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level: Forensics

Questions and Answers List

level questions: Forensics

QuestionAnswer
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 decompositionthe break down of larger and complex molecules into smaller simple molecules can also be respiration
DNA profilingalso 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 processmix 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 dopolymerase chain reaction amplifies DNA
gel electrophoresis processDNA 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