Genetic marker

File:SFP discovery principle.jpg

SFP discovery principle for gene probing

A genetic marker is a specific gene or DNA sequence with an established position on a chromosome, useful for identifying individuals or species. Originating from genomic loci variations due to mutation or alterations, these markers can range from short DNA sequences like SNPs to longer sequences such as minisatellites.

Background

Historically, gene mapping predominantly utilized traditional genetic markers. These markers represent genes encoding visible traits, like blood types or seed shapes. However, the paucity of such observable characteristics in many organisms curtailed the scope of mapping endeavors.

Types of Genetic Markers

The array of genetic markers includes:

• RFLP - Restriction fragment length polymorphism
• SSLP - Simple sequence length polymorphism
• AFLP - Amplified fragment length polymorphism
• RAPD - Random amplification of polymorphic DNA
• VNTR - Variable number tandem repeat
• SSR - Microsatellite polymorphism or Simple sequence repeat
• SNP - Single nucleotide polymorphism
• STR - Short tandem repeat
• SFP - Single feature polymorphism
• DArT - Diversity Arrays Technology
• RAD markers - Restriction site associated DNA markers

Furthermore, molecular genetic markers fall into two categories:

1. Biochemical markers – Detect variations at the gene product level, such as alterations in proteins and amino acids.
2. Molecular markers – Detect DNA level variations, encompassing nucleotide changes like deletion, duplication, inversion, and insertion.

The inheritance of markers can be dominant/recessive or co-dominant. Co-dominant markers, distinguishable between homozygotes and heterozygotes, are generally more informative.

Applications

• Medical research: Genetic markers aid in researching the connection between hereditary diseases and their genetic origins, like a specific gene mutation causing a protein defect.
• Ancestry analysis: In genetic genealogy, genetic markers estimate genetic distances between individuals or populations. They can identify maternal or paternal lineages through uniparental markers, or trace all ancestries via autosomal markers.
• Genome study: Markers are pivotal in creating genetic maps for the studied organism. Techniques include RFLP, AFLP, RAPD, and SSR.
• Disease investigation: Genetic markers proved crucial in determining the transmissible agent of CTVT, solidifying the idea of the tumor cell evolving into a transmissible parasite.
• Livestock selection: Markers measure the genomic response to selection in livestock, signifying the genetic makeup change in cells due to natural or artificial selection.

Significance

For a genetic marker to be effective, it must be:

• Easily identifiable
• Associated with a particular locus
• Highly polymorphic (as homozygotes offer no information)

Markers can be detected directly, through RNA sequencing, or indirectly, using allozymes.

See Also

• Gene Mapping
• Chromosome
• DNA Sequencing
• Genomic loci

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