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.

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.

Watson and Crick crystallized DNA to be able to visualize the structure, and it was this finding that led them to propose the double helix. Fun fact: Rosalind Franklin's work was essential to this finding as she was the expert in x-ray crystallography, but Watson and Crick are traditionally given all the credit.

It was Gregor Mendel who did studies on pea plants to first described the concepts behind genetic inheritance. By breeding pea plants with different visible phenotypes and observing the phenotypes of the offspring produced, he was the first scientist to provide rules for heredity (now known as Mendelian inheritance).

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.

Polymerase chain reaction (PCR) is a method by which a specific sequence of DNA can be copied and replicated many times over in a test tube, which has been of enormous importance to the field of molecular biology. The other techniques listed all are important in molecular biology as well, but are typically for detection or other manipulations, not replication.

There are two primary factors that influence the quality of a polymerase chain reaction (PCR) primer. The first is length. The primer should ideally be roughly 18-30 bases in length; this qualification can be used to rule out two of the possible given answer options. The second factor is the melting point of the primer. An ideal oligonucleutide sequence will have a relatively high cytosine/guanine content. These particular bases form three hydrogen bonds in the DNA molecule, while adenine and thymine form only two. Cytosine and guanine interactions thus require more energy to break, and raise hte melting point of the sample. The process of PCR requires heating the sample at certain points, which can become a problem for primers with high adenine/thymine content.

Our ideal answer will be a longer sequence (18 bases) with a high percentage of cytosine and guanine residues.

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 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.

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.