Explain the role of DNA primers in the production of the amplified 345bp sequence. (2)
- primers have a specific base sequence
which bind to complimentary bases of the amplified DNA - therefore a site for DNA polymerase to bind
Explain why the amplified DNA fragments for the G20210A allele and the wild type allele are different. (3)
- base sequence of the alleles are different
- therefore restriction enzyme cuts at specific DNA base seq which is found specifically on G20210A
- therefore a shorter fragment produced
Devise an investigation to determine optimum number of cycles for polymerase chain reaction used to amplify DNA for this test. (4)
- heat mixture to around 95° to break hydrogen bonds b/w DNA strands
- mixture cooled to 60° so primer can anneal
- use gel electrophoresis to determine quantity of DNA produced
Comment on effect of adding cow dung to composting coffee husks. (3)
- start of composting: % of organic carbon is lower, % of nitrogen is higher
- adding cow dung does not effect organic carbon
- but causes slight change to nitrogen %
Describe how this study could be carried out. (pigs)
- control: size and breed of pigs
& temp - record types of different insects which colonise body every hour
Explain how results of this study (pigs) could be used to help establish time of death of a human. (3)
- by looking at life cycle of organism that is present and recording the types
- compare the results with the results from the time of death of pigs
Describe how DNA profiling could be carried out to show that these snakes are diff species. (4)
- DNA samples from diff types of grass snakes taken and amplified using PCR
- DNA fragments separated by length
- larger fragments slower than shorter
- UV light reveals the different bands which can be compared to show that they are different species
Describe how one PCR cycle would increase DNA quantity. (3)
- heat to 95: separates DNA strands
- annealing at 60
^ doubles quant. of DNA
Explain how microorganisms in soil break down stems. (3)
- stem contains starch
- enzymes secreted by microorganism
^ break down glycosidic bonds
Explain effect of ambient temp on decomposition rate. (3)
- increased temp = increased decomposition rate
& increased enzyme activity
& increased growth rate of decomposers
Explain how gel electrophoresis can be used to find out if the DNA is from a black panther. (5)
- current applied across gel
- use DNA stain
- also use DNA of black panther
- compare bands
- match indicated that black panther is present
Devise a procedure to compare amplified DNA from these two human types. (4)
- restriction enzymes used to cut DNA into fragments
- DNA samples loaded into agarose gel
- electric current passed through gel
- position of bands produced can be compared
Describe the role of decomposers in the carbon cycle. (2)
- break down organic materials
- respire, releasing CO2 into atmosphere
Describe the changes that occur inside the body in the first week after death. (3)
- body temp. falls
- rigor mortis
- breakdown of tissues by enzymes
