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.

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). 

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. 

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. 

This process is known as transformation. It was discovered after Griffith heat treated bacteria (to destroy their virulence) and noticed that mice injected with the heat-killed bacteria and a living, non-virulent strain would die of infection.

In 1910, Thomas Hunt Morgan performed a test cross between white-eyed male Drosophila and homozygous red-eyed females to test the frequency of white eyes in the subsequent generations. The F1 generation all had red eyes, but when Morgan crossed the F1 generation, he noticed a 3:1 ratio of red to white eyes in the F2 generation. In all of his experimements, the white-eyed F2 flies were always male. Subsequent experiments supported the hypothesis that the white-eye trait was sex-linked (in this case, to the X chromosome).

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.