Chapter 7, Problem 35P

Summary Introduction

To analyze:

Considering the results of DNA replication analysis of living microbe from Mars conclude about the mechanism of DNA replication in this organism.

Introduction:

Meselson and Stahl performed an experiment to identify the mechanism of DNA replication in any known or unknown organism. In this experiment, an organism that possessed double stranded DNA was allowed to grow on a medium containing ${}^{\text{15}}\text{N}$ (Heavy isotope of nitrogen); after that, they transferred the organism to a medium containing ${}^{\text{14}}\text{N}$ (Light isotope of nitrogen). When DNA is isolated from the experimental organism after 1 replication cycle and ${\text{C}}_{\text{s}}\text{Cl}$ ultracentrifugation followed by densitometry is performed, it shows intermediate density (${}^{\text{15}}\text{N}$ ${}^{\text{14}}\text{N}$) DNA. From this result, Meselson and Stahl concluded that the process of DNA replication is semi-conservative.