| Date | May 2017 | Marks available | 6 | Reference code | 17M.3.HL.TZ1.12 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
Explain how BLAST searches are carried out and the applications of different types of these searches.
Markscheme
Process (max [5]):
a. BLAST «Basic Local Alignment Search Tool» search enables comparison of an unknown sequence with databases of sequences
b. «software» finds similar sequences / aligns sequences by locating matches between two sequences
c. carries out statistical calculations «to find matches with other sequences»
d. BLASTn used to align/show similarities in nucleotide sequences in nucleic acids
e. BLASTp used to align/show similarities in amino acid sequences in proteins
f. used to identify the gene of a protein
Application (max [2]):
g. one application of BLAST
h. second application of BLAST
eg BLAST can be used for identifying species / locating domains / establishing phylogeny / DNA mapping / other verifiable examples
Examiners report
Syllabus sections
- 17M.3.SL.TZ1.16a: Calculate the diversity of site C. Working should be shown.
- 18M.3.HL.TZ2.12b: Regulations say that a protein is considered allergenic and unsafe for human consumption if...
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18M.3.HL.TZ1.12a:
Caenorhabditis elegans, a nematode, was the first multicellular organism whose genome was completely sequenced.
Outline the benefits of using model organisms for studying gene function.
- 18N.3.HL.TZ0.11d: A bioinformatics analysis was performed on the protein PSY transcribed from the gene from...
- 16N.3.HL.TZ0.12e: Determine which two genera are most closely related according to their cytochrome c protein...
- 17N.3.HL.TZ0.10a: Identify the species that has the lowest percentage of coding sequences.
- 17N.3.HL.TZ0.10b: State how similar nucleotide sequences can be identified.
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16N.3.HL.TZ0.12c:
(i) Identify the longest amino acid sequence where there are no differences amongst the five genera.
(ii) Suggest, with a reason, whether the DNA coding for the amino acid sequence identified in (c)(i) must be identical for the five genera.
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16N.3.HL.TZ0.12b:
State the meaning of the dash (–) in the alignment.
- 18N.3.SL.TZ0.10d: Describe how bioinformatics can help identify genes within the DNA of an organism.
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18M.3.HL.TZ1.12b:
Describe how BLAST can be used to establish phylogenetic relationships between several organisms.
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18N.3.HL.TZ0.11f:
In the alignment there are dashes (–) in some positions. Deduce what is indicated by these dashes.
- 18N.3.HL.TZ0.11e: BLASTp was used to obtain the alignment of the genes coding for PSY. Outline reasons for...
- 18M.3.HL.TZ2.12a.ii: Outline how the similar protein sequences were found.
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
- 16N.3.HL.TZ0.12a: State the bioinformatics tool used to obtain the alignment.
- 16N.3.HL.TZ0.12d: Describe briefly how the cladogram was obtained.
- 17M.3.HL.TZ1.9b: Explain what the branching off points represent in the cladogram of these fungi.
- 18M.3.HL.TZ2.12a.i: State a bioinformatic search tool that could be used to perform the alignment.
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17N.3.HL.TZ0.10c:
The yeast Saccharomyces cerevisiae was the first eukaryotic organism to have its entire genome sequenced. Suggest reasons for the choice of yeast as a study organism.
