Question

Eukaryotic gene regulation: Epigenetic factors

Chromatin structure: histones, methylation; euchromatin vs. heterochromatin. How does all this affect transcription?

X chromosome inactivation. Why does it happen? How does it happen? How does it result in calico cats? What does Xist do?

Heritable, but can be modified by environment… what does this mean?

Prader-Willi syndrome vs. Angelman syndrome: compare and contrast.

microRNAs. How are they different from mRNAs? How do they interact with mRNAs? How are microRNAs different from Xist or other long noncoding RNAs?

Answer 1

1) histones are proteins that bind to the DNA and help to form a compact structure. Methylation either on the DNA or on the histones mask the negative charges on them (due to phosphate on the former and acidic r studies on the latter) causing their interaction to become more strong and compact. Now if a segment of DNA is tightly bound to the histones it will be difficult for it to unwind in order to facilitate transcription. Such a region is called heterochromatin. If a region of DNA is loosely interacting with the histones then it can be easily opened to allow transcription and is called as euchromatin.