Answer:
Medulla.
By analyzing the DNA extracted from the hair follicle, the medullary index and the pattern of medulla in the hair samples obtained from a crime scene, an investigator can identify the owner.
Step-by-step explanation:
The hair consists of follicle and shaft. The follicle is the part of the skin, where the hair grows and the hair shaft has three layers: an inner medulla, a cortex, and an outer cuticle.
The morphology (physical characteristics) of hair provides a broad detail on the racial background of an individual and an investigator can identify a group of people who share similar traits. But the hair without follicle cells attached to it, cannot be used to identify a specific individual. If the follicle of a hair is present, then it can lead to individual identification by DNA analysis. Also the medulla of animals is larger than that in the humans. By comparing the medullary index (the ratio of the diameter of the medulla to the diameter of the entire hair), it can be determined if the hair obtained from crime scene belongs to animals or humans. The macroscopic (length, color, and curliness) and microscopic characteristics ( pattern of the medulla, pigmentation of the cortex, and types of scales on the cuticle) of the hair samples are studied during a crime investigation. If the entire hair follicle (follicular tag) is present in the hair samples found at the crime scene, the blood and tissue attached to the follicle is extracted and analyzed using DNA profiling. DNA analysis of the hair follicle provides an identification with greater accuracy than the hair shaft.