Mock Exam IB DP Biology SL Paper 2 Set 4

Question

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

$\text{AUGAGCCGAAGGUAGCUG}$

Table of the genetic code

   

a. Outline the function of codons.

b. (i) Determine the sequence of amino acids that could be translated from the sequence of mRNA.

b. (ii) Determine the DNA base sequence transcribed to form this sequence of mRNA.

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

d. The diagram shows a section of a polypeptide

     

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

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

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

 

Function

Conformation

Rubisco

  

Spider silk

  
Answer/Explanation

Ans:

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

 b i) 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.

ii) TAC TCG GCT TCC ATC GAC

c) they occurred after the common origin of life OWTTE

OR

the genetic code is not «in fact» universal  Look for alternatives.

d i) any annotation between a C=O and the next NH

ii) condensation

e)

 

Question

(a) Outline the cell theory.

(b) State two functions of life.

(c) List three characteristics of eukaryotic homologous chromosomes.

(d) Using the following table, compare and contrast anaerobic cell respiration in yeasts and in humans. The first row has been completed as an example.

Answer/Explanation

Ans:

a)

a. cells can only arise from preexisting cells 

b living organisms are composed of cells/smallest unit of life 

c organisms consisting of only one cell carry out all functions of life in that cell/cells perform life functions «at some point in their existence» 

d although most organisms conform to cell theory, there are exceptions 

b

a nutrition  Do not allow “feeding”, plants do not “feed”.

b metabolism/respiration 

c growth 

d response/irritability 

e excretion 

f homeostasis 

g reproduction

c

a linear DNA molecules OR DNA associated with histone «proteins» 

b carry the same sequence of genes 

c «but» not necessarily the same alleles «of those genes» 

d both are present when nucleus is in diploid state  OR occur in pairs 

e have same size/length/banding patterns 

f centromeres are in the same position

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