NATIONAL SENIOR CERTIFICATE EXAMINATION
NOVEMBER 2020
LIFE SCIENCES: PAPER I
Time: 3 hours 200 marks
PLEASE READ THE FOLLOWING INSTRUCTIONS CAREFULLY
1. This question paper consists of 15 pages and a yellow Answer Booklet of 16 pages
(i–xvi). Please check that your question paper is complete. Detach the yellow
Answer Booklet from the middle of the question paper. Remember to write your
examination number in the blocks provided.
2. This question paper consists of four questions.
3. Question 1 must be answered in the yellow Answer Booklet provided.
4. Questions 2, 3 and 4 must be answered in your Answer Book.
5. Start each question on a new page.
6. Read the questions carefully.
7. Number the answers exactly as the questions are numbered.
8. Use the total marks that can be awarded for each of Questions 1, 2, 3 and 4 as an
indication of the detail required.
9. It is in your own interest to write legibly and to present your work neatly.
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,NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER I Page 2 of 15
QUESTION 2
2.1 Haemoglobin molecules are made during the process of protein synthesis.
The genetic code for making haemoglobin is stored in the DNA of cells.
2.1.1 State TWO differences in structure between DNA and RNA. (2)
2.1.2 Name the process in a cell which results in the formation of mRNA. (1)
2.1.3 Name the location in the cell where mRNA would be made. (1)
2.1.4 (a) The following sequence of nitrogen bases is part of the DNA
template that makes part of the haemoglobin molecule.
ACA CCT GAG
Use the above template strand of DNA to write the
corresponding mRNA nucleotide sequence. (3)
(b) Use the mRNA codon table below to write down the amino
acids coded for by the mRNA in the correct order.
mRNA codon table
Key
green
1st
base of
codon
orange
2nd
base of
codon
yellow
3rd
base of
codon
Purple
amino
acids
a
[Adapted: <https://slideplayer.com>]
(3)
2.1.5 Draw a flow diagram to represent the steps in the synthesis of a
protein (such as the haemoglobin molecule) in the cytoplasm of the
cell. (6)
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,NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER I Page 3 of 15
2.1.6 Haemoglobin is a single chain of 147 amino acids. Calculate the
number of nucleotides that would code for this protein molecule.
Show all working. (2)
2.2 Haemoglobin molecules are protein molecules found in the red blood cells
of humans. Haemoglobin molecules serve as the oxygen carriers in the
blood. A mutation in the gene coding for haemoglobin can cause a serious
condition known as sickle-cell anaemia, where the red blood cells have an
abnormal sickle cell shape. Individuals with this disease suffer from
anaemia, periodic episodes of pain, swollen hands and feet and frequent
infections.
Diagram showing normal red blood cells and sickle cells
Cross-section of Normal Red blood
normal red blood cell haemoglobin cells are soft
A and flexible
and break
down after
120 days
Normal red blood cells flow
freely in the blood vessel
Cross-section of Abnormal haemoglobin
sickle cell forms strands that cause Red blood
the sickle cells are hard
B
shape
and break
down after
16 days
Sticky sickle cells block blood flow
[Adapted: <Biological Sciences Review>]
2.2.1 Use the information given in the diagram to tabulate THREE
differences between a normal red blood cell and a sickle cell. (5)
2.2.2 The mutant allele for sickle-cell anaemia is recessive. Draw a genetic
cross/Punnett square to determine the probability of parents who are
both heterozygous for sickle-cell having a child with sickle-cell
anaemia. Show the ratios of all the phenotypes arising from the
cross.
Use the following key:
N – normal n – sickle-cell (6)
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2.3 One possible strategy to cure sickle-cell disease uses CRISPR/Cas9
technology to edit a mutant gene in the stem cells that give rise to other
blood cells of patients. The healthy cells are then placed back into the
patient's red bone marrow. The image below depicts this process.
Stem cell with Stem cell with
mutation corrected genotype
CRISPR/Cas9 editing
Placed in bone
marrow
Sickle-cell disease Sickle-cell red blood Healthy red
patient cells blood cells
[Adapted: <https://cen.acs.org>]
2.3.1 State whether the following statements regarding the information
shown in the above diagram are TRUE or FALSE.
(a) CRISPR/Cas9 can be used to edit parts of the human
genome. (1)
(b) The mutation in the stem cell is a substitution point mutation. (1)
(c) CRISPR/Cas9 technology will correct the mutation in every
cell of the patient. (1)
(d) The process shown in the diagram is a form of gene therapy. (1)
2.3.2 Clinical trials using this process to treat sickle-cell anaemia are
underway. Suggest TWO important reasons why clinical trials should
be carried out before making this technique available to all sickle-cell
anaemia patients. (2)
IEB Copyright © 2020
NOVEMBER 2020
LIFE SCIENCES: PAPER I
Time: 3 hours 200 marks
PLEASE READ THE FOLLOWING INSTRUCTIONS CAREFULLY
1. This question paper consists of 15 pages and a yellow Answer Booklet of 16 pages
(i–xvi). Please check that your question paper is complete. Detach the yellow
Answer Booklet from the middle of the question paper. Remember to write your
examination number in the blocks provided.
2. This question paper consists of four questions.
3. Question 1 must be answered in the yellow Answer Booklet provided.
4. Questions 2, 3 and 4 must be answered in your Answer Book.
5. Start each question on a new page.
6. Read the questions carefully.
7. Number the answers exactly as the questions are numbered.
8. Use the total marks that can be awarded for each of Questions 1, 2, 3 and 4 as an
indication of the detail required.
9. It is in your own interest to write legibly and to present your work neatly.
IEB Copyright © 2020 PLEASE TURN OVER
,NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER I Page 2 of 15
QUESTION 2
2.1 Haemoglobin molecules are made during the process of protein synthesis.
The genetic code for making haemoglobin is stored in the DNA of cells.
2.1.1 State TWO differences in structure between DNA and RNA. (2)
2.1.2 Name the process in a cell which results in the formation of mRNA. (1)
2.1.3 Name the location in the cell where mRNA would be made. (1)
2.1.4 (a) The following sequence of nitrogen bases is part of the DNA
template that makes part of the haemoglobin molecule.
ACA CCT GAG
Use the above template strand of DNA to write the
corresponding mRNA nucleotide sequence. (3)
(b) Use the mRNA codon table below to write down the amino
acids coded for by the mRNA in the correct order.
mRNA codon table
Key
green
1st
base of
codon
orange
2nd
base of
codon
yellow
3rd
base of
codon
Purple
amino
acids
a
[Adapted: <https://slideplayer.com>]
(3)
2.1.5 Draw a flow diagram to represent the steps in the synthesis of a
protein (such as the haemoglobin molecule) in the cytoplasm of the
cell. (6)
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,NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER I Page 3 of 15
2.1.6 Haemoglobin is a single chain of 147 amino acids. Calculate the
number of nucleotides that would code for this protein molecule.
Show all working. (2)
2.2 Haemoglobin molecules are protein molecules found in the red blood cells
of humans. Haemoglobin molecules serve as the oxygen carriers in the
blood. A mutation in the gene coding for haemoglobin can cause a serious
condition known as sickle-cell anaemia, where the red blood cells have an
abnormal sickle cell shape. Individuals with this disease suffer from
anaemia, periodic episodes of pain, swollen hands and feet and frequent
infections.
Diagram showing normal red blood cells and sickle cells
Cross-section of Normal Red blood
normal red blood cell haemoglobin cells are soft
A and flexible
and break
down after
120 days
Normal red blood cells flow
freely in the blood vessel
Cross-section of Abnormal haemoglobin
sickle cell forms strands that cause Red blood
the sickle cells are hard
B
shape
and break
down after
16 days
Sticky sickle cells block blood flow
[Adapted: <Biological Sciences Review>]
2.2.1 Use the information given in the diagram to tabulate THREE
differences between a normal red blood cell and a sickle cell. (5)
2.2.2 The mutant allele for sickle-cell anaemia is recessive. Draw a genetic
cross/Punnett square to determine the probability of parents who are
both heterozygous for sickle-cell having a child with sickle-cell
anaemia. Show the ratios of all the phenotypes arising from the
cross.
Use the following key:
N – normal n – sickle-cell (6)
IEB Copyright © 2020 PLEASE TURN OVER
, NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER I Page 4 of 15
2.3 One possible strategy to cure sickle-cell disease uses CRISPR/Cas9
technology to edit a mutant gene in the stem cells that give rise to other
blood cells of patients. The healthy cells are then placed back into the
patient's red bone marrow. The image below depicts this process.
Stem cell with Stem cell with
mutation corrected genotype
CRISPR/Cas9 editing
Placed in bone
marrow
Sickle-cell disease Sickle-cell red blood Healthy red
patient cells blood cells
[Adapted: <https://cen.acs.org>]
2.3.1 State whether the following statements regarding the information
shown in the above diagram are TRUE or FALSE.
(a) CRISPR/Cas9 can be used to edit parts of the human
genome. (1)
(b) The mutation in the stem cell is a substitution point mutation. (1)
(c) CRISPR/Cas9 technology will correct the mutation in every
cell of the patient. (1)
(d) The process shown in the diagram is a form of gene therapy. (1)
2.3.2 Clinical trials using this process to treat sickle-cell anaemia are
underway. Suggest TWO important reasons why clinical trials should
be carried out before making this technique available to all sickle-cell
anaemia patients. (2)
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