Geneticist Susumu Ono proposed in 1972 that just as the Earth has fossil remains of extinct species, our genome is filled with molecular fossils, or remnants of extinct genes. One such example is the gulop gene, which allowed our early primate ancestors to produce vitamin C. However, around 61 million years ago, the gulop gene became a pseudogene, a non-functional molecular fossil, after a mutation inactivated it. This meant that our ancestors had to obtain vitamin C from their diet instead of producing it themselves.
Similarly, around 17 million years ago, the uox gene, which coded for the uricase enzyme that breaks down uric acid, became a pseudogene. This has led to high uric acid levels in humans and other apes, making us more prone to diseases like gout.
Research has shown that the loss of these genes may have given our ancestors an evolutionary advantage. For example, the loss of the uox gene allowed our ancestors to store fat more efficiently, which was beneficial during times of food scarcity.
Our genomes also contain many pseudogenes related to taste receptors, including bitter taste receptors. The loss of these genes may have been due to changes in our diet and eating habits, such as the increased consumption of meat and the use of fire for cooking.
Overall, the study of molecular fossils and pseudogenes provides insights into our evolutionary history and how our genomes have changed over time in response to environmental pressures.
Here are the key facts from the text:
1. In 1972, geneticist Susumu Ono wrote that the human genome is filled with the remains of extinct genes.
2. The human genome contains molecular fossils, which are bits of DNA that are broken and no longer work.
3. One of these molecular fossils is a gene called GULOP, which is located on the eighth chromosome.
4. GULOP used to code for an enzyme that helped early primate ancestors make their own vitamin C.
5. The GULOP gene became a pseudogene around 61 million years ago, during the Paleocene epoch.
6. The death of the GULOP gene meant that early primates had to get vitamin C from their diet instead of making it themselves.
7. Lemurs, which are more distant primate cousins, can still make their own vitamin C because the GULOP gene did not become a pseudogene in their lineage.
8. The human genome contains thousands of pseudogenes, which are genes that have become non-functional over time.
9. Pseudogenes can result from gene duplication events or from mutations that inactivate a gene.
10. The GULOP gene is a unitary pseudogene, meaning that there was only one copy of the gene in the genome and it became non-functional over time.
11. The loss of the GULOP gene was likely not a significant disadvantage for early primates because they were able to get vitamin C from their diet.
12. The human genome contains over 20,000 pseudogenes, which is a number that rivals the number of active genes.
13. Many pseudogenes are the result of ancient gene duplication events.
14. The process of gene death can occur through mutations that inactivate a gene, and this process is a natural part of evolution.
15. The loss of a gene can be beneficial or neutral, depending on the environment and ecological context.
16. The UOX gene, which coded for the uricase enzyme, became a pseudogene around 17 million years ago.
17. The uricase enzyme helps to break down uric acid, a waste product of metabolism.
18. The loss of the UOX gene may have given early primates an evolutionary advantage by allowing them to store fat more efficiently.
19. The human genome contains 25 working bitter taste receptor genes, each of which is thought to be associated with tasting specific families of compounds.
20. We have also lost 11 bitter taste receptor genes, two of which died relatively recently, sometime after our last common ancestors with chimpanzees and bonobos.
21. The death of these two bitter taste receptor genes may have occurred because they were no longer necessary for our survival, given the changes in our diet and environment.
22. The human genome contains molecular fossils that preserve our evolutionary legacy in the form of extinct genes.
23. The study of pseudogenes can provide insights into the evolutionary history of a species.
24. The human genome is a historical record of our evolutionary past, containing both functional and non-functional genes.
25. The genome is not just a recipe book for building an organism, but also a molecular fossil bed that preserves our evolutionary legacy.