Once DNA was shown to be the primary genetic material of life, a race among scientists took place to work out its structure. Which concept came from studying the amounts of each DNA base in different organisms?

The discovery of deoxyribonucleic acid (DNA) forever changed the understanding of genetics, the study of how physical and physiological inheritance is passed down from generation to generation.

The DNA molecule was first identified in the second half of the 19th century. A century later, in the middle of the 20th century, the golden age of discoveries in genetics began, when the structure and functioning of the genetic code was defined.

Today, scientists are focused on researching how to edit DNA to correct mistakes and cure diseases of genetic origin.

DNA was first isolated in 1869 by the Swiss biologist Johan Friedrich Miescher. While studying the chemical composition of white blood cells, he observed that within the cells there was an isolated substance rich in phosphates, without sulfur and resistant to proteases, something that did not correspond to the typical structure of lipids or proteins.

Miescher baptized that new molecule as nuclein, since it was found in the nucleus of all the cells studied.

Between 1885 and 1901, the chemical composition of DNA began to be defined. In 1889 Richard Altmann, a German pathologist who had been a disciple of Miescher, redefined this substance with the term "nucleic acid".

For his part, the German doctor Albert Kossel discovered the existence of carbohydrates and some compounds or nitrogenous bases which he called "adenine", "guanine", "cytosine" and "thymine" within the DNA molecule. This discovery earned him the Nobel Prize for Medicine in 1910. The 20th century began with great advances in DNA research. During the 1920s, Russian-American biochemist Phoebus Levene determined the existence of RNA, another nucleic acid necessary for the transmission of genetic information.

Levene also detected the presence of phosphate group and a type of sugar called ribose, two essential components in the formation of DNA. Later, the biochemist discovered that the phosphate group, sugar, and nitrogenous bases bound together to form nucleotides.

Once the shape and composition of DNA has been discovered, the latest studies focus on how it works: seeing what chemical reactions take place inside the cell in order to try to reproduce them in the laboratory.

Explanation:

In this way, genetic editing techniques aim to modify the genetic code of some cells whose DNA is incorrect or damaged, which can cause disorders and diseases.

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.