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Forensic Biology & DNA

The complete guide to forensic biology, body-fluid identification, hair and fibre microscopy, entomology, wildlife forensics, and the full DNA pipeline — for the NFSU FACT and UGC-NET Forensic Science exams.

Last updated 9 May 2026

Practice mocksFACT exam guide

What is forensic biology?

Forensic biology is the source-attribution arm of forensic science. Its job is to answer the who question: which person did this fluid come from, which species did this hair originate from, which animal did this bone belong to. The classical disciplines (serology, microscopy, entomology) have been joined since the 1980s by molecular biology, and DNA profiling has reshaped the field — but body-fluid identification, hair and fibre comparison, and species ID remain the foundations.

For an Indian forensic-science student the breadth matters. CFSL and state FSLs maintain biology divisions that handle sexual-assault casework (serology + DNA), homicide (post-mortem interval from entomology, identity from anthropology + DNA), and wildlife crime under the Wildlife Protection Act. Each stream has its own protocols, instruments, and reporting standards. The exam tests breadth more than depth — but you need both.

The eight syllabus units

FACT splits the biology section into eight units mapping to NFSU's MSc curriculum. The DNA-pipeline blocks are weighted heaviest, but every unit appears on every recent paper.

Body fluid identification

Presumptive and confirmatory tests for blood, semen, saliva, vaginal fluid and urine — the chain a serologist works through before a swab goes for DNA extraction.

Hair & fibre examination

Optical microscopy of class characteristics, plus instrumental confirmation (FTIR, Raman, polarised-light) for fibre polymer ID.

DNA extraction & quantitation

Sample-prep workflows (organic, Chelex, magnetic-bead) for blood / semen / bone / hair, plus qPCR-based quantitation before amplification.

STR profiling

Short-tandem-repeat amplification, capillary electrophoresis, allele calling, and the maths of match probability + likelihood ratio.

mtDNA & Y-STR

Mitochondrial sequencing for degraded samples and the maternal-line trace; Y-STR profiling for male-mixture deconvolution and paternal-line analyses.

Forensic entomology

Insect succession on a corpse and accumulated degree-days for post-mortem-interval estimation.

Wildlife forensics

CITES-listed species identification from hair, horn, ivory, scales, meat samples, and the law that backs Indian wildlife casework.

Forensic anthropology basics

Skeletal remains identification — sex, age, ancestry, stature — from bones and bone fragments.

Why forensic biology matters in entrance exams

Forensic biology is ~18–20 marks on a 100-question FACT paper. The DNA-pipeline questions are usually scenario-based: given this evidence type and degradation state, which extraction method, which quant kit, which marker system. The body-fluid unit tests presumptive-confirmatory chains. Hair / fibre questions are class-vs-individual recognition. Entomology questions reduce to ADD calculations or succession ID.

For UGC-NET Forensic Science the same pipeline appears with heavier theory loading — population-genetics calculations, paternity-index maths, mixture-deconvolution likelihood ratios, and history-of-the-discipline (Jeffreys 1985, Pitchfork case) questions. The instrumentation overlap is ~80% with FACT.

How to study — pattern

  1. Build the DNA pipeline mental model end to end: collection → extraction → quantitation → amplification → CE → analysis → match-probability stats. One sitting per stage.
  2. Drill body fluids. Memorise presumptive ↔ confirmatory pairs. Build a 1-page reference.
  3. Microscopy reference. Hair medulla patterns, fibre cross-sections, blowfly larval spiracles. Visual memory wins these questions.
  4. Topic mocks, one per sub-unit, in 20-minute sittings. Browse free mocks.
  5. Mistakes log + full-length mocks under exam conditions in the last month.

Sub-unit deep dives

1. Body fluid identification

Presumptive and confirmatory tests for blood, semen, saliva, vaginal fluid and urine — the chain a serologist works through before a swab goes for DNA extraction.

  • Blood: Kastle-Meyer (presumptive), Takayama / Teichmann (confirmatory crystal tests)
  • Semen: acid phosphatase + microscopic spermatozoa + p30 immunoassay
  • Saliva: alpha-amylase test (Phadebas / RSID-saliva)
  • Species determination: Ouchterlony (precipitin) or hemoglobin spectroscopy

2. Hair & fibre examination

Optical microscopy of class characteristics, plus instrumental confirmation (FTIR, Raman, polarised-light) for fibre polymer ID.

  • Hair: medulla pattern (continuous / interrupted / fragmented) → species ID
  • Cuticle scale pattern (imbricate / crenate / coronal) for animal hair
  • Fibre polymer ID: FTIR for synthetic; PLM for natural (cotton lumens, wool scales)
  • Cross-section morphology: round, dog-bone, trilobal, dumbbell — distinguishes manufacturer

3. DNA extraction & quantitation

Sample-prep workflows (organic, Chelex, magnetic-bead) for blood / semen / bone / hair, plus qPCR-based quantitation before amplification.

  • Organic (phenol-chloroform) — gold standard, most labour-intensive
  • Chelex 100 — fast, low-yield, single-tube — good for buccal swabs
  • Magnetic bead automation — current FBI / CFSL workflow standard
  • qPCR quantitation: Quantifiler / PowerQuant — sets up a target ng input for STR amplification

4. STR profiling

Short-tandem-repeat amplification, capillary electrophoresis, allele calling, and the maths of match probability + likelihood ratio.

  • CODIS 20-locus core (D3S1358, D5S818, vWA, FGA, ...) — one expanded from the original 13 in 2017
  • Multiplex PCR with fluorescent primers; CE separates by size + dye channel
  • Allele frequency × Hardy-Weinberg → random match probability
  • Stutter peaks (n-1 repeat artefact); minor-contributor thresholds in mixtures

5. mtDNA & Y-STR

Mitochondrial sequencing for degraded samples and the maternal-line trace; Y-STR profiling for male-mixture deconvolution and paternal-line analyses.

  • mtDNA: hypervariable regions HV1, HV2; Sanger or NGS sequencing
  • mtDNA inheritance — strictly maternal, no recombination → useful for missing-persons matching across generations
  • Y-STRs: Yfiler Plus 27 loci; haplotype frequency vs population
  • Y-STR limitation: all paternal-line males share a haplotype — exclusion-only, not unique ID

6. Forensic entomology

Insect succession on a corpse and accumulated degree-days for post-mortem-interval estimation.

  • Calliphoridae (blowflies) → Sarcophagidae → Dermestidae succession typical for India
  • ADD (accumulated degree days): integrates temperature × time → minimum PMI
  • Larval instar morphology (anterior + posterior spiracles) for species ID
  • Indoor vs outdoor scenes; coffin-fly succession variants

7. Wildlife forensics

CITES-listed species identification from hair, horn, ivory, scales, meat samples, and the law that backs Indian wildlife casework.

  • Indian Wildlife (Protection) Act 1972 schedules I–VI
  • Cytochrome b PCR sequencing — universal animal-species barcode
  • Hair / scale microscopy for tiger, leopard, pangolin
  • Bone / antler ID via SEM and morphological keys

8. Forensic anthropology basics

Skeletal remains identification — sex, age, ancestry, stature — from bones and bone fragments.

  • Sex from pelvis (sciatic notch, sub-pubic angle, ischiopubic index)
  • Age from cranial-suture closure, dental eruption, epiphyseal fusion
  • Stature from long-bone length (Trotter-Gleser regressions)
  • Cause-of-death indicators: blunt vs sharp vs ballistic trauma signatures
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Frequently asked questions

What is forensic biology?
Forensic biology applies biological sciences — body-fluid identification, hair / fibre examination, entomology, wildlife species identification, and DNA profiling — to legal investigations. It is the source-attribution arm of forensic science: where physical and chemical evidence answers "what," biology answers "who."
Is DNA profiling the whole subject?
No. DNA gets the headlines and ~50% of the FACT biology marks, but body-fluid identification, microscopy of hair / fibres, forensic entomology (post-mortem-interval estimation from blowfly succession), and CITES-listed wildlife species ID are all solid mark-share areas. A graduate-level forensic biologist needs all five competencies.
How much molecular biology is needed?
Working knowledge of PCR, capillary electrophoresis, and basic Mendelian inheritance covers most exam-level questions. You don't need to derive the chemistry of dideoxy-terminator sequencing — but you do need to know what an STR locus is, why CODIS uses 20 of them, and how to read an electropherogram.
When do you use mtDNA vs autosomal STRs?
Mitochondrial DNA when the sample is degraded (old bones, hair shafts without root) — ~1000 copies of mtDNA per cell vs 2 of nuclear DNA. Autosomal STRs are the default for fresh, nucleus-containing samples (blood, semen, tissue, saliva). Y-STRs are the right tool when you need to type the male contribution to a male/female mixture.
What's the FACT mark distribution like?
Forensic biology typically pulls 18–20 marks on the FACT paper, split roughly: DNA pipeline 9–10, body fluids 3–4, hair / fibres 2–3, entomology 1–2, wildlife 1–2. UGC-NET adds more population-genetics and case-law context.
Is BSc biology background required?
Most students taking FACT have a BSc in biology, biotech, microbiology, biochemistry, or a related life-science. BSc forensic-science programmes also feed in. The exam doesn't assume MSc-level molecular biology, but BSc-level genetics + cell biology + basic statistics is expected.