Hershey and Chase used radioisotopes to trace the DNA of a T2 phage (a virus that infects E. coli). Proteins contain sulfur; DNA does not. DNA contains phosphate; proteins do not. Using radioactive forms of sulfur and phosphate, they were able to selectively incorporate these isotopes into either the DNA or protein of a T2 phage and then physically separated the infected and uninfected bacteria. They found that the sulfur was not incorporated, while a portion of the phosphate entered the cells and could be recovered in the next generation. From these results, they were able to conclude that protein was not a hereditary material.

Miescher, a Swiss chemist, first identified "nuclein" in the nuclei of white blood cells. He noted that the substance contained higher levels of phosphorus than other proteins and was resistant to proteolysis. This discovery was not widely appreciated for over 50 years.

DNA microarray allows investigators to analyze gene expression on a large scale. A Northern blot only permits analysis of the expression of one (or several) genes at a time. PCR is a method of amplifying DNA and a Western blot allows for analysis of proteins.

The dispersive model (now recognized to be incorrect), proposed that every occurrence of DNA replication would create DNA hybrids (from fragments of the the original double helix) that are one part original and one part new DNA. Each additional round would produce double helices with greater and greater quantities of DNA.

Levene accomplished all of these. He published more than 700 papers during his career. He used hydrolysis to break down and analyze yeast nucleic acids, proposing the composition of nucleic acids (phosphate, sugar, base) in 1919.

One strain of Pneumococcus was called smooth due to a protective capsule, and the other strain that lacked the capsule was called rough. Mice that were injected with the smooth strain died, and mice injected with the rough strain lived because their immune system killed the bacteria. Griffith also killed some of the smooth strain and found that when mice were injected with the dead smooth strain lived, but mice injected with both live rough strain and dead smooth strain died. He determined that the living smooth strain cells were being transformed by some material from the dead smooth strain. Later experiments proved this material to be DNA.

The question is asking about separating mRNA fragments, not DNA fragments. Hence, the only procedure applicable is Northern blot. Southern blot is used for DNA, and Western blot is used for protein. In addition, there is no such thing as an Eastern blot.

The experiment performed by Hershey and Chase showed that bacteriophages insert their DNA into bacteria, and not their protein. This demonstrated that DNA is the genetic material, and not proteins. Law of independent assortment and segregation are both Mendelian concepts. 

Gregor Mendel was a German friar who lived in the mid- to late-nineteenth century. He conducted a years-long series of experiments using pea plants in which he carefully tracked each plant's physical traits and determined how cross-fertilization (breeding the pea plant to another pea plant, rather than to itself) affected the plants' offspring. Seed color, flower shape, height, and pod shape were among the traits he studied. In the end, he summarized his work into three laws of heredity: the laws of segregation, independent assortment, and dominance. He also coined the terms "recessive" and "dominant," in reference to genetic traits.

Unfortunately, Mendel's work remained largely unacknowledged through his life. The importance of his studies was only recognized by other scientists decades after his death.

Speciation is the event that occurs when two populations of a particular species can no longer interbreed. Speciation is not defined by physical barriers or by the time that two populations are separate from one another. In fact, two populations of the same species can be apart any distance or time, and if they can still interbreed they are considered the same species even if they look completely different.

Note that carrying capacity refers to the maximum number of individuals in a population that the natural resources of the surrounding environment can support. It is, essentially, the maximum healthy population size, and is not a measure of distance as implied in the answer choice.