| Date | November 2017 | Marks available | 1 | Reference code | 17N.3.HL.TZ0.10 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Identify | Question number | 10 | Adapted from | N/A |
Question
The table shows a comparison of DNA base sequences in several yeast (Saccharomyces) genomes.
[Source: P. F. Cliften et al. (2001) ‘Surveying Saccharomyces Genomes to Identify Functional Elements by Comparative DNA Sequence Analysis’, Genome Research, 11, pp. 1175–1186. © Cold Spring Harbor Laboratory Press. Reproduced with permission.]
Identify the species that has the lowest percentage of coding sequences.
State how similar nucleotide sequences can be identified.
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.
Outline possible medical applications of the polymerase chain reaction (PCR).
Markscheme
S. unisporus
BLASTn/sequence alignment software
“n” required in BLASTn
a. easy to grow
OR
easy/cheap to produce large amounts
OR
fast generation time
b. genomes are small/easy to manipulate
c. metabolically diverse
d. industrial applications/biopharming
e. no ethical issues «with yeast»
[Max 3 Marks]
a. identify different viral/influenza strains
b. genetic testing/testing for genetic disease mutations
c. tissue typing
d. vaccine development
[Max 1 Mark]
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.TZ0.10b: 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.
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17M.3.HL.TZ1.12:
Explain how BLAST searches are carried out and the applications of different types of these searches.
- 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.
