Understanding DNA Fingerprinting Samples

DNA fingerprinting is a powerful technique used to identify individuals based on unique patterns in their DNA. To perform DNA fingerprinting, we need a biological sample that contains enough intact human cells, and thus, enough human DNA. The quality and quantity of DNA in the sample are crucial for successful analysis.

Evaluating Potential DNA Fingerprinting Specimens

Let's look at each option provided and determine if it can be used as a specimen for DNA fingerprinting.

• (a) Hair follicle: A hair strand itself is mostly made of a protein called keratin and does not contain nuclear DNA. However, the hair follicle (the root part of the hair) contains cells that are actively growing and have a nucleus with DNA. Therefore, hair follicles are an excellent source of DNA for fingerprinting.
• (b) Saliva: Saliva contains buccal cells, which are shed from the lining of the mouth. These cells have a nucleus and contain human DNA. Although the amount of DNA can vary depending on the sample collection, saliva is commonly used as a specimen for DNA fingerprinting, especially in non-invasive collections.
• (c) Skin tissue: Skin tissue is made up of various cells, including epithelial cells and fibroblasts, all of which contain nuclei and thus human DNA. A small piece of skin tissue is a very good source of DNA for fingerprinting and is often used in forensic investigations.
• (d) Food from stomach: Food found in the stomach is primarily the ingested meal in various stages of digestion. While this food might contain some cells from the person who ate it (like shed epithelial cells), these would be mixed with the food particles themselves, digestive enzymes, stomach acid, and potentially other organisms (bacteria, etc.). The amount of human DNA present would be very low and likely degraded due to the harsh environment of the stomach and the presence of digestive enzymes. Moreover, extracting sufficient, pure human DNA from this complex mixture is very difficult and often not feasible for reliable DNA fingerprinting compared to dedicated cellular samples.

Conclusion on Suitable Specimens

Based on the presence of sufficient, usable human DNA, hair follicles, saliva, and skin tissue are all suitable specimens for DNA fingerprinting. Food from the stomach, however, is generally not a reliable source due to low quantities of potentially degraded human DNA mixed with a complex matrix.

Revision Table: Suitability of Samples for DNA Fingerprinting

Additional Information on DNA Fingerprinting Samples

Many types of biological evidence can be used for DNA fingerprinting in forensic science or other applications. These include any sample that contains nucleated human cells. Common samples include:

• Blood (white blood cells)
• Semen
• Vaginal secretions
• Mucus
• Bone
• Teeth
• Urine (if cellular debris is present)
• Feces (can contain shed cells, but like stomach contents, can be challenging)
• Tissue from internal organs
• Buccal swabs (swabs from inside the cheek, similar to saliva)

The success of DNA fingerprinting from a sample depends not only on the type of sample but also on how it was collected, stored, and handled, as these factors can affect DNA preservation and integrity.