Introduction to HomoloGene

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Introduction to HomoloGene

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Before introduction to Homologene
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Lets tell the differences between Similarity
and Homology

• Similarity
• The extent to which nucleotide or protein
  sequences are related. The extent of similarity
  between two sequences can be based on percent
  sequence identity and/or conservation. In BLAST
  similarity refers to a positive matrix score
• Homology
• Similarity attributed to descent from a common
  ancestor

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Homology

• Orthologs and Paralogs are two types of
  homologous sequences.
• Orthology describes genes in different species
  that derive from a common ancestor. Orthologous
  genes may or may not have the same function.
• Paralogy describes homologous genes within a
  single species that diverged by gene duplication.

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Why we need the Homology database

• Identification and study of such a gene (within a
  model organism) enables properties/function of
  its analog gene in the more-complex organism to
  be inferred.

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What is the base of Homologene ?

• HomoloGene is a database of both curated and
  calculated gene orthologs and homologs for 14
  organisms including H. sapiens, M. musculus, D.
  rerio, D. melanogaster, C. elegans, A. thaliana,
  Hordeum vulgare, Oryza sativa, Z. mays.
• HomoloGene entries now include paralogs in
  addition to orthologs

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the base of Homologene

• HomoloGene entries have been augumented with
  homology and phenotype information drawn from the
  following sources
• Online Mendelian Inheritance in Man (OMIM)
  Mouse Genome Informatics (MGI)Zebrafish
  information Network (ZFIN) Saccharomyces Genome
  Database (SGD)Clusters of Orthologous Groups
  (COG)FlyBase

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If you want to search a Homologene database
UniGene ClusterIDs,LocusLink LocusIDs, gene
symbols, gene names ,nucleotide accession numbers
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Search the Homologene
Homologs
Homologene group ID
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If you dont want to query one by one
Build number
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Download the whole Homologene data
geninfo identifier
gene symbol
HomoloGene group id
Taxonomy ID
accession number
gene ID
Group5
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Lets compare Homologene with euGene

• Homologene base both on blast and experiment
• euGene base on blast
• What does that mean to biologists?

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Comparison between Homologene and euGene

• Simply base on sequence alignment does not
  provide too much information unless the sequence
  alignment results are very good
• Homologene is a larger and more reliable homologs
  database

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Thank you!