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Date November 2018 Marks available 1 Reference code 18N.3.SL.TZ0.10
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term Identify Question number 10 Adapted from N/A

Question

A section of mRNA contains the start codon for translation of a polypeptide by the ribosomes.

Identify the nucleotides of the start codon for the polypeptide.

[1]
a.

State the chemical difference between the 5' end and the 3' end of a DNA strand.

[1]
b.

Within the base sequence shown in the diagram, the sequence for the stop codon UGA appears. Explain the reasons for translation continuing beyond this point in the mRNA.

[2]
c.

Describe how bioinformatics can help identify genes within the DNA of an organism.

[2]
d.

Markscheme

AUG ✔

a.

5′ end contains a phosphate group «on carbon 5»
OR
3′ carbon contains a hydroxyl/OH group «on carbon 3» ✔

b.

a. the gene code occurs in triplets ✔

b. the stop codon would not be part of the reading frame ✔

c. the code for a polypeptide would contain more codons ✔

c.

a. bioinformatics is the application of computer technology to biological information
OR
information is stored in a database
OR
bioinformatics is used in analyzing genomes ✔

b. allows for searches/comparisons/analysis of ORF/open reading frame ✔

c. the computer searches for a start codon and a stop codon «and within a distance of 60+ codons» ✔

d.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.

Syllabus sections

Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.2 Biotechnology in agriculture
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Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics)
Option B: Biotechnology and bioinformatics

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