What Darwin won't tell you about evolution - with Jonathan Pettitt

The Royal Institution・2 minutes read

Life's complexity in biology arises from interactions, with genetic drift and natural selection both playing significant roles in evolution and the development of complex structures; understanding genetic drift is crucial for comprehending the complexity of genomes and genetic evolution. Introns, non-coding regions in genes, and trans-splicing are examples of evolutionary traits that enhance gene expression efficiency and have essential roles in diversity and gene control in cells, showcasing how neutral events can lead to crucial biological processes.

Insights

  • Genetic drift, not just natural selection, plays a significant role in shaping genetic diversity and the fate of genetic variants within populations, impacting the complexity of biological systems.
  • Introns, non-coding regions in genes, have essential roles in gene regulation and diversity, with their origins and functions providing insights into evolutionary processes and genetic differences influenced by selection pressures.

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Recent questions

  • What role does genetic drift play in populations?

    Genetic drift can lead to the fixation or loss of genetic variants within populations, impacting genetic diversity. It influences the fate of mutations and plays a significant role in determining the survival of genetic traits. Understanding genetic drift is crucial in comprehending genetic evolution and the complexity of genomes.

  • How do introns affect gene expression?

    Introns are non-coding regions in genes that must be removed before converting RNA into protein. They have essential roles in gene mixing, diversity, and gene control in cells. Introns interrupt coding regions and need to be spliced out to produce functional proteins.

  • What is the significance of trans-splicing in gene expression?

    Trans-splicing involves replacing the front part of mRNA with a splice leader, aiding ribosome movement and translation. It becomes crucial when mutations hinder ribosome movement, ensuring proper protein expression. Trans-splicing allows for efficient gene expression and is observed in various organisms, potentially providing evolutionary advantages.

  • How does complexity in biology evolve?

    Complexity in biology can arise from genetic drift and freewheeling, contributing to the development of complex structures that may later be subject to natural selection. Genetic drift can lead to the evolution of complex traits, which then become the basis for natural selection. Constructive neutral evolution, like in trans-splicing, involves building complexity through neutral events essential for organism survival.

  • What is the relationship between population size and genetic variants?

    Population size influences genetic drift, impacting the maintenance or loss of genetic variants within a group. Simulations show how population size affects genetic diversity and the prevalence of genetic traits. Reproductive advantages or disadvantages can shape the fate of genetic variants in populations, highlighting the importance of population size in genetic evolution.

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Summary

00:00

Genetic drift shapes genetic diversity and evolution.

  • Life is complex, especially in biology, from molecules to interactions within populations.
  • Evolution is often attributed to selection, leading to more complex forms suited for survival.
  • Organisms adapt based on necessity; for example, cave fish losing eyes due to living in darkness.
  • Population size impacts genetic drift, affecting the fate of mutations within a group.
  • Genetic drift can lead to the fixation or loss of genetic variants in populations.
  • Simulations show how population size influences the maintenance or loss of genetic variants.
  • Reproductive advantages or disadvantages can shape the prevalence of genetic traits.
  • Genetic drift plays a significant role in determining the survival of genetic variants.
  • The impact of genetic drift is often underestimated, influencing genetic diversity.
  • Understanding genetic drift is crucial in comprehending the complexity of genomes and genetic evolution.

15:30

"Unraveling the Role of Introns in Genes"

  • Introns are non-coding regions in genes that must be removed before converting RNA into protein.
  • Most of the human gene consists of introns that need to be removed before being useful.
  • Eukaryotes, which are not prokaryotes, have introns interrupting their coding regions.
  • Eukaryotes are a union of alphaproteobacteria and Asgard archaea bacteria, with the former becoming mitochondria.
  • Group II introns moved around DNA after the union, interrupting genes and causing issues.
  • The last common ancestor of eukaryotes had an infestation of Group II introns.
  • Group II introns have the ability to remove themselves when converted into RNA.
  • Eukaryotes developed a complex machine to remove damaged introns that couldn't self-splice.
  • Introns have essential roles in diversity, gene mixing, and gene control in cells.
  • Population genetics can explain introns' origins and the differences in genomes due to selection pressures.

31:33

Evolutionary significance of mRNA trans-splicing

  • Messenger RNA is chemically modified with a cap that helps the ribosome recognize it and start translation at the AUG codon.
  • The stretch between the cap and AUG must be intact for efficient translation, determining the number of protein molecules produced.
  • Trans-splicing in nematodes replaces the front part of mRNA with a splice leader, aiding ribosome movement and translation.
  • Evolution of trans-splicing involves neutral events leading to the acquisition of the ability to trans-splice.
  • Trans-splicing becomes crucial when a mutation hinders ribosome movement, making it essential for proper protein expression.
  • Trans-splicing gradually becomes essential for multiple genes, leading to the majority of genes in some organisms being trans-spliced.
  • Trans-splicing is observed in various organisms, suggesting it is a recurring evolutionary trait in eukaryotic cells.
  • Trans-splicing allows for the creation of long arrays of genes, enhancing efficiency in gene expression and potentially providing evolutionary advantages.
  • Parasitic organisms like trypanosomes and schistosomes depend on trans-splicing, making them potential targets for drugs disrupting this process.
  • The concept of constructive neutral evolution, seen in trans-splicing, involves building molecular complexity through neutral events that eventually become essential for organism survival.

46:55

Genetic drift and complexity in evolution.

  • Complexity in biology cannot solely be attributed to natural selection; genetic drift can also lead to the development of complex structures that may later be subject to natural selection. Freewheeling and genetic drift can contribute to the evolution of complexity, which then becomes the basis for natural selection.
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