BCMB 412 EXAM 2 QUESTIONS WITH
ANSWERS 100% CORRECT
beads on a string - ANSWER 10 nm fiber; euchromatin
micrococcal nuclease - ANSWER digests DNA reveals chromatin fibers are made of
DNA and protein; first digests the most accessible DNA (the string, or linker DNA)
histones - ANSWER primary proteins in mediating DNA folding into chromatin and are
the protein components of the nucleosome; high content of positively charged amino
acids
linker histones - ANSWER H1 and H5
core histones - ANSWER H2A, H2B, H3, H4; share a common structural fold; show
remarkable sequence conservation
nucleosomes - ANSWER DNA coiled around histones; functions as a barrier that
prevents proteins from binding DNA
nucleosome formation - ANSWER In solutions of moderate salt and in the absence of
DNA, the H3-H4 complex forms a tetramer; H2A-H2B form a stable dimer also in
moderate salt concentrations and no DNA. In the absence of DNA a tetramer of H3-H4
and two H2A-H2B dimers associate together to form the histone octamer. In the
presence of DNA, a H3-H4 tetramer, DNA and two H2A-H2B dimers spontaneously
associate sequentially to form the nucleosome
histone tails - ANSWER not required to maintain the structure of the nucleosome;
N-terminal tails stabilize the 30-nm fiber
indirect end labeling - ANSWER A technique for examining the organization of DNA by
, making a cut at a specific site and identifying all fragments containing the sequence
adjacent to one side of the cut; it reveals the distance from the cut to the next break(s) in
DNA
nucleosome positioning - ANSWER The placement of nucleosomes at defined
sequences of DNA instead of at random locations with regard to sequence; may be
promoted by certain proteins interacting with nucleosomes
DNA histone interactions - ANSWER induces DNA bending but are non-sequence
specific; majority of contacts are mediated by hydrogen bonds between histones and
DNA; between protein and oxygen atoms near the minor groove of the DNA; positive
charge of the histones facilitate the bending of the DNA
DNA sequences - ANSWER may act as nucleosome positioning signals; AT-rich DNA
tends to bend DNA toward the minor groove. Nucleosomal DNA is bent. Thus, AT-rich
DNA favor the formation of nucleosomes.
H1 - ANSWER histone that leads to more compaction of nucleosomal DNA; stabilizes the
nucleosome and promotes the 30 nm fiber by binding linker DNA
solenoid - ANSWER the linker DNA never passes through the axis of the fiber. It goes
around in circle.
zigzag - ANSWER the linker DNA goes through the axis and makes a spring like fiber.
chromatin loops - ANSWER mediates higher order chromatin structure; bases of the
loops are attached to a Nuclear scaffold - a proteinacious body.
nuclear scaffold - ANSWER Two classes of proteins have been identified in the scaffold.
These are Topo II and SMC proteins (Structural Maintenance of Chromosomes).
RNA Pol I - ANSWER transcribes rRNA
ANSWERS 100% CORRECT
beads on a string - ANSWER 10 nm fiber; euchromatin
micrococcal nuclease - ANSWER digests DNA reveals chromatin fibers are made of
DNA and protein; first digests the most accessible DNA (the string, or linker DNA)
histones - ANSWER primary proteins in mediating DNA folding into chromatin and are
the protein components of the nucleosome; high content of positively charged amino
acids
linker histones - ANSWER H1 and H5
core histones - ANSWER H2A, H2B, H3, H4; share a common structural fold; show
remarkable sequence conservation
nucleosomes - ANSWER DNA coiled around histones; functions as a barrier that
prevents proteins from binding DNA
nucleosome formation - ANSWER In solutions of moderate salt and in the absence of
DNA, the H3-H4 complex forms a tetramer; H2A-H2B form a stable dimer also in
moderate salt concentrations and no DNA. In the absence of DNA a tetramer of H3-H4
and two H2A-H2B dimers associate together to form the histone octamer. In the
presence of DNA, a H3-H4 tetramer, DNA and two H2A-H2B dimers spontaneously
associate sequentially to form the nucleosome
histone tails - ANSWER not required to maintain the structure of the nucleosome;
N-terminal tails stabilize the 30-nm fiber
indirect end labeling - ANSWER A technique for examining the organization of DNA by
, making a cut at a specific site and identifying all fragments containing the sequence
adjacent to one side of the cut; it reveals the distance from the cut to the next break(s) in
DNA
nucleosome positioning - ANSWER The placement of nucleosomes at defined
sequences of DNA instead of at random locations with regard to sequence; may be
promoted by certain proteins interacting with nucleosomes
DNA histone interactions - ANSWER induces DNA bending but are non-sequence
specific; majority of contacts are mediated by hydrogen bonds between histones and
DNA; between protein and oxygen atoms near the minor groove of the DNA; positive
charge of the histones facilitate the bending of the DNA
DNA sequences - ANSWER may act as nucleosome positioning signals; AT-rich DNA
tends to bend DNA toward the minor groove. Nucleosomal DNA is bent. Thus, AT-rich
DNA favor the formation of nucleosomes.
H1 - ANSWER histone that leads to more compaction of nucleosomal DNA; stabilizes the
nucleosome and promotes the 30 nm fiber by binding linker DNA
solenoid - ANSWER the linker DNA never passes through the axis of the fiber. It goes
around in circle.
zigzag - ANSWER the linker DNA goes through the axis and makes a spring like fiber.
chromatin loops - ANSWER mediates higher order chromatin structure; bases of the
loops are attached to a Nuclear scaffold - a proteinacious body.
nuclear scaffold - ANSWER Two classes of proteins have been identified in the scaffold.
These are Topo II and SMC proteins (Structural Maintenance of Chromosomes).
RNA Pol I - ANSWER transcribes rRNA
