Modifications of histone tails can: affect expression of some genes in response to the environment. affect chromatin structure. activate transcription of some genes. repress transcription of some genes. all of these choices are correct.

All of these choices are correct.

Explanation:

Histone modification can be defined as a type of gene expression regulation. It refers to covalent post-translational modifications of histon tail proteins such as methylation, phosphorylation, acetylation, ubiquitylation, and sumoylation. As a consequence of modifications, chromatin structure might be changed, into active regions of euchromatin, (active transcription), or heterochromatin regions (inactive transcription).

Modification might be due to response to the environment, are heritable and are called epigenetic control.

answer: land bridge theory. land bridge theory held that shifting portions of dry land explained the finding of identical species on different continents. plate tectonic theory eventually eliminated the land bridge theory.

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times