Related Experiment Video
Updated: Aug 14, 2026

A Practical Guide to Phylogenetics for Nonexperts
Published on: February 5, 2014
Scoring pairwise genomic sequence alignments
F Chiaromonte1, V B Yap, W Miller
1Department of Statistics, Penn State, University Park, PA 16802, USA. chiaro@stat.psu.edu
Abstract:
The parameters by which alignments are scored can strongly affect sensitivity and specificity of alignment procedures. While appropriate parameter choices are well understood for protein alignments, much less is known for genomic DNA sequences. We describe a straightforward approach to scoring nucleotide substitutions in genomic sequence alignments, especially human-mouse comparisons. Scores are obtained from relative frequencies of aligned nucleotides observed in alignments of non-coding, non-repetitive genomic regions, and can be theoretically motivated through substitution models. Additional accuracy can be attained by down-weighting alignments characterized by low compositional complexity. We also describe an evaluation protocol that is relevant when alignments are intended to identify all and only the orthologous positions. One particular scoring matrix, called HOXD70, has proven to be generally effective for human-mouse comparisons, and has been used by the PipMaker server since July, 2000. We discuss but leave open the problem of effectively scoring regions of strongly biased nucleotide composition, such as low G + C content.
Related Concept Videos
DNA Base Pairing
Evolutionary Relationships through Genome Comparisons
Multi-species Conserved Sequences
Although the genome of each species varies greatly from each other, a few sequences are highly conserved. Such conserved DNA...
Comparing Copy Number Variations and SNPs
Copy number variations or CNVs are the structural variations that cover more than 1kb of DNA sequence. The single nucleotide polymorphism (SNP), on the other hand, is a single nucleotide change or a point mutation that is found in more than 1%...
Genome Annotation and Assembly
Wilcoxon Signed-Ranks Test for Matched Pairs

