DNA Fingerprinting: Videos & Practice Problems

DNA fingerprinting is a powerful technique that utilizes genetic markers within a genome to identify individuals, similar to how traditional fingerprints are used. These genetic markers are specific sequences of DNA that have known locations and can be easily identified within a genome. The term "markers" often refers to polymorphisms, which are variations in DNA sequences that differ among individuals.

One common type of genetic marker is the single nucleotide polymorphism (SNP), which is a variation at a single nucleotide position in the DNA sequence. For instance, consider two individuals whose DNA sequences are nearly identical except for one nucleotide. In this case, if individual one has a thymine (T) at a specific position while individual two has a cytosine (C), this difference represents a SNP. Such variations are unique to each individual and can serve as identifiers, much like fingerprints.

A person's DNA fingerprint is essentially the combination of all their unique genetic markers, including various SNPs and other polymorphisms. This unique genetic profile can be used in various applications, such as forensic science, paternity testing, and genetic research, to accurately identify individuals based on their DNA.

As we delve deeper into the topic, we will explore practical applications and further examples of how DNA fingerprinting and genetic markers function in real-world scenarios.

Short tandem repeats, commonly abbreviated as STRs, are crucial genetic markers utilized in various fields, including forensic science. STRs consist of short sequences of DNA, typically ranging from 2 to 5 nucleotides long, that are repeated in specific regions of the genome. The number of these repeats can vary significantly among individuals, making them polymorphic and unique identifiers for each person.

For instance, in a given region of DNA, one individual may have five repeats of a specific sequence, while another may have only three, and yet another may have four. This variability allows researchers and forensic experts to distinguish between different individuals based on their DNA profiles. In practical applications, such as crime scene investigations, STR analysis can be instrumental in matching DNA samples found at a crime scene with those of potential suspects.

To illustrate, consider a repeated sequence like "GATA." If three individuals are analyzed, their DNA might show the following: Individual 1 has five GATA repeats, Individual 2 has three, and Individual 3 has four. This distinct pattern of STRs serves as a genetic fingerprint, enabling accurate identification.

In summary, STRs are vital for personal identification and have significant implications in forensic science, as they provide a reliable method for comparing DNA samples and solving crimes. As we continue to explore this topic, we will delve deeper into the applications and methodologies surrounding STR analysis.