The Genes We Lost Along the Way

Summary

This video explores the fascinating world of pseudogenes in the human genome, illustrating how our evolutionary history is written in our DNA. Geneticist Susumu Ohno's insights reveal that genes like GULOP and UoX, once essential for producing vitamin C and breaking down uric acid, became non-functional due to mutations. These changes reflect dietary adaptations and environmental pressures, suggesting that gene loss can sometimes enhance survival. The transcript also highlights how our taste receptors evolved alongside our changing diets, emphasizing the genomic record of our ancestral legacy. Overall, the video underscores the dynamic relationship between genetics, evolution, and food.

Takeaways

• 😀 Geneticist Susumu Ohno suggested that our genome contains fossilized remnants of extinct genes, much like fossil remains of extinct species.
• 😀 The GULOP gene, found on chromosome 8, once enabled early primates to produce their own vitamin C but became a non-functional pseudogene around 61 million years ago.
• 😀 Loss of the GULOP gene forced our primate ancestors, including tarsiers, monkeys, and apes, to obtain vitamin C from their diets, making them susceptible to diseases like scurvy.
• 😀 Our genome contains approximately 20,000 pseudogenes, rivaling the number of active genes, showing that gene loss is a significant aspect of our evolution.
• 😀 Mutations randomly occur in DNA, leading to gene inactivation, which can spread through populations if it doesn't negatively impact fitness.
• 😀 The UoX gene, which produced the uricase enzyme, became a pseudogene around 17 million years ago, resulting in higher uric acid levels in humans and other apes.
• 😀 The inactivation of UoX may have provided our ancestors with an evolutionary advantage during periods of food scarcity by promoting fat storage.
• 😀 Our taste receptors reflect dietary changes, with the death of certain bitter taste receptor genes linked to shifts in human eating habits.
• 😀 The evolution of taste receptors demonstrates how our genomes are shaped by dietary pressures, influencing which genes remain functional.
• 😀 The study of pseudogenes provides insights into our evolutionary history, showing that our genomes serve as records of both functional and non-functional genes.

Q & A

What is a pseudogene?

A pseudogene is a segment of DNA that resembles a functional gene but has lost its ability to code for a protein due to mutations.

What was the significance of the GULOP gene in early primates?

The GULOP gene allowed early primates to synthesize their own vitamin C, which was vital for their survival before it became a pseudogene around 61 million years ago.

How did the loss of the GULOP gene affect modern humans?

Since the GULOP gene became inactive, modern humans must obtain vitamin C from their diet, making them vulnerable to deficiencies such as scurvy.

What event led to the GULOP gene becoming a pseudogene?

A mutation occurred in the GULOP gene that inactivated it, preventing it from producing an enzyme necessary for vitamin C synthesis.

What role did climate changes play in the loss of the UoX gene?

As the Earth’s climate cooled, fruit became less available year-round, leading to a potential evolutionary advantage for primates with higher levels of uric acid, as it helped in fat storage during scarce food periods.

What is the function of uricase, and why is its loss significant?

Uricase is an enzyme that breaks down uric acid. Its loss in primates, including humans, leads to elevated uric acid levels, which can cause conditions like gout.

How many pseudogenes have been identified in the human genome?

Approximately 20,000 pseudogenes have been identified in the human genome, rivaling the number of active genes.

What evolutionary process allows for the spread of mutations that inactivate genes?

Mutations that do not reduce an organism's fitness can spread through genetic drift or natural selection, leading to the fixation of these mutated genes in a population.

How do changes in diet influence the evolution of taste receptor genes?

Dietary changes lead to the birth and death of taste receptor genes; for instance, carnivores often lose sweet taste receptors, while omnivores like humans retain a diverse set of taste receptors.

What was the outcome of the study on ancient uricase proteins conducted by researchers?

The study found that the ancient uricase proteins were highly efficient at processing uric acid, but mutations over time made newer versions less effective, culminating in the eventual inactivation of the UoX gene.