| Date | May 2016 | Marks available | 2 | Reference code | 16M.3.HL.TZ0.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
International agreement limits the hunting of whales. Only the meat of the Minke, Fin and Humpback whales from Southern Hemisphere populations is allowed to be sold on the domestic market in Japan. Scientists obtained five samples of food that were being sold as “whale meat” in a Japanese market place. They identified the species and probable geographic origin of the meat using genetic analysis. The results were used to construct the cladogram.
Using the data in the cladogram, state the reason for sale of Sample 1 meat being illegal in Japan.
Using the data in the cladogram, state the reason for sale of Sample 4 meat being illegal in Japan.
Outline how the polymerase chain reaction (PCR) might have been used in this study.
Explain how sequence alignment software might have been used in this study.
Markscheme
It is from a North Atlantic population
It is from dolphin/species that is not on the list
Collected DNA sample is small/too minute to study
DNA from tissue sample amplified «by PCR»
OR
Obtain increased yields/quantities of specific DNA sequences
Test primers «from legal species» are used
Example of genes used «to construct test primers» eg: 18S ribosome, cytochrome C oxidase
If no amplification occurs, then test is negative
Sequence a sample of DNA/protein from the tissue
Run a BLAST/sequences alignment software search for similar sequences «of DNA/protein»
A match can be used for species identification
OR
Percentage similarity of sequences used to build up cladogram
BLASTp is used if protein sequenced AND BLASTn if DNA sequenced (Both needed)
Examiners report
Almost all candidates seemed familiar with reading cladograms and were able to answer this question.
Again almost all candidates were able to answer this question.
This was a more discriminating question. Many were able to score one mark for indicating that DNA from the tissue sample was amplified using PCR but few were able to give additional details needed to receive 2 or 3 marks. They tended to confuse the answer to this question with that of the following one.
This question on sequence alignment software was often confused with that on PCR. Better candidates were able to explain the use of BLAST software for DNA and protein sequences.
