Nuclei have been isolated from a stem cell line at 0, 1, 2, and 4 days after the
ID: 214911 • Letter: N
Question
Nuclei have been isolated from a stem cell line at 0, 1, 2, and 4 days after the cell line has been induced to differentiate into muscle type cells. The nuclei are subjected to digestion with DNase, the DNA is then extracted from the nuclei and cleaved with a restriction enzyme that cleaves the DNA external to genes X and Y. The digestion products are run on a gel and analyzed by Southern blots using a labeled probe that binds to either X or Y DNA (or RNA). The results of this experiment are shown on the Southern blot below at the left. The experiment is repeated, but without DNase, and the results are shown on the Southern blot below in the middle. Finally, RNA, extracted from the cells at days 0, 1, 2 and 4 after induction, is run on gels which are then blotted and probed for the presence of X or Y RNA, as shown in the Northern blot below, right.
What is a likely explanation why the pattern of bands on the Southern blot at the left differs from the pattern on the Northern blot?
Days of induction01 2 4 0 1 24 Probe X Probe Y | Southern blot Southern blot Northern blotExplanation / Answer
DNase will cleave the DNA at sites where DNA is accessible ( free from histones) . Acetylation of histones repels the DNA making it accessible. This is because acetyl group is negative and phosphate group in DNA is also negative. So, these regions are transcriptionally active. All in all,those regions which are cleaved by the DNase( faint band in southern blot) are transcriptionally active ( dark bands in northern blot).
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.