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Date May 2018 Marks available 2 Reference code 18M.2.HL.TZ1.4
Level Higher level Paper Paper 2 Time zone Time zone 1
Command term List Question number 4 Adapted from N/A

Question

Sickle cell anemia is due to a single base substitution in DNA. Using the diagram, outline how this translates into the production of an abnormal hemoglobin molecule by completing the spaces labelled I, II and III.

[2]
a.

DNA codes for the amino acid sequence of polypeptides. List two other functions of DNA.

[2]
b.

Distinguish between the purpose of free and bound ribosomes.

 

[1]
c.

Markscheme

a. I: GUG
AND

II: CAC 

b. III: Val/valine

Both required. Do not accept GAG to GTC.

 

a.

a. promotion/repression/regulation of gene expression 

b. introns (have functions in regulation of gene expression) 

c. telomeres (form caps at the end of chromosomes) 

d. coding for tRNAs/rRNAs 

e. allows genes/traits/heritable characteristics to be passed to offspring

 

b.

free ribosomes produce proteins for use inside the cell/cytoplasm whereas bound ribosomes produce proteins for secretion/for use outside the cell/for use in lysosomes

c.

Examiners report

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

Syllabus sections

Core » Topic 2: Molecular biology » 2.7 DNA replication, transcription and translation
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