¿En genética a qué hace referencia el concepto de "histones tails"?
Histone tails are responsible for the expansion and contraction of DNA. If you look at diagrams of mitosis and meiosis, you can see how the chromatin expands and contracts. During the replication stage, the DNA is completely unwound (giving the nucleus a clear appearance) allowing rRNA to do it´s job.
The tails bond covalently, I don´t remember if it´s to DNA or to other histones, but these bonds wind up the DNA to give it the X or Y appearance as seen under the microscope.
You shouldn´t need to know more than that in an intro class.
Histone tails are portions of histone proteins that, with the activity of other corepressors/coactivators, help to regulate the expression of DNA (Transcription). There is also evidence to suggest that the N-terminal tails aid in the formation of 30-nm chromatin fibers.
During the replication stage, the DNA is completely unwound (giving the nucleus a clear appearance) allowing rRNA to do it´s job.
This information is partially incorrect (I have studied molecular biology for the past 5 years). rRNA does not have anything to do with DNA replication. I think what you may be thinking of is translation and not replication (although, histones do have a role in the regulation of DNA replication).
Different modifications of different positions of the N-terminal tail have been linked to various results. For example, here is short a list of some of the effects known to occur as a result of histone tail modifications:
1). Unmodified - possible gene silencing
2). acetylated (position dependent) - gene expression, histone deposition
3). phosphorylated (position dependent) - mitosis/meiosis (replication)
4). methylation - gene silencing
If you are interested. Here are a few helpful animation of DNA replication that are easy to watch and understand. I always find that visualizations are a good aid to understanding concepts such as these:
Read this article until you get to where they start discussing N-terminal tails then research from there.
Siento que el artículo es en inglés. ![n-terminal tails]
The assembly of higher order chromatin structures has been linked to the covalent modifications of histone tails
Es lo único que he podido encontrar. No sé si alguien lo puede explicar.