explain the steps of DNA fingerprints that eill help in processing of the two blood samples A and B picked up from the crime scene
Answers
DNA fingerprinting is a method used to identify an individual from a sample of DNA by looking at unique patterns in their DNA.
Background
Almost every cell? in our body contains our DNA?.
On average, about 99.9 per cent of the DNA between two humans is the same.
The remaining percentage is what makes us unique (unless you are an identical twin!).
Although this might sound like a small amount, it means that there are around three million base pairs? that are different between two people. These differences can be compared and used to help distinguish you from someone else.
Minisatellites are short sequences (10-60 base pairs long) of repetitive DNA that show greater variation? from one person to the next than other parts of the genome?. This variation is exhibited in the number of repeated units or ‘stutters’ in the minisatellite sequence.
The first minisatellite was discovered in 1980.
DNA fingerprinting
DNA fingerprinting was invented in 1984 by Professor Sir Alec Jeffreys after he realised you could detect variations in human DNA, in the form of these minisatellites.
DNA fingerprinting is a technique that simultaneously detects lots of minisatellites in the genome to produce a pattern unique to an individual. This is a DNA fingerprint.
The probability of having two people with the same DNA fingerprint that are not identical twins is very small.
Just like your actual fingerprint, your DNA fingerprint is something you are born with, it is unique to you.
How was the first DNA fingerprint produced?
The first step of DNA fingerprinting was to extract DNA from a sample of human material, usually blood.
Molecular ‘scissors’, called restriction enzymes?, were used to cut the DNA. This resulted in thousands of pieces of DNA with a variety of different lengths.
These pieces of DNA were then separated according to size by a process called gel electrophoresis?:
The DNA was loaded into wells at one end of a porous gel, which acted a bit like a sieve.
An electric current was applied which pulled the negatively-charged DNA through the gel.
The shorter pieces of DNA moved through the gel easiest and therefore fastest. It is more difficult for the longer pieces of DNA to move through the gel so they travelled slower.
As a result, by the time the electric current was switched off, the DNA pieces had been separated in order of size. The smallest DNA molecules were furthest away from where the original sample was loaded on to the gel.
Once the DNA had been sorted, the pieces of DNA were transferred or ‘blotted’ out of the fragile gel on to a robust piece of nylon membrane and then ‘unzipped’ to produce single strands of DNA.
Next the nylon membrane was incubated with radioactive probes.
Probes are small fragments of minisatellite DNA tagged with radioactive phosphorous.
The probes only attach to the pieces of DNA that they are complementary? to – in this case they attach to the minisatellites in the genome.
The minisatellites that the probes have attached to were then visualised by exposing the nylon membrane to X-ray film.
When exposed to radioactivity a pattern of more than 30 dark bands appeared on the film where the labelled DNA was. This pattern was the DNA fingerprint.
To compare two or more different DNA fingerprints the different DNA samples were run side-by-side on the same electrophoresis gel.
Answer:
DNA fingerprinting is also known as DNA profiling. This is the method which is used to identify the criminals and suspects. There are many steps involved in DNA fingerprinting. The first step is isolating the desired DNA which can be performed chemically, mechanically or enzymatically. The second step is cutting the DNA into several pieces by restriction enzymes. The third step is sorting the DNA pieces by gel electrophoresis. The DNA will be separated by size. The next step is denaturing the DNA fragments. The next step is blotting the DNA The gel with the size-fractionated DNA is applied to a sheet of nitrocellulose paper or nylon membrane. In order to analyze a Southern Blot, a radioactive genetic probe is used in a hybridization reaction with the DNA. The X-ray film helps to analyse the fragments.
Explanation:
please mark me brainliest