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Montezuma Quail Feathers. Credit: USFWS

Science Professionals

GENETICS UNIT

The Genetics Section of the Laboratory uses the modern techniques of molecular genetics for the identification of wildlife evidence. Plant and animal remains and products need to be identified in order to determine those conservation regulations that may apply.  Identifications include determining the taxonomic family, species, sub-species, population origin individual origin, gender origin and parentage of questioned evidence.

Nucleotide sequence analysis of mitochondrial, chloroplast and nuclear DNA identifies variants that are diagnostic markers for the taxonomic family, species, sub-species and population origin of questioned evidence. 

The nuclear DNA of animals contains short tandem repeats (STR) comprised of 2-6 base pair units that are scattered along the autosomal and sex chromosomes.  STR loci display high levels of polymorphism that is detected as length polymorphism by PCR amplification with locus-specific primers.  The amplified DNA is analyzed by direct sizing with capillary electrophoresis.  If two evidence samples exhibit the same alleles at a suite of different loci, the probability of the samples originating from the same individual is inferred from the frequency distribution of the observed alleles in a database of the species of interest.  The Genetics Section performs STR analysis for purposes of individual identification, assignment of population of origin, parentage determination and species identification.

The Genetics Section uses PCR amplification of the sex chromosome loci ZFX, ZFY and SRY to determine the gender origin of mammalian evidence.  The amplification products are analyzed by direct sizing with poly acrylamide gel electrophoresis.  Females exhibit a single ZFX amplification product originating from the two X chromosomes.  Males exhibit two differently sized amplification products: one from the ZFX and ZFY loci on the X and Y chromosomes and a second from the SRY locus exclusive to the mammalian Y chromosome.  Alternatively, in cervid, ursid, bovid and canid identifications, the SRY locus primers are included in STR multi-plexes for the simultaneous determination of individual and gender origin.

 The Genetics Section uses PCR amplification of the sex chromosome locus CHD to determine the gender origin of bird evidence.  The amplification products are analyzed by direct sizing with poly acrylamide gel electrophoresis.  Gender determination in birds differs from mammals in that females rather than males exhibit heterogamety.  CHD, the chromo-helicase binding protein, is present as a pair of duplicated gene loci on the W and Z chromosomes.  Female birds have both W and Z chromosomes, whereas males have two Z chromosomes.  The presence of the W chromosome marker is diagnostic for the female sex in most non-ratite birds.

Identifications make extensive use of the NFWFL Genetics Standards Collection of more than 4,000 individual samples from more than 800 mammal species, more than 400 bird species, 36 fish species and 50 reptile species.

The Genetics Section scientists are experts in the phylogenetic evolution, taxonomy, and biogeography of more than 150 mammal, bird, reptile and amphibian species.  They are also expert in obtaining and analyzing DNAs from such difficult plant and animal products as kiln dried wood, tanned leathers, pasteurized sturgeon caviars, antler, bone and ivory.

For more information, please view our Genetics publications.

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