In order to allow gene expression, histone modifying enzymes interact with core histones to modulate their affinity for the DNA and/or other histones, so that specific sequences can be exposed to allow for transcription. From the list below, choose all of the statements that are true.

A) the 'tails' of core histones are an important site for covalent modifications by histone modifying enzymes
B) Histones can be modified in a variety of ways, including methylation, acetylation and phosphorylation.
C) Histones modifications are binary, meaning that modifcations will turn the histone 'on' or 'off'.
D) Histone modifying enzymes can slide the core histones along the DNA without removing it.
E) The H1 histone is sometimes removed, to help expose the DNA for transcription

A, B, C and D are correct

Explanation:

The statement E is not correct because the Histone H1 does not form the histone octamer that is associated with DNA to form the nucleosomes. The histones in the nucleosome are H2A, H2B, H3 and H4.

The function of H1 is to act as a linker between nucleosomes in the chromatin fiber.

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answer: b. nucleolus

explanation: nucleolus is a structure in the nucleus are ribosomes are made.

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: d

-charlie

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: d

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.