Reflection on Mendel after decades
Fun Fact: People had been selectively breeding plants long before we ever conceived the notion of genes and genetics.
By the April of 2003, after 13 years of painstaking work by 20 research institutions, we finally had, for the very first time, a complete map of the human genome consisting of ~ 3.4 billion base pairs. This was a huge accomplishment as it brought us closer to understanding the genetic makeup of us humans. But the interest in genetics had started a long time before that, and humans had been relying on genetics even longer than that — through selective breeding. Today, genetics is a huge area in all life sciences. For example, we relied on genetics for the discovery of SARS-CoV-2, and its vaccine.
Selective breeding in plants led to their domestication by selecting for desirable traits such as fruit taste, plant height, seed colour, etc. Almost all plants used today had been domesticated at some point in history. The practice of selective breeding dates back 9,000–11,000 years when farmers used to breed plants with desirable qualities with each other. While breeding was very common practice by the 1900s, their biological understanding was unknown for quite some time. This lack of knowledge of breeding bothered Gregor Mendel, an Australian monk who was posthumously known as the Father of Genetics.
Mendel was interested to find out how traits transferred from one generation to the next; and for his studies, he used pea plants (Pisum sativum). The common theory to explain inheritance until the end of the 19th century was the Blending Theory of Inheritance — which claimed that traits of the parents were blended in the progeny. Of course, we now know today that this theory is false.
For his study, Mendel chose different observable traits of pea plants such as plant height, pod colour, seed shape, etc and he obtained similar observations with each of these traits. He observed that when true-breeding yellow pea and true-breeding green pea and were crossed together, their offspring only produced yellow pea. However, the green pea trait was not lost, it reappeared in the next generation with the ratio of 1 green pea : 3 yellow pea. He concluded from these observations that there are certain invisible “factors” that determine whether a certain trait is going to be dominant over the other, in this case, the trait for yellow peas seems to be dominant over the trait for green peas. These factors are now known as genes.
Mendel shared his results to then-well-known scientists who were studying heredity at the time such as Hugo de Vries and Carl Nägeli; his results were later published in The Proceedings of the Brünn Natural Science Society in 1865. Carl Nägeli was interested in Mendel’s work but was working with hawkweed at the time. He asked Mendel to replicate his results in hawkweed but Mendel was unable to do so. We now know that this was because hawkweed can replicate asexually whereby the offspring is the clone of its parent. This failure to replicate his results made him doubt the significance of his findings, which caused Mendel’s work to soon be forgotten until later revived by William Bateson.
William Bateson was the first person to name the “factor” of inheritance, as described by Mendel — a gene. He fully recognized the importance of Gregor Mendel’s scientific work, and further discovered epistasis, homeotic mutations and genetic linkage.
The “factors” that Mendel once thought were invisible are now crystal clear. Genes are the building blocks of proteins that regulate all of life (as we know it). Today, the study of genes play a vital role in life sciences. For example, the main push after the initial discovery of the SARS-CoV-2 was for scientists to sequence its genome. The sequence provided a greater insight into the virus including the fact the SARS-CoV-2 is 79.5% similar to the SARS-CoV-1 virus — which caused an epidemic in 2003 (Peng et al., 2020).
USEFUL RESOURCES
- Timeline: History of genomics (https://www.yourgenome.org/facts/timeline-history-of-genomics)
WORKS CITED
Leathers, G. (2017). Genetics, and the precise, past-paced world of plant breeding. CountryGuide. Crops. Retrieved from https://www.country-guide.ca/crops/genetics-and-the-precise-past-paced-world-of-plant-breeding/
Peng, Z., Xing-Lou, Y., Xian-Guang, W., Ben, H., …, Yan-Yi, W., Geng-Fu, X, Zheng-Li, S. (2020). Discovery of a novel coronavirus associated with the recent pneumonia outbreak in 3 humans and its potential bat origin. bioRxiv. doi: http://dx.doi.org/10.1101/2020.01.22.914952
