Question

1-what seniconsevative replication is and how it was discovered to be the corrext model DNA replication.

2-List the eays tgat chromatin remodeling xomplexes can remodel de DNA and what are their functions?

3-how interphase chrimarin isnorganized in the nucleous and how it is condensed to regulate expression.

Answer 1

1)The semiconservative mode of DNA replication is that each of the new daughter strand has one parental and newly synthesised DNA.Here parental strand acts as a template for daughter strand

This was experimentally proved by Meselson and Stahl experiment in which  the E coli cell were incubated with heavy N15 medium for many generation leading to the integration of heavy isotope of nitrogen into the  DNA.

Later there was change in the medium from N15 to N14 (normal isotope ) and cells were recovered after fixed interval of time and were checked in cesium chloride density gradient.

The cells were shown to have the intermediate density as this contained both N15 and N14 isotope.(heavy nitrogen would settle at the bottom and light nitrogen would stay at the top).

After second interval of time there were both the intermediate and low density bands obtained in the sample in the same proportion which clearly indicated the semiconservative nature of DNA replication.As these results can only be obtained if the nature of DNA replication is semiconservative.

With the increased incubation there were more light nitrogen incubated and the proportion of  heavy nitrogen decreases which disapproves the conservative method of DNA replication.