Question

Which statements about the modification of chromatin structure in eukaryotes are true? Select all that apply. View Available Hint(s) Select all that apply. Deacetylation of histone tails in chromatin loosens the association between nucleosomes and DNA. Methylation of histone tails in chromatin can promote condensation of the chromatin. DNA is not transcribed when chromatin is packaged tightly in a condensed form. Acetylation of histone tails is a reversible process. Some forms of chromatin modification can be passed on to future generations of cells. Acetylation of histone tails in chromatin allows access to DNA for transcription.

Answer 1

The correct answers are:  

• Methylation of histone tails in chromatin can promote condensation of the chromatin.

• DNA is not transcribed when chromatin is packaged tightly in a condensed form.

• Acetylation of histone tails is a reversible process.

• Some forms of chromatin modification can be passed on to future generations of cells.  

• Acetylation of histone tails in chromatin allows access to DNA for transcription.

Histone modifications are post-translational modifications of histone protein that can affect gene expression by altering chromatin structure or recruiting histone modifiers.The most common modifications are methylation, phosphorylation, acetylation and ubiquitylation. All of them affect the binding affinity between histones and DNA and thus loosening (gene activation) or tightening (gene repression) the condensed DNA.

Histone methylation is a transfer of methyl group by histone methyltransferases to lysine or arginine amino acid of protein. Effect of methylation depends on the type of protein that is modified. Demethylation is the reverse process.

Histone acetylation is the process of adding of an acetyl group(by  histone acetyltransferases) to histone proteins and it can also activate or inhibit the gene expression. Deacetilation is reverse process.