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Related Concept Videos

Overview of Transposition and Recombination02:13

Overview of Transposition and Recombination

Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in speciation by changing genome sizes and modifying gene expression patterns. For example, in bacteria, transposition can lead to conferring antibiotic resistance. Movement of transposable elements within the genetic pool of pathogenic bacteria can aid in transfer of antibiotic-resistant genetic elements. In eukaryotes, transposons can carry out...
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Gene Conversion

Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
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Other than maintaining genome stability via DNA repair, homologous recombination plays an important role in diversifying the genome. In fact, the recombination of sequences forms the molecular basis of genomic evolution. Random and non-random permutations of genomic sequences create a library of new amalgamated sequences. These newly formed genomes can determine the fitness and survival of cells. In bacteria, homologous and non-homologous types of recombination lead to the evolution of new...
Point and Frameshift Mutations01:30

Point and Frameshift Mutations

Point mutations are genetic alterations involving the change of a single nucleotide base pair in DNA. Depending on how the alteration affects protein synthesis, they can lead to various consequences.Point mutations fall into the following types:Silent mutations occur when a nucleotide change does not alter the amino acid sequence due to the redundancy of the genetic code. For instance, changing ACC to ACA still encodes threonine, leaving the protein function unaffected. This occurs because...
Transposons01:24

Transposons

Transposons, or "jumping genes," are small mobile genetic elements (MGEs) that range from 700 to 40,000 base pairs in length. They are found in all organisms and can move within the same chromosome or transfer to different chromosomes. In some cases, transposons can also jump between different host DNA molecules, such as plasmids or viruses, contributing to genetic variability.Barbara McClintock first discovered these mobile genetic elements in the 1940s while studying maize genetics, and she...
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DNA-only Transposons

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Genetic Mapping of Thermotolerance Differences Between Species of Saccharomyces Yeast via Genome-Wide Reciprocal Hemizygosity Analysis
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Transition-transversion bias is not universal: a counter example from grasshopper pseudogenes.

Irene Keller1, Douda Bensasson, Richard A Nichols

  • 1School of Biological and Chemical Sciences, Queen Mary, University of London, London, United Kingdom. irene.keller@vogelwarte.ch

Plos Genetics
|February 6, 2007
PubMed
Summary

This study challenges the universal assumption of a transition bias in DNA mutations. Researchers found no significant transition bias in grasshoppers, suggesting species-specific differences in mutation processes.

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Area of Science:

  • Genomics
  • Evolutionary Biology
  • Molecular Evolution

Background:

  • Metazoan DNA sequence comparisons reveal a bias towards transitional over transversional substitutions.
  • This bias is partly attributed to methylated cytosine mutations and postmutation selection processes like codon usage.
  • A universal transition bias is generally assumed, but empirical evidence is limited to Drosophila and Mammalia.

Purpose of the Study:

  • To investigate the point substitution spectrum in a third metazoan group, Podisma pedestris (grasshopper).
  • To determine if a universal transition/transversion bias exists across different taxa.
  • To explore interspecific variations in DNA point substitution processes.

Main Methods:

  • Analysis of DNA sequences from two pseudogene families in Podisma pedestris.
  • Surveying mutation accumulation in nuclear mitochondrial and ribosomal DNA sequences.
  • Characterizing the point substitution spectrum, accounting for methylation effects.

Main Results:

  • Cytosine-guanine (CpG) dinucleotides showed high transition frequencies, as expected from methylated sites.
  • Transition rates at other cytosine residues were significantly lower.
  • After correcting for methylation, no significant difference was found between transition and transversion rates.

Conclusions:

  • The hypothesis of a universal transition/transversion bias is rejected based on these findings.
  • Fundamental interspecific differences in point substitution processes are suggested.
  • The study highlights the need for broader taxon sampling to understand mutation patterns.