Question

(a) The steps in DNA fingerprinting are given. Complete the flowchart (A & B).

(b) Mention the applications of DNA fingerprinting.

Answer 1

Hint: DNA fingerprinting or DNA profiling is a process used for determining the nucleotide sequence of a certain part of the DNA that is unique to an individual in a population.
The second step of DNA printing involves molecular scissors. The second last step before the detection step through autoradiography in order to analyze a Southern Blot, a detecting entity is used to bind with the DNA of interest.

Complete step by step answer:
(a) The steps involved in DNA fingerprinting are as follows:
- Isolation of the DNA from cells is the very first step required to extract the gene of interest.
- Cutting up the DNA using a restriction enzyme (A in the figure) to cut out the gene of interest from the rest of the DNA.
- Separation of DNA fragments by electrophoresis is carried according to their different sizes with respect to the molecular ladder.
- Transferring of the DNA to synthetic membrane: Here, the DNA fragments are permanently fixed in the nylon membrane from the gel.
- The next step (B in the figure) is to select our gene of interest which is achieved by using a radioactive probe complementary to the gene of interest.
- In the end, with the help of autoradiography, the hybrid of DNA- Radioactive Probe is detected.
(b) The applications of DNA Fingerprinting are:
- Forensic Science: Biological materials are used for DNA profiling such as blood, hair, saliva, semen, body tissue cells, etc. DNA isolated from the evidence sample at the crime scene can be compared through the VNTR (Variable number of tandem repeats) prototype of the suspects. It is useful in solving cases involving murder and rape.
- Paternity and Maternity Determination: A person inherits his or her VNTRs from his or her parents. Parent- child VNTR prototype analysis could be used to solve disputed cases.
- Personal Identification: This utilizes the concept of using DNA fingerprints as a sort of genetic barcode unique to each individual thus, helping to pinpoint individuals.
- Diagnosis of Inherited Disorders: It is also useful in diagnosing inherited genetic disorders in both prenatal and newborn babies. These disorders are such as cystic fibrosis, hemophilia, Huntington’s disease, sickle cell anemia, thalassemia, etc.
- Breeding Program: Using DNA fingerprinting breeders usually try to evaluate the genotype of a plant or an animal to make out the homozygous or heterozygous dominance in a population.

Note:
- Before the hybridization process the DNA fragments are cross- linked with the nylon membrane using U.V radiation for nanoseconds.
- After hybridization, wash buffers are used to clear away the rest of the unhybridized fragments to reduce the background noise during autoradiography.