| how do you determine the time of death of a mammal? | examine the extent of decomposition, stage of succession, forensic entomology, body temperature and the degree of muscle contraction |
| how can examining the extent of decomposition help determine the time of death? | bodies usually follow the same pattern of decay
bodies at certain stages of decay can be used to determine how long the body has been dead for |
| how can forensic entomology help determine the time of death? | study of insects
each species of insects have different life cycles
calculating the age of the insects present at the body can help determine the time of death |
| how does body temperature help determine the time of death? | the temperature of the body begins to decreases after death
exothermic reactions stop
can only be used for the first 24 hours
also depends on the surrounding conditions such as: size of the body, covering and weather conditions |
| how can degree of muscle contraction help determine time of death? | after death, muscles stiffen
ATP is used up and calcium ions build up in muscle cells
muscles are in a fixed state of contraction
this is rigor mortis
begins 2-4 hours after death and only lasts about 36 hours |
| what is the role of microorganisms in decomposition? | secrete enzymes that decompose organic matter
recycle the CO2 and CH4 produced using them as respiratory substrates
release nutrients trapped in the organic matter |
| what are the microorganisms involved in decomposition? | bacteria and fungi |
| define decomposition | the break down of larger and complex molecules into smaller simple molecules
can also be respiration |
| DNA profiling | also know as genetic fingerprinting
used to identify and determine genetic relationships between organisms (plants and animals) |
| what are introns? | non-coding regions found on DNA |
| what are exons? | coding region on DNA |
| PCR process | mix the DNA sample, primers, free nucleotides and DNA polymerase
heat to 95°C to break the hydrogen bonds and separate the two strands
cool to 50°C so that the primers can bind to the separated strands
heat to 70°C so that DNA polymerase creates a copy of the sample by complementary base pairing using the free nucleotides
leave the mix for about 1 min so the sample can be amplified
the cycle can be repeated so that there is enough DNA for a DNA profile |
| what are STR's? | short tandem repeats or satellites
repeating bases sequences
make up introns
are hypervariable |
| what is PCR and what does it do | polymerase chain reaction
amplifies DNA |
| gel electrophoresis process | DNA is cut into fragments by restriction endonucleases
the fragments are placed in wells and dye is added so it can glow in UV light
DNA is negative so when the current is turned on DNA moves to the anode (the positive electrode)
fragments of different sizes move at different speeds so bands of DNA will appear
the bands of each DNA sample will be compared to the pre-prepared DNA ladder |
| what is a primer? | single strands of DNA
defines the region of DNA that will be amplified |
| what is gel electrophoresis used for? | used to separate and visualise amplified DNA samples |
| what are restriction endonucleases? | enzymes
they cut up amplified DNA into fragments during gel electrophoresis |
