T6 Forensics Flashcards
An investigation was carried out to study the rate of decomposition of leaves from ash trees
and beech trees.
Five piles of each type of leaf were placed outside on the ground and each pile was covered with
a heavy bucket. Each pile of leaves had a mass of 10 grams.
Every few weeks, one pile of each type of leaf was removed and weighed.
Explain why there is a decrease in mass of the leaves.
(4)
- Bacteria/fungi/decomposers release enzymes for decomposition.
- Formation of glucose/amino acids/small molecules.
- That are soluble/dissolve.
- Some soluble molecules soak into the ground/taken up by organisms.
- Respiration of glucose by decomposers.
- Carbon dioxide released.
- Water loss.
- Animals eat the leaves.
Suggest what effect an increase in temperature would have on the rate of decomposition of
these leaves. Give an explanation for your answer.
(4)
- Increase in temperature would increase the rate of decomposition to an optimum temperature.
- Enzymes involved in decomposition.
- Increased heat increases kinetic energy resulting in an increased number of collisions between enzymes and substrate. More enzyme substrate complexes.
- Increased temperature increases rate at which bacteria increase.
- Above certain temperature rate of decomposition would decrease.
- At higher temperatures enzymes become denatured and bacteria killed.
One method of estimating the time of death is to determine the age of blowfly maggots on a
dead body.
Microorganisms are also found on a dead body.
Describe the role of decomposers, such as microorganisms, in the carbon cycle.
(2)
- Decomposers break down organic material from dead body.
- Decomposers respire.
- Releasing carbon dioxide into the atmosphere.
A small sample of DNA was taken from each species of grey tree frog. This DNA was amplified,
fragmented and used to produce a DNA profile (DNA fingerprint) for each species.
*(i) Describe how a DNA profile was produced from this small sample of DNA.
(6)
- Multiple copies of DNA made using polymerase chain reaction.
- Using primers/DNA nucleotides.
- Restriction enzymes to produce DNA fragments.
- Or using gel electrophoresis.
- Loading DNA onto agar gel.
- Electric current/charge/potential difference applied.
- Then use of southern blotting/gene probes.
Suggest how these DNA profiles were compared.
3
- Comparing total number of bands.
- Comparing position of bands.
- Comparing size/width of bands.
Scientists in different parts of the USA are investigating the possibility that the difference in
cell size is responsible for the different mating calls. This is contributing to an understanding of
the evolution of grey tree frogs.
Suggest two ways in which the results of their investigations can be shared.
(2)
- Peer review.
- Scientific conferences/lectures.
- Media reports i.e. TV, radio, newspaper.
A deer was found dead on National Trust land. Some people thought that the wounds that led to
the deer’s death could have been caused by a big cat such as a black panther.
The DNA produced by PCR was analysed to find out if a black panther was involved.
Explain how gel electrophoresis could be used to find out if this DNA came from a black panther.
(5)
- Use of gel electrophoresis loading DNA onto agarose gel.
- Current/potential difference applied across gel.
- Use of gene probe/DNA stain.
- Use of STR’s/DNA of black panther.
- Compare bands/DNA profiles.
- A match would indicate DNA from a black panther was present.
Explain why recording rectal temperature is more reliable than measuring skin temperature.
(2)
-Rectal temperature is core temperature/ would be 37 degrees at time of death.
-Skin surface temperature more variable.
-
In addition to body temperature, forensic scientists would look for other evidence of time of
death.
Give two other pieces of evidence from a body that allow for an estimation of the time of death.
(2)
- Rigor mortis.
- Degree od decomposition.
- Entomology.
Researchers carried out a study on the prey of predatory ground beetles. They removed the
contents of the guts of beetles which had been feeding and analysed them to see if they could
identify the species they had fed on.
In one study, to see if the method worked, they fed the beetles on earthworms of the species
Allolobophora chlorotica only.
DNA was extracted from the gut contents and analysed.
(a) The quantity of worm DNA in the beetle gut was very small.
Describe how sufficient DNA was produced to carry out the analysis.
(3)
- PCR using primers/DNA polymerase/nucleotides.
- Procedure repeated multiple times/20-40 times.
- Temperature requirements to denature and anneal.
