Forensic investigation and analysis of DNA Flashcards
Why is temperature data important when determining time of death
- insects rate of growth/life cycles is faster with high temperatures
- it is temperature dependent
- rate is fixed at constant temperature
- weather conditions affect temperature of room
Why collecting several species of insect would make estimate of time of death more reliable
- several values for development rate
Why a scientist cannot be precise as to the time of death
- do not know temperature throughout (temp not constant)
- so rate might vary
- might have died at night, so infestation next morning
- insects difficult to enter room
- too late for other evidence
Does DNA fingerprinting provide enough evidence
- DNA doesn’t change
- DNA unique to individual
- DNA fingerprinting is reliable
Example of physical evidence that could be retained and why sample is suitable for a DNA test to be carried out
- tissue
- tissue cells contains intact DNA
Explain how the results of DNA fingerprinting could be used to find the identity of a dead person
- sample from corpse
- match with family
- match with a previous sample
How succession accounts for the changes in the types of organisms found on the body
- succession is changes of organisms with time in a predictable order
- early colonisers change conditions for other organisms to colonise
- conditions now better suited for later groups
- competition occurs
Describe how a key could be used to identify the organism on the body
- characteristics compared
- examples of characteristics
- larvae develop into adults
- magnification
- description of questions
Explain why estimation of time of death may be inaccurate
- no record of environmental conditions
- temperature may vary
- temperature affects development of insects
- rate of development varies
- time taken to lay eggs varies, delay before finding corpse, e.g. died at night
Enzyme used to amplify the DNA in PCR
- DNA polymerase
Process that could be used to separate DNA fragments to create a DNA profile
- gel electrophoresis
Suggest which is most likely a suspect with reference to theory used in DNA profiling
- all bands matches
- DNA profiling assumes individuals’s DNA is unique, apart from identical twins- DNA profiling analyses STR’s within introns (non-coding blocks)
- non-coding DNA is very variable
- large number of introns
- many different combinations at each locus
Explain why evidence from DNA profiles may not be absolutely conclusive
- DNA profiling has several stages
- contamination can arise at any stage
- only a small portion of DNA analysed
- possibility of two identical profiles from unrelated individuals
- closely related individuals may show same profile
Suggest how DNA profiling could be useful to scientists who examine fossils of animals and plants
- comparisons made between DNA and from fossils and other organisms
- to find genetic relationships
- used for taxonomy (classification)
- to determine a common ancestor
Explain how CO2 and ammonia are formed during the putrefaction stage of decomposition
- microorganisms respire aerobically
- converts organic compounds to CO2
- converts nitrogen compounds into ammonia
