What is DNA?
- DNA (Deoxyribonucleic Acid) is the hereditary material found in almost all human cells – blood, skin, bone, teeth, etc.
- Humans have 46 chromosomes:
- 23 inherited from the father (via sperm)
- 23 inherited from the mother (via egg)
- Genes within chromosomes determine physical traits and biological identity.
DNA Polymorphisms
- DNA polymorphisms are variations in DNA sequences unique to individuals.
- Useful for:
- Parentage identification
- Genetic lineage tracing
- Identity verification in Forensic Science
- Enable accurate matching between body samples and known relatives.
Short Tandem Repeats (STRs)
- STRs are short, repeating sequences of DNA bases (e.g., GATCGATC).
- Each individual has a unique STR pattern, making them ideal for:
- Criminal investigations
- Forensic victim identification
- Ancestry and paternity testing
- STRs are inherited, providing strong evidence for genetic relationships.
Polymerase Chain Reaction (PCR) in DNA Amplification
- PCR is a technique to amplify small amounts of DNA for analysis.
- Steps involved:
- DNA Extraction from bones, blood, or tissue
- Denaturation (95°C): DNA strands are separated
- Annealing (60°C): Primers bind to specific DNA sequences
- Extension (72°C): DNA polymerase builds new strands
- Cycling: Steps are repeated to create millions of DNA copies
DNA Fingerprinting
- A DNA fingerprinting is a unique genetic profile built using STR variations.
- Capillary Electrophoresis separates STR fragments based on size using electric current.
- Final output is a distinct DNA profile, unique to each person (except identical twins).
- Sources for DNA: blood, saliva, bone, teeth, skin cells, sweat, semen.
