T ECHNIQUES OF DNA A NALYSIS Josh Maniez CJ 210 6/12/15

DNA A NALYSIS DNA analysis is an examination method that started in the 1980’s by Alec Jefferys. It works by examining DNA sequences unique to a specific species. Forensic scientists examine 13 DNA regions and create a DNA profile for an individual with finger prints. This analysis can be used in forensics to link evidence to a suspect, exonerate a person that is wrongly charged with a crime, and find paternity relationships. DNA can be collected from weapons, hats, facial tissue, cigarettes, bottles, used condoms, bed linens, or finger nails.

RESTRICTION FRAGMENT LENGTH POLYMORPHISM Restriction fragment length polymorphism is a technique that is not so much popular now but it was one of the first techniques used years ago. It looks for differences between homologous DNA molecules being different from other restriction enzyme sites. The DNA is broken into pieces by enzymes and restriction fragments separate by gel electrophoresis. This type of analysis is useful for genome mapping, determining risks of disease, genetic disorders, and paternity testing. The downfall is that large sample sizes are needed and the process can take up to a moth compared to newer techniques that only need a few cells.

VARIABLE NUMBER TANDEM REPEATS Variable number tandem repeats are a vital part of restriction fragment length polymorphism used in mapping of diploid genomes. This is essential for forensic crime investigations because it helps with fingerprinting and the CODIS database. Gel electrophoresis determines the sample size and they create patterns of bands that are different from one another. Two major uses from this method are identity matching and inheritance matching. Identity matching is when both alleles form a certain location match or if more than one sample is collected from the same person, they must match. Inheritance matching is when a person must have a matching allele from each parent or possibly matching with a sibling can show matches.

SHORT TANDEM REPEAT ANALYSIS Short tandem repeat analysis studies individual areas in DNA. It compares the differences of one person’s DNA to another to distinguish between people. This is a good technique used in criminal investigations that analyzes thirteen regions to find a matching profile. This method has become one of primary uses of DNA analysis by helping create criminal DNA databases. Also, it is commonly used for finding a missing person, paternity testing, and disaster investigations.

Y-C HROMOSOME A NALYSIS Y-chromosome analysis looks at genetic markers on a Y chromosome that passes from a father to his son. This method creates an understanding of a family tree over several generations and is used in forensic laboratories to find sexual assault evidence. They would conduct a vaginal swab that will contain the female and male’s DNA. Also, this technique is used in non-sexual assault cases when mixed samples are found from evidence but sometimes the female DNA has a masking effect on the male’s DNA which makes it hard to show up.

M ITOCHONDRIAL DNA A NALYSIS Also, Mitochondrial DNA analysis plays a big factor on DNA samples that are unable to be analyzed by restriction fragment length polymorphisms or short tandem repeats. Most DNA analysis methods remove the nuclear DNA in the cell but mitochondrial DNA analysis removes the DNA from the cell’s mitochondria. This is relied on when the sample is old and no longer has nuclear material which is great for identify a missing person and making DNA profiles.

C OLLECTING AND P RESERVING DNA E VIDENCE DNA evidence must be able to be collected properly to avoid viruses and germs contaminating the sample that would make it useless. The sample needs to stay dry and free of moisture by storing it at room temperature. A sample is usually put inside of a bag or envelope that is sealed with a label so it can be monitored.