T.15 Origen y evolución de los intrones

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Questions and Answers

What is the primary function of spliceosomes in splicing mechanisms?

  • To increase genetic diversity through exon shuffling
  • To regulate gene expression through alternative splicing
  • To remove introns and join exons (correct)
  • To remove exons and join introns

According to the Intron-late Theory, how did introns originate in eukaryotes?

  • Through the action of self-splicing introns
  • Through a process of gene duplication and exon shuffling (correct)
  • Through the action of spliceosomes
  • Through horizontal gene transfer from prokaryotes

What is one way that introns can regulate gene expression in eukaryotes?

  • By increasing genetic diversity through exon shuffling
  • By playing a role in the evolution of new gene functions
  • By influencing genome size
  • By regulating transcription through alternative splicing (correct)

What influences intron evolution rates across different eukaryotic lineages?

<p>Gene expression level, gene function, and genome size (C)</p> Signup and view all the answers

What is one observation that supports the Intron-early Theory?

<p>Some ancient eukaryotic genes still retain introns (B)</p> Signup and view all the answers

What is the main difference between spliceosomal introns and self-splicing introns?

<p>Spliceosomal introns require spliceosomes, while self-splicing introns do not (C)</p> Signup and view all the answers

What is the primary function of the genes that were present in the early stages of evolution?

<p>To code for proteins with basic functions such as kinases and calcium binding (C)</p> Signup and view all the answers

What happens to the exons when an intron moves?

<p>The exons are carried along with the intron (D)</p> Signup and view all the answers

What is the proposed mechanism by which proteins evolved in eukaryotes?

<p>By shuffling existing protein domains (D)</p> Signup and view all the answers

What is the result of the shuffling of exons?

<p>A gain of protein function (B)</p> Signup and view all the answers

What is the challenge in studying the evolution of eukaryotic genes?

<p>The passage of time, which has erased many historical signals (B)</p> Signup and view all the answers

What is the theory that suggests that eukaryotic genes evolved by shuffling exons?

<p>Exon-shuffling Theory (B)</p> Signup and view all the answers

What is the characteristic of the proteins that result from the shuffling of exons?

<p>They are composed of multiple functional domains (D)</p> Signup and view all the answers

What is the evidence that supports the idea of exon shuffling?

<p>The existence of functional domains in eukaryotic proteins (C)</p> Signup and view all the answers

What is the implication of the exon-shuffling theory for protein evolution?

<p>It is easy to evolve new protein functions (A)</p> Signup and view all the answers

What is the most likely explanation for the widespread presence of introns in eukaryotes?

<p>Introns were present in LUCA and were lost in eubacteria and archaea (C)</p> Signup and view all the answers

What is the implication of the homology between spliceosomal introns and type II introns?

<p>They share a common origin and have diversified (A)</p> Signup and view all the answers

What is a possible way that introns can move and perpetuate themselves in eukaryotic genomes?

<p>By retrotranscribing themselves into DNA (B)</p> Signup and view all the answers

What is the significance of the presence of introns in eukaryotes?

<p>It implies that eukaryotes have been able to exploit introns for their benefit (B)</p> Signup and view all the answers

What is one of the possible ways that introns can facilitate the evolution of proteins with new functions?

<p>By facilitating the shuffling of exons and protein domains (B)</p> Signup and view all the answers

What is the possible origin of introns according to the Intron-early Theory?

<p>They were present in LUCA and were lost in eubacteria and archaea (B)</p> Signup and view all the answers

What is the term for the process by which introns can move from one mitochondrial genome to another?

<p>Mitochondrial fusion (C)</p> Signup and view all the answers

What is the difference between type I and type II introns?

<p>Type I introns have a higher degree of homology with each other (D)</p> Signup and view all the answers

What is the implication of the presence of introns in eukaryotes for our understanding of the evolution of gene expression?

<p>It indicates that eukaryotes have a more flexible gene expression system (A)</p> Signup and view all the answers

What is the term for the hypothesis that introns are not ancient, but rather appeared later in eukaryotic evolution?

<p>Intron-late theory (C)</p> Signup and view all the answers

What is one of the ways that introns can be inserted into DNA?

<p>Through the action of DNases (D)</p> Signup and view all the answers

What is the relationship between the RNA world and the origin of introns?

<p>The RNA world is a prerequisite for the origin of introns (A)</p> Signup and view all the answers

What is the significance of the conservation of introns in eukaryotes?

<p>It implies that introns are involved in the regulation of gene expression (D)</p> Signup and view all the answers

What is the term for the process by which different exons can be combined to form different proteins?

<p>Alternative splicing (C)</p> Signup and view all the answers

What is one of the reasons why it is difficult to determine the origin of introns?

<p>Because there is limited evidence for the early evolution of introns (D)</p> Signup and view all the answers

What is one of the ways that introns can facilitate the evolution of eukaryotic cells?

<p>By facilitating the shuffling of exons and protein domains (A)</p> Signup and view all the answers

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Study Notes

Intron Origin and Evolution

Splicing Mechanisms

  • There are two main types of splicing mechanisms:
    • Spliceosomal introns: require spliceosomes to remove introns and join exons
    • Self-splicing introns: can remove themselves without the need for spliceosomes
  • Splicing mechanisms are crucial for intron removal and exon joining in eukaryotic gene expression

Intron-late Theory

  • Proposes that introns were acquired by eukaryotes after the divergence from prokaryotes
  • Suggests that introns were introduced into eukaryotic genomes through a process of gene duplication and exon shuffling
  • This theory is supported by the observation that intron-rich genes are more common in eukaryotes than in prokaryotes

Intron Function in Eukaryotes

  • Introns can:
    • Regulate gene expression by alternative splicing
    • Increase genetic diversity through exon shuffling
    • Play a role in the evolution of new gene functions
  • Introns can also be involved in the regulation of transcription and translation

Intron Evolution Rates

  • Intron evolution rates vary across different eukaryotic lineages
  • Intron gain and loss rates are not uniform across the tree of life
  • Intron evolution rates are influenced by factors such as gene expression level, gene function, and genome size

Intron-early Theory

  • Proposes that introns were present in the earliest eukaryotes and have been lost over time in some lineages
  • Suggests that introns played a role in the evolution of early eukaryotes and the development of complex cellular processes
  • This theory is supported by the observation that some ancient eukaryotic genes still retain introns

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