8 min readConcept sheetPart II (2 marks) on the uses of DNA fingerprinting; Part III (4 marks) or Part IV (7 marks) on the cloning of Dolly

DNA fingerprinting and cloning

DNA fingerprinting identifies a person from the unique pattern of repeat sequences in their DNA. Cloning makes a genetically identical copy, like Dolly the sheep.

DNA fingerprintingDeveloped by Alec Jeffreys (1984)

In IndiaLalji Singh, called the father of Indian DNA fingerprinting

DollyFirst mammal cloned from an adult body cell; born 5 July 1996, Roslin Institute, Scotland

Cloned byIan Wilmut and Keith Campbell

What is DNA fingerprinting?

Every person's DNA is unique, except for identical twins. Some parts of DNA have a short base sequence repeated many times. The number of repeats differs from person to person. These parts are called VNTRs (variable number tandem repeats). DNA fingerprinting compares these repeat patterns to identify a person. It was developed by Alec Jeffreys in 1984. In India, Lalji Singh developed it further, so he is called the father of Indian DNA fingerprinting.

Steps of DNA fingerprinting

1
Collect a sample: blood, a hair root, skin, saliva or semen.
2
Extract (isolate) the DNA from the cells.
3
Cut the DNA into pieces with restriction enzymes.
4
Separate the pieces by size with gel electrophoresis. An electric current moves DNA through a gel, and small pieces travel farther.
5
Transfer the pieces onto a nylon membrane. This is Southern blotting.
6
Add radioactive probes that stick only to the VNTR pieces.
7★
Place an X-ray film over it. A pattern of dark bands appears, like a bar code. This is the DNA fingerprint.

★ key step

Uses of DNA fingerprinting

Crime investigation: matching DNA from blood or hair at a crime scene with a suspect's DNA.
Settling paternity (parentage) disputes.
Identifying bodies after accidents, fires or disasters.
Studying family histories, human migration and evolution.
Identifying animals and plants, as in wildlife smuggling cases.

How to draw the flow chart: cloning of Dolly

**Cloning** means making a genetically identical copy (a clone) of a cell, gene or whole organism. Dolly was made by **somatic cell nuclear transfer**: the nucleus of a body cell was put into an egg whose own nucleus was removed. Draw each box, join them with arrows and write the labels.

Merits and demerits of cloning

MeritsCopies of high-yielding farm animals. A way to save endangered species. Stem cells for research and treatment (therapeutic cloning). Many copies of useful genes (gene cloning).

DemeritsVery low success rate. Clones may fall ill or age early: Dolly had lung disease and lived only until 2003. Less genetic variety, so one disease can harm all. Serious ethical questions.

Copying a whole human being by cloning is not allowed in many countries.

In real life

Indian courts accept DNA evidence in crime and parentage cases. Banana, sugarcane and potato plants grown from suckers, cuttings or tubers are natural clones of the parent plant.

Exam angle

1 marks: “Who is called the father of Indian DNA fingerprinting?” Lalji Singh.

2 marks: “Write any two uses of DNA fingerprinting.” Identifying criminals from crime-scene samples; settling paternity disputes; identifying bodies after disasters.

7 marks: “What is cloning? Explain how Dolly was cloned, with a flow chart.” Definition; Wilmut and Campbell, Roslin Institute, 1996; udder cell nucleus (Finn Dorset) + enucleated egg (Scottish Blackface), electric fusion, embryo into surrogate; Dolly identical to Finn Dorset; merits and demerits.

Remember it

Dolly = Dorset's DNA, in a Blackface egg, born from a Blackface womb.