Definitions [1]
Definition: DNA Fingerprinting
The technique of identifying an individual by analyzing the unique DNA sequence present in each person, similar to fingerprints, is called DNA fingerprinting.
Key Points
Key Points: The Lac Operon
- The operon model, proposed by Jacob and Monod (1961), explains coordinated regulation of gene expression in prokaryotes at the transcriptional level.
- An operon consists of a promoter, operator, and a group of structural genes that are regulated together and transcribed as a single polycistronic mRNA.
- In the lac operon of E. coli, three structural genes—z (β-galactosidase), y (permease), and a (transacetylase)—are involved in lactose metabolism.
- The regulator gene (lac i) produces a repressor protein that binds to the operator and prevents transcription in the absence of lactose.
- When lactose is present, it inactivates the repressor, allowing RNA polymerase to transcribe the structural genes (induction).
- Catabolite repression occurs when glucose is present; lac operon expression is suppressed and later activated by CAP–cAMP when glucose is depleted.
Key Points: Human Genome Project
- The Human Genome Project (HGP) was proposed in 1986 to map and sequence the entire human genome.
- It was an international effort involving about 100 laboratories from nearly 18 countries.
- The main goals included identifying all human genes, sequencing three billion base pairs, and storing data in databases.
- Two major approaches were used: Expressed Sequence Tags (ESTs) and whole genome sequencing with annotation.
- DNA fragments were cloned using BAC and YAC vectors in bacteria and yeast for sequencing.
- The human genome contains about 3.2 billion nucleotide bases and approximately 20,000–30,000 genes.
- Less than 2% of the genome codes for proteins, while repetitive DNA forms a large portion.
- About 99.9% of DNA sequences are identical among all humans; variations include SNPs and CNVs.
- HGP has applications in disease diagnosis, genetic counselling, gene therapy, and understanding human evolution.
- Ethical concerns include misuse of genetic data for discrimination, insurance denial, and attempts at genetic manipulation.
Key Points: DNA Fingerprinting
- DNA fingerprinting is a technique used to identify individuals based on unique patterns in their DNA sequences.
- It is based on repetitive DNA sequences called VNTRs (Variable Number Tandem Repeats), which show high polymorphism among individuals.
- These repetitive sequences are part of satellite DNA, including minisatellites and microsatellites.
- The technique was developed by Alec Jeffreys, and even a very small DNA sample can be used.
- The main steps include DNA extraction, PCR amplification, restriction digestion, gel electrophoresis, Southern blotting, hybridisation, and autoradiography.
- The resulting banding pattern is unique for each individual, except in identical (monozygotic) twins.
- DNA fingerprinting is widely used in forensic science, paternity testing, and personal identification.
- It is also useful in studying genetic diversity, population structure, and diagnosing certain inherited diseases.
