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Rodent Genotyping

Illustration of 5.0 mm length

Rodent Genotyping

Genetic identification of research rodents is often accomplished through the use of PCR analysis of DNA extracted from tail or ear punch tissue. DNA may also be obtained from other samples, such as hair, blood and oral swabs.

Guidelines for tail tissue collection:


  1. Deviations from PSU IACUC genotyping guidelines must be described in the PI's IACUC protocol. Personnel must receive sufficient training to perform the procedures in a safe and humane manner.
  2. DNA yield from tail tissue has been shown to be highest in 10-21 day old rodents. Tail tissue analysis and identification of desired mice prior to weaning may allow more efficient use of resources. In addition, cutting through the soft tissue in the tail of a young mouse is likely to be less painful than cutting through more extensively mineralized bone and mature tissue in older animals. Tail tip collection should be performed at as young an age as feasible.
    • Animals less than 3.5 weeks of age: Collection of tail tissue may be performed without general anesthesia. Local anesthetic methods are available. Please contact an ARP veterinarian for more information.
    • Animals greater than 3.5 weeks of age: General anesthesia (e.g., isoflurane) is required when collecting tail tissue. Bleeding must be controlled and the mouse observed until it recovers from anesthesia.
  3. No more than 5 mm of tail tissue should be removed at one time from an animal. If small amounts of DNA are required, less tail tissue is needed (e.g., 2 mm). The yield of DNA does not proportionally increase as larger amounts of tail tissue are collected. Tail amputation should be done using a sharp scalpel or scissors that is disinfected between animals.
  4. Blood loss should be minimal from animals less than 3.5 weeks of age when proper procedures are used. If needed, bleeding may be controlled by applying direct pressure to the tip of the tail. Styptic powder/pencils and silver nitrate are chemical cauterizing agents that may be used if necessary. Use of heat to cauterize the tail end is not recommended.
  5. If additional tail tissue is needed from an animal, consideration should be given to using one of the alternative procedures listed below. General anesthesia is required for tail tissue collection in animals older than 3.5 weeks.

Alternatives to tail tip tissue collection:

Ear punch: The small amount of tissue collected from an ear punch is often adequate for genotyping and may be performed on any age mouse without anesthesia.

More information on collecting tissue for genotyping may be found at