the nucleosome, which contains -150 bp of DNA wrapped 1.7 times around a core of histone proteins (Figure 12-11). The nucleosome core contains eight histones, two subunits of each of the four histones: histones 2A, 2B, 3, and 4 (called H2A, H2B, H3, and H4) organized as two dimers of H2A and H2B and a tetramer of H3 and H4. Surrounding the nucleosome core is a linker histone, H1, which can compact the nucleosomes into higher-order struc- tures that further condense the DNA. FIGURE 12-11 (a) The nucleosome in decondensed and condensed chromatin. (b) End view of the coiled chain of nucleosomes. (c) Chromatin structure varies along the length of a chromosome. The least-condensed chromatin (euchromatin) is shown in yellow, regions of intermediate condensation are in orange and blue, and heterochromatin coated with special proteins (purple) is in red. [c) Fram P. J. Hom and C. L. Peterson, "Chromatin Higher Order Folding: Wrapping Up Transcription," Science 297, 2002, 1827, Fig. 3. Copyright 2002, AAAS.] The structure of chromatin (a) Short region of DNA double helix 2 nm Nucleosomes: the basic unit 11 nm of chromatin Chromatin fiber of packed nucleosomes 30 nm 10 nm DNA wrapped around histone (b) H1 histone core DNA Octameric histone core Histone octamer Н2А, Н2В, Нз, НА `H1 histone Nucleosome (c) 30 nm
cally more complicated version of what had been discovered in bacteria. However, this view has changed dramatically as biologists have considered the effect of the organization of genomic DNA in eukaryotes. Compared with eukaryotic DNA, bacterial DNA is relatively “naked," making it readily accessible to RNA polymerase. In contrast, eukaryotic chromosomes are packaged into chromatin, which is composed of DNA and proteins (mostly his- tones). The basic unit of chromatin is the nucleosome, which contains -150 bp of DNA wrapped 1.7 times around a core of histone proteins (Figure 12-11). The nucleosome core contains eight histones, two subunits of each of the four histones: histones 2A, 2B, 3, and 4 (called H2A, H2B, H3, and H4) organized as two dimers of H2A and H2B and a tetramer of H3 and H4. Surrounding the nucleosome core is a linker histone, H1, which can compact the nucleosomes into higher-order struc- tures that further condense the DNA. FIGURE 12-11 (a) The nucleosome in decondensed and condensed chromatin. (b) End view of the coiled chain of nucleosomes. (c) Chromatin structure varies along the length of a chromosome. The least-condensed chromatin (euchromatin) is shown in yellow, regions of intermediate condensation are in orange and blue, and heterochromatin coated with special proteins (purple) is in red. [c) Fram P. J. Hom and C. L. Peterson, "Chromatin Higher Order Folding: Wrapping Up Transcription," Science 297, 2002, 1827, Fig. 3. Copyright 2002, AAAS.] The structure of chromatin (a) Short region of DNA double helix 2 nm Nucleosomes: the basic unit 11 nm of chromatin Chromatin fiber of packed nucleosomes 30 nm 10 nm DNA wrapped around histone (b) H1 histone core DNA Octameric histone core Histone octamer Н2А, Н2В, Нз, НА `H1 histone Nucleosome (c) 30 nm
Biochemistry
6th Edition
ISBN:9781305577206
Author:Reginald H. Garrett, Charles M. Grisham
Publisher:Reginald H. Garrett, Charles M. Grisham
Chapter28: Dna Metabolism: Replication, Recombination, And Repair
Section: Chapter Questions
Problem 1P: Semiconservative or Conservative DNA Replication If 15N-Iabeled E. coli DNA has a density of 1.724...
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Question
In Figure 12-11b, in what chromosomal region are you
likely to find the most H1 histone protein?
![cally more complicated version of what had been discovered in bacteria. However,
this view has changed dramatically as biologists have considered the effect of the
organization of genomic DNA in eukaryotes.
Compared with eukaryotic DNA, bacterial DNA is relatively “naked," making it
readily accessible to RNA polymerase. In contrast, eukaryotic chromosomes are
packaged into chromatin, which is composed of DNA and proteins (mostly his-
tones). The basic unit of chromatin is the nucleosome, which contains -150 bp of
DNA wrapped 1.7 times around a core of histone proteins (Figure 12-11). The
nucleosome core contains eight histones, two subunits of each of the four histones:
histones 2A, 2B, 3, and 4 (called H2A, H2B, H3, and H4) organized as two dimers of
H2A and H2B and a tetramer of H3 and H4. Surrounding the nucleosome core is a
linker histone, H1, which can compact the nucleosomes into higher-order struc-
tures that further condense the DNA.
FIGURE 12-11 (a) The nucleosome in
decondensed and condensed chromatin.
(b) End view of the coiled chain of
nucleosomes. (c) Chromatin structure
varies along the length of a chromosome.
The least-condensed chromatin
(euchromatin) is shown in yellow, regions
of intermediate condensation are in orange
and blue, and heterochromatin coated
with special proteins (purple) is in red.
[c) Fram P. J. Hom and C. L. Peterson,
"Chromatin Higher Order Folding: Wrapping
Up Transcription," Science 297, 2002, 1827,
Fig. 3. Copyright 2002, AAAS.]
The structure of chromatin
(a)
Short region of
DNA double helix
2 nm
Nucleosomes:
the basic unit
11 nm
of chromatin
Chromatin fiber
of packed
nucleosomes
30 nm
10 nm
DNA wrapped
around histone
(b)
H1 histone
core
DNA
Octameric
histone core
Histone
octamer
Н2А, Н2В,
Нз, НА
`H1 histone
Nucleosome
(c)
30 nm](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1738475d-5a75-432a-8c02-4bd258efa05c%2Ffb9c5d40-f43e-4afc-b2be-ab09b8d1bb6b%2Fry78e6h_processed.png&w=3840&q=75)
Transcribed Image Text:cally more complicated version of what had been discovered in bacteria. However,
this view has changed dramatically as biologists have considered the effect of the
organization of genomic DNA in eukaryotes.
Compared with eukaryotic DNA, bacterial DNA is relatively “naked," making it
readily accessible to RNA polymerase. In contrast, eukaryotic chromosomes are
packaged into chromatin, which is composed of DNA and proteins (mostly his-
tones). The basic unit of chromatin is the nucleosome, which contains -150 bp of
DNA wrapped 1.7 times around a core of histone proteins (Figure 12-11). The
nucleosome core contains eight histones, two subunits of each of the four histones:
histones 2A, 2B, 3, and 4 (called H2A, H2B, H3, and H4) organized as two dimers of
H2A and H2B and a tetramer of H3 and H4. Surrounding the nucleosome core is a
linker histone, H1, which can compact the nucleosomes into higher-order struc-
tures that further condense the DNA.
FIGURE 12-11 (a) The nucleosome in
decondensed and condensed chromatin.
(b) End view of the coiled chain of
nucleosomes. (c) Chromatin structure
varies along the length of a chromosome.
The least-condensed chromatin
(euchromatin) is shown in yellow, regions
of intermediate condensation are in orange
and blue, and heterochromatin coated
with special proteins (purple) is in red.
[c) Fram P. J. Hom and C. L. Peterson,
"Chromatin Higher Order Folding: Wrapping
Up Transcription," Science 297, 2002, 1827,
Fig. 3. Copyright 2002, AAAS.]
The structure of chromatin
(a)
Short region of
DNA double helix
2 nm
Nucleosomes:
the basic unit
11 nm
of chromatin
Chromatin fiber
of packed
nucleosomes
30 nm
10 nm
DNA wrapped
around histone
(b)
H1 histone
core
DNA
Octameric
histone core
Histone
octamer
Н2А, Н2В,
Нз, НА
`H1 histone
Nucleosome
(c)
30 nm
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