Telogen
Definition
The resting phase of the hair cycle, lasting two to four months in scalp hair. The root forms a club-shaped, non-pigmented bulb. Telogen hairs shed passively and carry no viable nucleated root cells; only mitochondrial DNA can be recovered from the shaft.
- Phase
- Resting phase of the hair growth cycle
- Duration (scalp)
- Two to four months
- Root appearance
- Club-shaped, non-pigmented bulb
- DNA recoverable
- Mitochondrial DNA only from the shaft
Common questions
Why can't nuclear DNA typically be obtained from a shed telogen hair?+
A telogen hair has already detached from the follicle's blood and nutrient supply and lacks the nucleated root sheath cells present in an actively growing anagen hair, so there is generally no viable source of nuclear DNA left, leaving only the mitochondrial DNA present along the shaft.
How does finding a telogen hair at a scene affect the investigative value of the evidence?+
Because only mitochondrial DNA is typically recoverable, a telogen hair can support inclusion or exclusion within a maternal lineage but cannot individualize a source the way a full nuclear STR profile can, so it is treated as more limited, corroborative evidence rather than a standalone identification.
Related terms
- Anagen
- The active growth phase of the hair cycle, lasting two to six years in scalp hair. During anagen the root matrix is...
- Cortex
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- Cuticle
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- Follicular Tag
- Translucent sheath tissue adhering to the root of a forcibly pulled hair. Contains nucleated epithelial cells from the inner root sheath and...
- Medulla
- The central canal of the hair shaft, which may be continuous, interrupted, fragmented, or absent. Medullary pattern and the medullary index (medulla...