science extended response

in 1859, charles darwin proposed his famous theory of evolution that explains how organisms slowly change over time. he, with alfred russel wallace, introduced the concept of natural selection, "survival of the fittest," according to which organisms with dominant traits are more likely to survive and reproduce.

six years later, austrian monk gregor mendel formulated his theory on particulate inheritance, the way genes pass traits on from one generation to the next, through his famous pea plant experiments. these genes control how the offspring looks, not a 'blending' of traits, as was previously thought by darwin. mendel’s results allowed him to develop the 3 laws of principles of inheritance.

the next year, ernst haeckel discovered that dna is located in the nucleus through his experiments.

thanks to haeckel’s discovery, friedrich miescher successfully isolated DNA from the cell nuclei in 1869. he proved that the nuclein (dna) is present in other cells as well, and identified DNA as a distinct molecule.

frederick griffith stated that a "transforming principle" enables the transfer of characteristics from one type of bacteria to another. he believed in 1928 that this “transforming principle” was a protein.

oswald avery, colin macleod and maclyn mccarty's research and experiments in 1944 established dna as the molecule in charge of inheritance, and that it can transform the properties of cells, clarifying the chemical nature of genes. they identified dna as the "transforming principle," proving griffith wrong.

in 1953, rosalind franklin's x-ray diffraction research and analyses helped her discover the double-helix structure of DNA. her finding was made possible by her creation of photo 51 and more recent developments in model building, which is the assembling of 3-d structures based on known chemical distances and bond angles. franklin’s discovery led to many other significant discoveries, making it the pathway to things such as biotechnology, dna replication and the polymerase chain reaction (PCR), one of the most important innovations in dna technology.

thanks to franklin’s amazing discovery, fredrick sanger was able to create the first dna sequencing technique in 1977, called the "chain termination method.” he discovered ways to arrange the amino acids, making him the first person to acquire a protein sequence. he did this by demonstrating that proteins are ordered molecules, and the genes and DNA that produce these proteins must have a sequence. he also employed his technique to sequence the bacteriophage PhiX174, the first genome ever.