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What is Molecular Biology? History, Core Concepts, & Applications

Molecular biology is the branch of biology dealing with the molecular basis of all living things—the study of macromolecules, such as proteins and DNA, and the mechanisms behind the way they interact within cells. 

It’s a field of the life sciences with a rich history that has massively impacted disease prevention, diagnosis, and treatment as techniques have continued to improve, helping scientists and clinicians better understand the structures and functions within individual cells. 

With this increased knowledge, we are able to answer not only basic scientific questions, but also more complex questions about physiology, the immune system, and diseases in humans.

A Brief History of Molecular Biology 

Molecular biology emerged as an answer to the nature of inheritance among organisms, stemming from a common problem faced by geneticists, physicists, and chemists alike. It combines experiential aspects of genetics, physics, and chemistry to answer questions and solve problems that scientists could not figure out before. 

Without molecular biology, the mechanisms of genes—what exactly they are and how they behave—would have remained largely unknown. The molecular biologists who discovered the DNA double helix were the ones who  answered the question of how exactly sequences of DNA turned into proteins.  Without using methods established through the advancement of molecular biology, this discovery would not have been possible.

Molecular biology originated in the 1930s and 40s, making it a relatively new scientific field. Warren Weaver, director of the Division of Natural Sciences at the Rockefeller Foundation, coined the term “molecular biology” in 1938 in a report for the Foundation.

The field came to prominence in the 50s and 60s following the discovery of the DNA double helix structure by James Watson and Francis Crick (using the data found by Rosalind Franklin). The structure of biological macromolecules can be determined using techniques such as X-ray crystallography, as used in this case. Phoebus Levene was another important contributor to the modeling of DNA, who put forward the idea of the “polynucleotide model” of DNA in 1919 as a result of his biochemical yeast experiments.

The discovery of DNA’s structure, comprising four types of nucleotides allowed scientists to focus on researching how the information contained in the structure is involved in classical and molecular genetics and protein synthesis. This research eventually led to our modern understanding of the chemical processes happening inside of cells.

Core Concepts of Molecular Biology, Simplified

Genes are the basis of inheritance, as they contain the “information” needed for the production of proteins. This gene information is copied during DNA replication, the process of unwinding and unzipping the double helix of DNA, then matching complementary base pairs to form two identical copies of the original DNA. 

This DNA is then transcribed into messenger RNA (mRNA) from the DNA template, using RNA polymerase. The mRNA is then translated into proteins by ribosomes. All of these mechanisms are central to the study of molecular biology as they give scientists a closer look at the “information” that is encoded in genes and how it is used.

In order to understand these mechanisms, the 3D shape of biological macromolecules needs to be understood first. This can be done using many different molecular biology techniques, including X-ray diffraction analysis, gel electrophoresis, electron microscopy, and western blots, in addition to molecular cloning and transcription techniques like polymerase chain reaction (PCR) and reverse-transcription PCR (RT-PCR). Scientists can better understand the molecular basis of genetic processes using any number of these molecular techniques, depending on their goal.

The use of such methods later led to genetic engineering, an important and up-and-coming method of treating disease. Genetic engineering involves utilizing the tools provided by molecular biology to specifically alter an organism’s genetic makeup.

Techniques Developed Out of Molecular Biology

Sometimes, biological processes do not function as they are supposed to, leading to health problems and disease. Molecular biology created a solid foundation for the understanding of how biological processes happen inside of cells, and had a major impact on biotechnology.

Since we now understand what these molecular processes are and how they work, scientists have figured out ways to positively alter or introduce new pathways and processes into cells in order to treat individuals affected by these conditions. In fact, molecular biology has both complimented and improved older applications like biochemistry and genetics that have been around before its development.

Genetic engineering

Molecular biologists and biochemists, in seeking to understand genetic processes and gene expression, eventually led to the development of genetic engineering, which involves the isolation, sequencing, replication, and modification/expression of specific genes and nucleic acids in organisms. 

The gene that is to be modified/expressed is identified in the organism’s DNA using restriction enzymes, a class of enzymes that were discovered in the 60’s that cut DNA at specific sequences, allowing scientists to pinpoint and isolate the exact gene they’re looking for. 

There are about 3,000 different kinds of restriction enzymes that cut at different DNA sequences. Once isolated, PCR is used to amplify the gene, and these amplified sequences can then be inserted into plasmids, forming recombinant DNA. This plasmid can be transformed into bacteria cells which make clones as they divide and multiply. 

Usually, an antibiotic-resistant gene is added to the plasmid to identify bacteria colonies containing the gene of interest after multiplication. It is then possible to induce the bacteria cells to express the inserted gene, producing the protein of interest. 

Gene Therapy

Gene therapy is another discipline in molecular biology that has been developed to modify, enhance, or suppress certain genes in an organism in order to treat or prevent disease, rather than relying on drugs to support immune responses and the nervous system.

It is a relatively new discipline, and most gene therapies are not even available for use yet. Nonetheless, it does show promise in successfully targeting and treating a lot of debilitating diseases. 

Despite its potential, some see editing genes as controversial due to the unknown short- and long-term effects, as well as the ethics of manipulating a person’s genetic makeup. Despite this, it could potentially help develop life-saving treatments for otherwise untreatable or incurable diseases that current therapies are powerless against.

Currently, the primary way to receive gene therapy treatment is through clinical trials. New genetic material made of the correct gene being targeted is introduced into a person’s cells in order to help the cell function properly despite the defective gene. 

It’s possible to use an entirely different gene as well, one that produces proteins that facilitate the same cell function. In order to insert the material into the cell, a vector is used to carry and deliver it—directly injecting rarely works. Viruses are commonly used as vectors, as they can infect cells, delivering the genetic information either directly into the chromosome or into the cell’s nucleus. 

When they are used in this way as vectors, they are modified to remove their original gene structure, preventing them from causing disease. However, there are risks involved with this method. 

The virus could possibly regain the ability to cause an infection or the body could recognize these vectors as foreign, eliciting an unwanted immune response. It is also possible for the virus to infect the wrong cell type or insert the gene in the wrong place, which could lead to healthy cells being damaged and even the formation of cancer. 

Newer techniques are being thought of every day in order to minimize these potential risks and safely deliver life-saving gene-editing tools to affected cells.

How Will Molecular Biology Continue to Develop? 

Molecular biology is a relatively recent field in science that came to prominence in the mid-1900’s due to important scientific discoveries that allowed scientists to visualize the structures of biological macromolecules and better understand molecular mechanisms and processes. It has had a major impact on other fields as well, including developmental biology, immunology, evolutionary biology, ecology, and molecular neuroscience.

Since its initial introduction and development, many different techniques have been created to further understand the processes of how DNA and proteins interact and function in cells, and studies including biochemistry and cell biology continue to increase our understanding of cell function on a microscopic and molecular level. 

This has led to the creation of cutting-edge genome editing techniques such as genetic engineering and gene therapy, which could possibly be the answer to treatment for some debilitating diseases. 

Molecular biology is also ever-evolving, with new and exciting things happening every day that progress our knowledge of how cells function. Whether it is a connection in the way cancer cells and immune cells function or a computer modeling exactly what is happening in cells, the boundaries of this research are constantly expanding and new possibilities are being explored every day in the biological sciences.