2.3 Genetics and Cell Biology
KEY CONCEPTS
By the end of this section, you will be able to do the following:
- Explain the role of genetics in helping us understand how information is transmitted within a cell and between cells
- Describe what scientific discoveries were critical to the development and support of the Central Dogma of Molecular Biology
- Evaluate how genetic techniques such as CRISPR and bioinformatics can be used to answer questions about how cells function
At some point in your biological career, you’ve probably heard DNA referred to as the “blueprint of the cell” – a set of instructions to build the cell, all of its components, and all of the functions of those components. It took many years of experiments to understand this relationship between DNA and cell structure and function. In this chapter section, we’ll summarize some of the research discoveries that led to our current understanding of how information (DNA) is transmitted between and within cells, as well as a few modern genetic techniques that continue to improve our understanding of cell biology.
Transmission of Information between Cells
Weirdly enough, the field of genetics began before we even knew what genes were! One of the earliest things genetics students learn about is Gregor Mendel and his studies with pea plants, which were important for establishing that traits (characteristics) could be inherited (passed down) from parents to offspring. However, Mendel did not know what sort of substance was responsible for this inheritance because it was the 1860s, and science had not progressed to that point yet. We now know that genetic (hereditary) information is transmitted from parent to offspring via chromosomes – long strands of DNA wrapped around proteins and found in the nucleus (Figure 2.14). There are usually multiple chromosomes within each eukaryotic cell (the number varies among species) and these chromosomes contain the information needed to build and operate a cell.
This idea that chromosomes carry hereditary information was first articulated in the 1880s by at least two scientists (Wilhelm Roux, August Weissman). This idea was formalized into the chromosomal theory of inheritance in the early 1900s when several scientists started making the connection between Mendel’s work and the growing information about chromosomes. Many threads of evidence were required to support the chromosomal theory of inheritance, including those that used microscopy and biochemistry. Chromosomes were first discovered in the 1880s by Walther Flemming, who used microscopy to make careful observations of mitosis – the process by which one cell divides its genetic material into two daughter cells. In the early 1900s, work by Thomas Hunt Morgan and his students showed that specific traits in Drosophila fruit flies were associated with specific chromosomes. These latter experiments made a very clear connection between genetic information and its physical location (chromosomes) within