| Date | November 2019 | Marks available | 1 | Reference code | 19N.3.hl.TZ0.13 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | List | Question number | 13 | Adapted from | N/A |
Question
DNA, deoxyribonucleic acid, is made up of nucleotides.
List two components of nucleotides.
Explain how the double-helical structure of DNA is stabilized once formed.
Markscheme
Any two correct for [1]:
pentose «sugar»
OR
deoxyribose ✔
phosphate/phosphato «group»/residue of phosphoric acid ✔
NOTE: Accept “−OPO32−/−OPO3H−/−OPO3H2” but not “PO43−”.
«organic» nitrogenous base
OR
nucleobase
OR
nucleic base
OR
purine
OR
pyrimidine ✔
NOTE: Accept the four bases together: “adenine/A, guanine/G, cytosine/C, thymine/T”.
Accept names or formulas.
Any two of:
H-bonding between bases in each pair ✔
hydrophobic interactions/π-stacking between bases ✔
polar/charged/hydrophilic groups in sugar-phosphate backbone interactions with aqueous solution/water
OR
H-bonding AND ion-dipole interactions between phosphato «groups» andwater/histones ✔
Accept "phosphate groups are hydrophilic and form H-bonds with water".
Accept “H-bonding with histones”.
Examiners report
Syllabus sections
-
17N.3.hl.TZ0.13:
The stability of DNA is due to interactions of its hydrophilic and hydrophobic components.
Outline the interactions of the phosphate groups in DNA with water and with surrounding proteins (histones).
-
17M.3.hl.TZ2.15a:
Outline how its structure allows it to be negatively charged in the body.
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17M.3.hl.TZ1.15d:
The sequence of nitrogenous bases in DNA determines hereditary characteristics.
Calculate the mole percentages of cytosine, guanine and thymine in a double helical DNA structure if it contains 17% adenine by mole.
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18M.3.hl.TZ1.6d:
Describe how DNA determines the primary structure of a protein such as insulin.
- 18N.3.hl.TZ0.7b: Suggest one concern about the use of genetically modified, GM, food.
- 18N.3.hl.TZ0.7a: State the feature of DNA that determines the primary structure of proteins synthesised by a...
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16N.3.hl.TZ0.15b:
In 2010, scientists claimed that they had discovered a species of bacteria capable of incorporating arsenic in place of phosphorus into the bacterial DNA. This claim has since proved controversial. Suggest one technique or evidence that might help support the claim.
- 16N.3.hl.TZ0.15a: State the name of the component of DNA responsible for the migration of its fragments to the...
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17M.3.hl.TZ2.15b:
Deduce the nucleotide sequence of a complementary strand of a fragment of DNA with the nucleotide sequence –GACGGATCA–.
- 19N.3.hl.TZ0.13b: Explain how the double-helical structure of DNA is stabilized once formed.
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18M.3.hl.TZ2.12:
DNA is a biopolymer made up of nucleotides. List two components of a nucleotide.
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19M.3.hl.TZ1.14a:
Outline what is meant by genetically modified organisms.
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19M.3.hl.TZ2.10b:
Describe what is meant by the genetic code and how it relates to protein synthesis.
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20N.3.hl.TZ0.8b(ii):
The diverse functions of biological molecules depend on their structure and shape.
Draw the nitrogenous base that is paired with guanine in DNA, showing the hydrogen bonds between the bases. Use section 34 of the data booklet.
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19M.3.hl.TZ1.14b:
Outline one benefit of the use of these products.
