DNA Profiling - stages
- tissue sample obtained + DNA extracted
- (not enough DNA - PCR)
- fragments of different lengths created but cutting up DNA
- fragments separated and visualised
- DNA profile compared w/ another
Obtaining DNA - process
- tissue sample broken down in buffer solution to disrupt membranes
- filtering/ centrifuging - small suspended particles separated
- protease added - removes proteins
- cold ethanol added to precipitate out DNA
Polymerase Chain Reaction - process
- DNA sample placed in reaction tube w/ DNA polymerase, DNA primers and nucleotides
- cycle of temperature changes
- 95 - separate DNA strands
- 55 - primers attach at start of STR
- 70 - DNA adjacent replicated
Creating DNA Fragments - process
- add restriction enzymes (endonucleus)
- recognise specific DNA sequence
- cuts section out
Separating DNA Fragments - process
Gel Electrophoresis
- DNA placed in arose in buffer
- connected to electrodes
- neg charged fragments migrate through gel
Visualising Fragments - how?
Southern Blotting
Uses of DNA Profiling
- identification
- paternity disputes
- evolutionary relationships
Time of Death - stages
- Temperature
- Degree of Rigor Mortis
- State of Decomposition
- Entomological Evidence - insects
- Stage of Succesion
Temperature - death
- cools due to lack of chemical reactions
- rate varies due to , body size/position, clothing, in water
Rigor Mortis - process
- muscles starved of O2 - anaerobic resp - lactic acid
- pH cell falls - inhibiting enzymes
- ATP production stops + bonds btwn muscle proteins fix
- muscles can’t contract or relax - become fixed
Decomposition - time of death
- autolysis occurs (enzymes break down tissues)
- bacteria from gut and gas exchange system invade tissue
- anaerobic bacteria grow
Signs of Decomposition
- greenish lower abdomen
- gas/liquid blisters on skin
- body bloated + smelly
Forensic Entomology
- take samples of insects in/around the body
- see what stage of growth/ development they’re in
Succession on Corpses
- different insects colonise the body at different times
- can also determine if body been moved
Humoral Response – process
- antigen presenting cell produced (phagocytosis)
- T-helper cell binds to APC and releases cytokine
- B-cell (which has already bound to antigen) activated
- proliferation
- memory cells and B-effector/ plasma cells produced
- plasma cells produce non-cell bound antibodies and so destroy complementary antigens
Cell Mediated Response – process
- antigen presenting cell produced (phagocytosis)
- T-helper cell binds to APC and releases cytokine
- T-cell (which has already bound to antigen) activated
- proliferation
- T-memory and T-killer cells produced
- T-killer cells cause lysis to occur in any cells carrying specific antigen
HIV attacking T-helper cells
HIV binds w/ CD4 receptors on T-helper cell and then fuses with it - its RNA then enters the cell
HIV replication in T-helper cell - process
- Reverse normal transcription and make DNA from RNA template (use reverse transcriptase)
- HIV DNA strand integrated into hosts DNA by HIV enzyme integrase
- It can then be transcribes + translated to make new virus proteins
AIDS - phases
- ACUTE phase
- HIV antibodies appear in blood (3-12 weeks)
- flue like symptoms
- rapid replication of hiv and loss of T-helper cells
- CHRONIC phase
- no symptoms - however easily infected by other illnesses - DISEASE PHASE
- very low no. T-helper cells
- high chance of opportunistic infections
Types of Antibiotic
BACTERIOCIDAL - kill bacteria
BACTERIOSTATIC - prevent multiplication then destroyed
Ways antibiotics disrupt bacteria growth (5)
- inhibition of cell wall synthesis = lysis
- disruption of cell membranes = lysis
- inhibition of nucleic acid synthesis, replication and translation = prevents division/ synthesis of enzymes
- inhibition of protein synthesis = essencial proteins not produced
- inhibition of specific enzymes found in bac cell
