HL Paper 1
Some regions of DNA do not code for the production of proteins. What are these regions of DNA used as?
A. They have no known function and are recycled to provide nucleotides
B. Gene regulation and coding for production of enzymes used in translation
C. Telomeres and coding for production of tRNA
D. Introns and coding for production of structural proteins
The diagram shows the three-dimensional structure of tRNA.
[Source: Structure reproduced with the kind permission of N.R. Voss.]
What can attach to the region marked X?
A. mRNA
B. An amino acid
C. An anticodon
D. The P site of the ribosome
The diagram shows the arrangement of introns and exons in a segment of pre-mRNA. Pre-mRNA is immature mRNA containing introns and exons.
Which is a mature mRNA molecule derived from the pre-mRNA by splicing?
[Source: © International Baccalaureate Organization 2019]
The graph shows results of an experiment by Hershey and Chase in 1952 in which bacteria were infected with a mixture of virus particles labelled with either 32P or 35S. A suspension of the infected bacteria was agitated with a blender, and samples collected from the suspension were centrifuged to record the percentage of isotope remaining on the outside of the cells.
[Source: Republished with permission of ROCKEFELLER UNIVERSITY PRESS, from Independent functions of protein and nucleic acid in growth of bacteriophage. Hershey, A.D. and Chase, M., 1952. (Journal of General Physiology, 36(1), p.47). Society of General Physiologists, Rockefeller Institute for Medical Research, Rockefeller Institute; permission conveyed through Copyright Clearance Center, Inc.]
What do curves X and Y represent?
Scientists have heated a solution containing the protein albumin and measured its relative alpha helix content, shown on the graph.
What does the zone labelled X indicate?
A. Rapid increase in beta pleated sheets
B. Rapid formation of hydrogen bonds
C. Rapid increase in denatured protein molecules
D. Rapid decrease in peptide bonds
The diagram shows the structure of a nucleosome.
[Source: Zephyris. Nucleosome 1KX5 colour coded. Available at https://en.wikipedia.org/wiki/Nucleosome#/media/File:Nucleosome_1KX5_colour_coded.png
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license (https://creativecommons.org/licenses/by-sa/3.0/deed.en).]
What is the structure labelled T?
A. 5' end of RNA
B. 5' end of uncoiled DNA
C. N-terminal tail of one DNA strand
D. N-terminal tail of one histone
Rosalind Franklin produced X-ray diffraction images of DNA.
[Source: © King’s College, London. KCL Department of Biophysics KDBP/1/1.]
Which previously unknown aspect of DNA was deduced from these images?
A. Chromosomes are made of DNA.
B. Deoxyribose sugar is attached to a phosphate group.
C. The base A pairs with T and C with G.
D. The DNA molecule is a double helix.
What is the primary function of the free ribosomes shown in the electron micrograph?
[Source: J Gordon Betts, et al. Anatomy and Physiology. Houston Texas: OpenStax, 2013. https://openstax.org/books/
anatomy-and-physiology/pages/3-2-the-cytoplasm-and-cellular-organelles. Image file available at https://commons.
wikimedia.org/wiki/File:0313_Endoplasmic_Reticulum.jpg#/media/File:0313_Endoplasmic_Reticulum_b_labeled.
png. This file is licensed under the Creative Commons Attribution 3.0 Unported license. https://creativecommons.org/
licenses/by/3.0/deed.en.]
A. Synthesize proteins to be used within the cell
B. Synthesize proteins for use in lysosomes
C. Carry amino acids to mRNA for protein synthesis
D. Synthesize proteins for secretion
This DNA sequence was used to synthesize a polypeptide.
DNA (sense strand): 3′ T A C T G A 5′
DNA (template strand): 5′ A T G A C T 3′
Which are the bases of the tRNA (anticodons)?
A. T A C T G A
B. U A C U G A
C. A U G A C U
D. A T G A C T
The mRNA codon UAC codes for the amino acid tyrosine. Which tRNA carries tyrosine?
How can environmental factors affect the expression of genes?
A. By promoting the replication of nucleosomes
B. By inactivating epinephrine
C. By making specific changes to the base sequence of genes
D. By causing the pattern of DNA methylation to be changed
Current understanding of DNA is an example of the accumulated discoveries of many scientists. Which scientists are credited with establishing that DNA is the genetic material?
A. Franklin and Wilkins
B. Watson and Crick
C. Meselson and Stahl
D. Hershey and Chase
The number of protein-coding genes in the human genome is estimated to be about 20 000, which is much less than the size of the proteome. What is one reason for this?
A. Exons are removed from RNA before translation.
B. There are more types of amino acids than nucleotides.
C. mRNA can be spliced after transcription.
D. Base substitutions occur during transcription.
In which image are polysomes visible? (The images do not have the same magnification)
During modification in eukaryotes, mRNA is spliced. What is splicing of mRNA?
A. Separation of mRNA from DNA during transcription
B. The removal of non-coding RNA sections in prokaryotic cells
C. Linking together exons
D. Replacement of primers with RNA bases
The diagram shows how pre-mRNA is processed into mature mRNA. Which structures are indicated by the letters W and X?
Gene expression in cells is regulated at various stages. During which stage does splicing of RNA occur?
A. During replication
B. During transcription
C. Post transcription
D. Translation
What is the difference between the DNA of adult identical (monozygotic) twins?
A. Order of genes
B. Sequence of nucleotides
C. Methylation pattern
D. Ratio of complementary base pairs
What are polysomes?
A. Strings of amino acids
B. Packages of eight histones with DNA
C. Many ribosomes joined to one mRNA
D. Complexes of tRNA with amino acids
How do R group interactions contribute to protein structure?
I. Determining the sequence of amino acids in the primary structure
II. Stabilizing beta pleated sheets in the secondary structure
III. Stabilizing further foldings of a polypeptide into a tertiary structure
A. I only
B. II and III only
C. III only
D. I, II and III
In the diagram of a ribosome, which letter indicates the P site?
[Source: iStock.com/ttsz]
What does eukaryotic DNA have that is missing from prokaryotic DNA?
A. Uracil
B. Promoter DNA
C. Introns
D. Coding sequences
What applies to DNA base sequences?
I. Some genes do not code for proteins.
II. Promoters are transcribed along with the gene.
III. Introns are only found within genes coding for proteins.
A. I only
B. II only
C. II and III only
D. I, II and III
Which regions of DNA code for the production of specific proteins?
A. Telomeres
B. Genes for ribosomal RNA
C. Exons
D. Regulators of gene expression
The image shows a replication fork.
Which row identifies X, Y and Z in the diagram?
Which statement applies to tRNA?
A. There is at least one type of tRNA that combines with each known amino acid.
B. One type of tRNA can combine with all of the known amino acids.
C. tRNA carries out its main role within the nucleus.
D. tRNA is produced by the process of translation.
Which cell component synthesizes actin and myosin?
A. Free ribosomes
B. Rough endoplasmic reticulum
C. Smooth endoplasmic reticulum
D. Nuclear membrane
What is a feature of transcription in the single-celled organism shown in the electron micrograph?
[Source: George E. Palade Electron Microscopy Slide Collection Harvey Cushing/John Hay Whitney Medical Library Yale University Library.]
A. mRNA splicing
B. Removal of introns
C. Codon-anticodon binding
D. Synthesis of RNA in a 5′ to 3′ direction
The diagram shows the structure of E. coli ribonuclease HI, a bacterial protein consisting of one polypeptide chain.
[Source: RCSB PDB. 1JL1 D10A E. coli ribonuclease HI. PDB DOI: 10.2210/pdb1JL1/pdb Mol* (Goedken, E.R., Marqusee, S. Native-state energetics of a thermostabilized variant of ribonuclease HI. (2001) J Mol Biol 314:
863–871 DOI:10.1006/jmbi.2001.5184) [image online] Available at: https://www.rcsb.org/structure/1jl1
[Accessed 25 November 2019]. This file is licensed under the Creative Commons CC0 1.0 Universal (https://creativecommons.org/publicdomain/zero/1.0/).]
Which level(s) of protein structure is/are shown?
A. Alpha helix only
B. Quaternary only
C. Primary and secondary
D. Secondary and tertiary
The image shows a polysome in a bacterial cell.
[Source: © International Baccalaureate Organization 2019]
How many genes have been transcribed?
A. 1
B. 2
C. 3
D. 4
Which letter (A–D) indicates where a new nucleotide would attach?
Which are two proteins that assist in the unwinding and separation of DNA strands during replication?
A. Helicase and DNA polymerase III
B. DNA gyrase and DNA polymerase I
C. Helicase and DNA primase
D. Single-strand binding protein and DNA gyrase
A nucleotide containing dideoxyribose is shown.
What is the reason for the use of dideoxyribonucleotides to terminate sequences in base sequencing?
A. Nucleotides cannot form 5′ to 3′ linkages with dideoxyribonucleotides.
B. Nucleotides cannot form base pairs with dideoxyribonucleotides.
C. Dideoxyribonucleotides cannot form hydrogen bonds with deoxyribose.
D. Dideoxyribonucleotides do not have all four nitrogenous bases.
Where does a tRNA-activating enzyme attach the appropriate amino acid to the tRNA molecule?
What are the functions of DNA primase and DNA polymerase I in DNA replication?
Hershey and Chase used a bacteriophage (a virus that infects bacteria) to investigate the chemical nature of genes. The diagram shows a bacteriophage.
[Source: Graham Knott and Christel Genoud, ‘Commentary: is EM dead?’, Journal of Cell Science (2013),
126: 4545–4552, reproduced with permission. http://jcs.biologists.org/content/126/20/4545.figures-only
doi: 10.1242/jcs.124123 http://www.biologists.com/journal-of-cell-science]
The sulphur in the protein and the phosphorus in the DNA of the bacteriophage were radioactively labelled. The data obtained after bacterial infection and centrifugation are shown in the table.
What did Hershey and Chase conclude from their experiment?
A. DNA was mainly outside the bacterial cells.
B. Viruses infect bacterial cells with proteins.
C. Viral DNA was found within the bacterial cells.
D. Neither protein nor DNA were chemicals making up genes in viruses.
In which process(es) do nucleosomes play a role in eukaryotes?
I. tRNA activation
II. Transcription regulation
III. DNA supercoiling
A. I only
B. II only
C. II and III only
D. I, II and III
This image is taken from a visualization of a eukaryotic ribosome. The arrows show the direction of movement of mRNA. Which letter represents a tRNA exiting from the E site?
What is a function of DNA polymerase I?
A. Adds nucleotides in a 5’ to 3’ direction to elongate the chain
B. Uncoils the DNA double helix and splits it into two template strands
C. Removes RNA primer and replaces it with DNA
D. Produces sugar-phosphate bonds to link Okazaki fragments
What does post-transcriptional modification of eukaryotic mRNA include?
I. Introns are removed from mRNA.
II. Exons are joined together to form mature mRNA.
III. A 5' cap and 3' poly-A tail are added to mRNA.
A. I only
B. I and III only
C. II and III only
D. I, II and III
Promoters are non-coding regions in DNA. What is the role of a promoter?
A. It starts translation.
B. It starts mRNA splicing.
C. It is a binding site for DNA polymerase during DNA replication.
D. It is a binding site for RNA polymerase during transcription.
What contribution did the X-ray diffraction conducted by Rosalind Franklin make to our understanding of DNA?
A. It identified DNA as the genetic material.
B. It indicated the helical shape of the molecule.
C. It showed that the DNA of eukaryotes was associated with histone proteins.
D. It showed that replication was a semi-conservative process.
Variations in the types of antibodies are produced by mRNA splicing. What is an advantage of this process?
A. Reduces the size of mRNA required for the translation of antibodies
B. Increases the number of different antibodies that can be synthesized
C. Ensures that one gene codes for one antibody
D. Speeds up transcription of antibodies
Which types of interactions are found in a part of a protein with secondary but not tertiary structure?
I. Hydrogen bonds
II. Disulphide bridges
III. Ionic bonds
A. I only
B. I and II only
C. II and III only
D. I, II and III