Notes

(1933)
- The first prototype of the electron microscope was constructed. A type of microscope which utilizes a beam of electrons to create an image of the specimen

Erwin Chargaff(1943)
- A scientist named began to challenge Levene's previous conclusions.
(1950)
- Noted that the nucleotide composition of DNA differs among species and do not repeat in the same order reaches two major conclusions.

Chargaff concluded that almost all DNA, no matter what organism or tissue type it comes from, still maintains certain properties, even as its composition varies. He postulated the "Chargaff's Rule" which says that the amount of cytosine is equal to the amount of guanine, and the amount of adenine. In short, the total amount of pyrimidines (thymine and cytosine) approximates the amount of purines (adenine and guanine).

George Grey(1951)
- Meanwhile in the field of cytology, George Grey has successfully made the first continuous cell line to be cultured. The cell line was derived from the cervical cancer cells of Henrietta Lacks, thus these cells were referred to as HeLa cells. These cells played a significant role in the course of cell biology.

James Watson and Francis Crick (1953)
- They derived the three-dimensional and double helical model of the DNA (Pray 2009). After that, the process of replicating the DNA was discovered.

(1970)
- Reverse transcriptase in retroviruses was first discovered.

(1977)
- Frederick Sanger introduced the process of DNA sequencing. The first ever organism to have its genome sequence is a bacteriophage.