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Related Concept Videos

Evolutionary Relationships through Genome Comparisons02:54

Evolutionary Relationships through Genome Comparisons

Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is that if two species share a common feature, it is likely encoded by the DNA sequence conserved between both species. The advent of genome sequencing technologies in the late 20th century enabled scientists to understand the concept of conservation of domains between species and helped them to deduce evolutionary relationships across diverse...
Modern Molecular Taxonomy01:29

Modern Molecular Taxonomy

Advancements in molecular biology have revolutionized the identification and characterization of bacteria, with multiple methods leveraging DNA sequencing for enhanced precision. As sequencing technologies improve and costs decline, these approaches are increasingly used in clinical, environmental, and evolutionary studies.Multilocus Sequence Typing (MLST) examines several housekeeping genes, essential chromosomal genes encoding cellular functions, to distinguish strains. Approximately...
Sign Test for Matched Pairs01:17

Sign Test for Matched Pairs

The sign test for matched pairs offers a robust method for comparing two paired samples, often for the effects of an intervention in one of them. This method is very useful in situations where the underlying distribution of the data is unknown. The test compares two related samples—often pre- and post-treatment measurements on the same subjects—to determine if there are significant differences in their median values.
To conduct the sign test, we first calculate the differences in value between...
Maxam-Gilbert Sequencing01:05

Maxam-Gilbert Sequencing

In the same year as the discovery of the Sanger sequencing method, another group of scientists, Allan Maxam and Walter Gilbert, demonstrated their chemical-cleavage method for DNA sequencing. The Maxam-Gilbert method relies on using different chemicals that can cleave the DNA sequence at specific sites, the separation of resulting DNA fragments of variable size using electrophoresis, and deciphering the DNA sequence from the resulting gel bands.
Challenges of the Maxam-Gilbert Method
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Per-Unit Sequence Models01:26

Per-Unit Sequence Models

An ideal Y-Y transformer, grounded through neutral impedances, displays per-unit sequence networks akin to those of a single-phase ideal transformer when subjected to balanced positive- or negative-sequence currents. These currents do not produce neutral currents, and their associated voltage drops.
Zero-sequence currents, which are identical in magnitude and phase, generate a neutral current, resulting in voltage drops across the neutral impedance and the low-voltage winding. If the...
Multiple Comparison Tests01:13

Multiple Comparison Tests

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Related Experiment Video

Updated: May 18, 2026

RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level
11:04

RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level

Published on: May 19, 2019

Sequence comparison alignment-free approach based on suffix tree and L-words frequency.

Inês Soares1, Ana Goios, António Amorim

  • 1Faculdade de Ciências da Universidade do Porto, 4169 Porto, Portugal. isoares@ipatimup.pt

Thescientificworldjournal
|September 22, 2012
PubMed
Summary

This study introduces an alignment-free sequence comparison method using generalized suffix trees and L-word frequency analysis. It offers a fast, efficient alternative for analyzing genetic data, particularly mitochondrial genomes.

Related Experiment Videos

Last Updated: May 18, 2026

RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level
11:04

RNA Next-Generation Sequencing and a Bioinformatics Pipeline to Identify Expressed LINE-1s at the Locus-Specific Level

Published on: May 19, 2019

Area of Science:

  • Bioinformatics
  • Computational Biology
  • Genomics

Background:

  • Traditional sequence comparison methods often rely on sequence alignment, which can be challenging or impossible with abundant gaps (insertions/deletions).
  • Alignment-free approaches offer a valuable alternative when alignment is difficult, addressing limitations of evolutionary assumptions.

Purpose of the Study:

  • To develop and present an improved alignment-free method for sequence comparison.
  • To enhance word counting approaches by optimizing word length and integrating suffix tree structures.

Main Methods:

  • Computation of a generalized suffix tree for all sequences in linear time.
  • Rapid calculation of L-word frequencies within each sequence using the suffix tree.
  • Generation of a genetic distance matrix via pairwise Euclidean distance based on L-word profiles.
  • Determination of an optimal word length for improved accuracy.

Main Results:

  • The developed method provides a fast and simple application for sequence comparison.
  • The approach proved efficient and powerful when applied to mitochondrial genomes.
  • The method successfully generates genetic distance matrices for phylogenetic analyses (e.g., neighbor joining dendrograms, multidimensional scaling graphs).

Conclusions:

  • The improved alignment-free method offers a robust alternative to traditional alignment-based sequence comparison.
  • The integration of suffix trees and optimized word length enhances the efficiency and power of word counting techniques.
  • The freely available Python implementation facilitates its application in genomic research, especially for mitochondrial genomes.