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Question 19N.2.SL.TZ0.2

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Date November 2019 Marks available [Maximum mark: 8] Reference code 19N.2.SL.TZ0.2
Level SL Paper 2 Time zone TZ0
Command term Annotate, Determine, Outline, State, Suggest Question number 2 Adapted from N/A
2.
[Maximum mark: 8]
19N.2.SL.TZ0.2

A short base sequence of mRNA and a table of the genetic code are shown below.

Sequence of mRNA

Table of the genetic code

(a)

Outline the function of codons.

[1]

Markscheme

«three bases on mRNA» coding for one amino acid «in a polypeptide» ✔

(b.i)

Determine the sequence of amino acids that could be translated from the sequence of mRNA.

[1]

Markscheme

met-ser-arg-arg
OR
start-ser-arg-arg
OR
met-ser-arg-arg-stop
OR
start-ser-arg-arg-stop ✔

Do not accept peptides containing an amino acid/leu for the last codon.

(b.ii)

Determine the DNA base sequence transcribed to form this sequence of mRNA.

[1]

Markscheme

TAC TCG GCT TCC ATC GAC ✔

(c)

Suggest a hypothesis that accounts for the slightly different meaning of some codons in a very limited number of organisms.

[1]

Markscheme

they occurred after the common origin of life OWTTE
OR
the genetic code is not «in fact» universal ✔

Look for alternatives.

The diagram shows a section of a polypeptide.

(d.i)

Annotate the diagram to show a peptide bond between two amino acids.

[1]

Markscheme

any annotation between a C=O and the next NH ✔

e.g.

(d.ii)

State the type of reaction that removes water while linking amino acids together to form polypeptides.

[1]

Markscheme

condensation ✔

Do not accept anabolism alone.

(e)

Outline the function of Rubisco and of spider silk in relation to their three-dimensional conformation.

[2]

Markscheme

Award [1] per correct row or correct column.

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