By Rene Fester Kratz

Get ready to dive in to ten of the most important biology discoveries to date. These are listed in no particular order because they’ve all made a significant impact on the advancement of biology as a science and increased what people know and understand about the living world.

Seeing the unseen

Before 1675, people believed the only living things that existed were the ones they could see. That year, a Dutch cloth merchant named Antony van Leeuwenhoek discovered the microbial world by peering through a homemade microscope. Van Leeuwenhoek was the first person to see bacteria, which he described as little animals that moved about here, there, and everywhere. His discovery of a previously unseen universe not only turned people’s worldviews inside out but also laid the foundation for the understanding that microbes cause disease.

Discovering penicillin, the first antibiotic

People had very few tools to combat bacterial infections until Alexander Fleming discovered the antibacterial properties of penicillin in 1928. Fleming was studying a strain of staphylococcus bacteria when some of his petri dishes became contaminated with Penicillium mold. To Fleming’s surprise, wherever the Penicillium grew on the petri dish, the mold inhibited the growth of the staphylococcus bacteria.

The compound penicillin was purified from the mold and first used to treat infections in soldiers during World War II. Soon after the war, the “miracle drug” was used to treat infections in the general public, and the race to discover additional antibiotics was on.

Protecting people from smallpox

Would you believe that the idea of inoculating people against diseases such as smallpox, measles, and mumps originated in ancient China? Healers there ground up scabs taken from a smallpox survivor into a powder and blew this dust into the nostrils of their patients. Gross as this may sound, these ancient healers were actually inoculating their patients to help prevent the spread of the disease.

This practice laid the foundation for the later work of Dr. Edward Jenner, who developed the first vaccine against smallpox, in 1796. The smallpox vaccine was so effective that doctors were able to totally eradicate this disease from the human population. Imagine that: a disease that killed millions of people completely gone. (And now, using the same strategy, we’re very close to eradicating polio!)

Defining DNA structure

James Watson and Francis Crick figured out how a code could be captured in the structure of DNA molecules, opening the door to an understanding of how DNA carries the blueprints for proteins. They proposed that DNA is made of two nucleotide chains running in opposite directions and held together by hydrogen bonds between the nitrogenous bases. Using metal plates to represent the bases, they built a giant model of DNA that was accepted as correct almost immediately.

Finding and fighting defective genes

On August 24, 1989, scientists announced their discovery of the first known cause of a genetic disease: They found a tiny deletion from a gene on Chromosome 7 that resulted in the deadly genetic disease cystic fibrosis. This identification of a genetic defect, and the realization that this defect causes a disease, opened the floodgates of genetic research

Since that fateful day, the genes for other diseases, such as Huntington’s disease, inherited forms of breast cancer, sickle cell anemia, Down syndrome, Tay-Sachs disease, hemophilia, and muscular dystrophy, have been found. Genetic tests for these diseases are available to detect whether an unborn baby has a defective gene or whether two potential parents would likely produce an affected baby. And knowing what causes the diseases enables researchers to focus on ways to possibly cure the diseases.

Discovering modern genetic principles

Gregor Mendel, a mid-19th century Austrian monk, used pea plants to perform the fundamental studies of heredity that serve as the basis for genetic concepts to this day. Because pea plants have a number of readily observable traits — smooth peas versus wrinkled peas, tall plants versus short plants, and so on — Mendel was able to observe the results of cross-pollinating and growing various varieties of pea plants.

Through his experiments, Mendel was able to establish that genetic factors are passed from parents to offspring and remain unchanged in the offspring so that they can be passed on again to the next generation. Although his work was done before the discovery of DNA and chromosomes, the genetic principles of dominance, segregation, and independent assortment that Mendel originally defined are still used to this day.

Evolving the theory of natural selection

Charles Darwin’s study of giant tortoises and finches on the Galapagos Islands led to his famous theory of natural selection (also known as “survival of the fittest”), which he published in his 1859 book titled On the Origin of Species. The main point of Darwin’s theory is that organisms with traits that are better suited to the conditions in which they live are more likely to survive and reproduce, passing on their traits to future generations.

These better-suited variations tend to thrive in the given area, whereas less-suited variations of the same species either don’t do as well or just die off. Thus, over time, the traits seen in a population of organisms in a given area can change. The importance of Darwin’s theory of natural selection can be seen today in the evolution of antibiotic-resistant strains of bacteria.

Formulating cell theory

In 1839, zoologist Theodor Schwann and botanist Matthias Schleiden were talking at a dinner party about their research. As Schleiden described the plant cells he’d been studying, Schwann was struck by their similarity to animal cells. The similarity between the two types of cells led to the formation of cell theory, which consists of three main ideas:

  • All living things are made of cells.
  • The cell is the smallest unit of living things.
  • All cells come from preexisting cells.

Amplifying DNA with PCR

In 1983, Kary Mullis discovered the polymerase chain reaction (PCR), a process that allows scientists to make numerous copies of DNA molecules that they can then study. Today, PCR is used for

  • Making lots of DNA for sequencing
  • Finding and analyzing DNA from very small samples for use in forensics
  • Detecting the presence of disease-causing microbes in human samples
  • Producing numerous copies of genes for genetic engineering

Editing DNA with CRISPR

French microbiologist Emmanuelle Charpentier was intrigued by a strangely repetitive piece of DNA called CRISPR that bacteria use to defend themselves against viruses. Her work led to a breakthrough in how molecules of RNA inside the bacterium Streptococcus pyogenes interacted with this piece of DNA. Then, Charpentier teamed up with American biologist Jennifer Doudna and the two scientists figured out how the RNA, DNA, and a protein called cas9 work to create a very targeted gene-editing system in the bacteria.

The bacteria use this gene-editing system to keep a copy of viral DNA codes so they can defend themselves against future encounters with viruses. That’s very cool, but the real reason this discovery makes this list is because scientists all over the world are now exploring how they can use this bacterial gene-editing system to edit the genes of other species.

The possibilities are vast (and some are scary), but a major hope is that scientists will be able to use this system to treat genetic diseases by replacing defective genes with normal ones. Although this discovery is very recent, we’re sure that we’ll be hearing lots more about CRISPR in the future.