DNA profiling: method and uses
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Explainer Video
Summary
DNA profiling: method and uses
In a nutshell
DNA profiling is widely used in forensic science and medical diagnosis. DNA profiling focuses on tandem repeats, which are repeated segments of DNA that do not code for proteins.
Tandem repeats
Definition
Tandem repeats are repetitive segments of non-coding DNA. They are usually made up of bases and they are repeated a different number of times in different people.
Short tandem repeats (STRs) are highly variable and are around bases long. Usually, STRs are analysed at the same time. Each STR is present in between of individuals. However, the chances of two people sharing every STR analysed is one in a quintillion ( ).
Example
A repeated motif could be ATAG and this could be repeated four times in an individual. Therefore, a section of their DNA sequence would read ATAGATAGATAGATAG. Another individual may have seven repeats of the motif. This can therefore be used to distinguish between people.
Making a DNA profile
| 1. | Collect a DNA sample and isolate the DNA. ExampleDNA can be collected from blood, skin cells and saliva. |
| 2. | Using appropriate primers and PCR, amplify the section of DNA containing the STRs. |
| 3. | Run the PCR products on an electrophoresis gel. |
| 4. | Compare the banding patterns. |
Example
A DNA profile was constructed from DNA found at a crime scene (CS). DNA from three suspects was taken. Suspect 2. has the same banding pattern to the crime scene profile. The number and location of the bands is the same. Therefore, suspect 2. is guilty.
Uses of DNA profiling
Use | Explanation |
| Forensic science | DNA profiling is commonly used during criminal cases to match suspects to DNA obtained from crime scenes. |
| Maternity and paternity profiling | DNA profiling can be used in maternity and paternity testing as half of a child's genetic information derives from each of their parents. |
| Plant and animal breeding | Plants or animals with a particular allele of a desirable gene can be used for breeding to increase the probability of their offspring having the desired characteristic. |
FAQs - Frequently Asked Questions
How is DNA profiling used in forensic science?
DNA profiling is commonly used during criminal cases to match suspects to DNA obtained from crime scenes.
What are tandem repeats?
Tandem repeats are repetitive segments of non-coding DNA.
What is a use of DNA profiling?
DNA profiling can be used in maternity and paternity testing as half of a child's genetic information derives from each of their parents.
What are possible sources of DNA?
Possible sources of DNA are blood, skin cells and saliva.