DNA Fingerprinting | Genetics | Biology | FuseSchool

Summary

DNA fingerprinting, developed by Alec Jeffries in 1985, is a technique used to compare DNA samples for identifying criminals and confirming familial relationships. By analyzing short tandem repeats (STRs) in DNA, which vary between individuals, this sensitive process can work with small amounts of biological material like blood or saliva. DNA profiling involves extracting DNA, amplifying it with PCR, and separating it through gel electrophoresis. It's then compared across samples, such as in crime scene investigations or paternity tests, providing critical evidence for solving mysteries and identifying individuals.

Takeaways

• 😀 DNA fingerprinting, or DNA profiling, was developed by geneticist Alec Jeffries in 1985 at Leicester University.
• 😀 DNA fingerprinting allows DNA samples from different people to be compared for similarities and differences, helping solve crimes and confirm relationships like paternity.
• 😀 99.9% of human DNA is the same across all individuals, and DNA fingerprinting analyzes the remaining 0.1% for unique differences.
• 😀 The process of DNA profiling focuses on short tandem repeats (STRs), which are repeated sequences of bases in the DNA that vary in length among individuals.
• 😀 A small sample of DNA, such as from skin cells, hair roots, or a drop of blood, can be used for DNA profiling due to the sensitivity of the technique.
• 😀 DNA samples are processed using polymerase chain reaction (PCR) to create many copies before restriction endonucleases cut them into different-sized pieces.
• 😀 Gel electrophoresis separates the DNA fragments by size, creating a pattern that can be visualized and compared between samples.
• 😀 The DNA pattern is transferred to a nylon sheet through Southern blotting, where the bands from different individuals can be compared.
• 😀 In crime scene investigations, DNA samples from suspects are compared with those found at the crime scene to identify the perpetrator.
• 😀 DNA profiling can also be used to identify family relationships, such as determining which set of parents a soldier lost in battle belongs to based on shared DNA patterns.

Q & A

What is DNA fingerprinting and who developed it?

DNA fingerprinting, also known as DNA profiling, is a technique developed by Leicester University geneticist Alec Jeffries in 1985. It allows DNA samples from different people to be compared, identifying similarities and differences.

What is the purpose of DNA fingerprinting?

DNA fingerprinting is used for solving crimes and can also confirm familial relationships, such as in paternity testing.

How similar is the DNA of any two people?

Any two people in the world share 99.9% of their DNA, with the remaining 0.1% being analyzed for differences in DNA profiling.

What are short tandem repeats (STRs) and why are they important in DNA profiling?

Short tandem repeats (STRs) are regions of DNA where short sequences of bases, like three, four, or five bases, are repeated multiple times. These repeated sequences vary in the number of repeats between individuals, making them useful for DNA profiling.

What types of biological samples can be used for DNA fingerprinting?

DNA samples for fingerprinting can be obtained from various sources, including skin cells, hair roots, blood, or saliva.

What is the role of polymerase chain reaction (PCR) in DNA fingerprinting?

Polymerase chain reaction (PCR) is used to make many copies of the DNA extracted from the sample, which is crucial for DNA profiling.

How does gel electrophoresis work in DNA fingerprinting?

In gel electrophoresis, DNA fragments are placed in wells of an agarose gel, and an electric current is applied. This separates the DNA fragments by size, with smaller fragments moving faster than larger ones.

What is Southern blotting and what is its purpose in DNA profiling?

Southern blotting is a technique used to transfer the separated DNA fragments from the gel onto a nylon sheet, where they can then be analyzed to create a DNA profile.

In the DNA profiling example with the burglary, how do you determine the guilty suspect?

The guilty suspect can be identified by comparing the DNA profile from the crime scene with the DNA samples from the suspects. The suspect whose DNA pattern most closely matches the one from the crime scene is the guilty party.

How can DNA profiling be used to identify a soldier's parents?

In the case of a missing soldier, DNA samples from the soldier’s parents can be compared to the soldier's DNA. Since a child inherits half of their DNA from each parent, the comparison can help identify which set of parents the soldier belongs to.