LIFE SCIENCES
GRADE 12
NATIONAL SENIOR CERTIFICATE
MEMORANDUM
JUNE 2017

SECTION A
QUESTION 1
1.1
1.1.1 A ✓✓
1.1.2 A ✓✓
1.1.3 B ✓✓
1.1.4 C ✓✓
1.1.5 C ✓✓
1.1.6 D ✓✓
1.1.7 B ✓✓
1.1.8 A ✓✓
1.1.9 B ✓✓
1.1.10 D ✓✓ (10 x 2) (20)
1.2
1.2.1 Axon \✓
1.2.2 Multiple sclerosis ✓
1.2.3 Parasympathetic ✓
1.2.4 Co-dominance ✓
1.2.5 Continuous variation ✓
1.2.6 Metaphase 2 ✓
1.2.7 Umbilical vein ✓
1.2.8 Non-disjunction ✓
1.2.9 Ribosome ✓
1.2.10 Anticodon ✓ (10 x 1) (10)
1.3
1.3.1 B only ✓✓
1.3.2 A only ✓✓
1.3.3 A only ✓✓ (3 x 2) (6)
1.4
1.4.1

1. Nucleus ✓ and Mitochondria  (2)
2. (DNA) replication ✓ (1)
3. Interphase ✓ (1)
4. Nucleotides ✓ (1)
5. 1 – Thymine ✓ 2 – Guanine ✓ 3 – (Weak) hydrogen bond ✓ (3)

1.5
1.5.1

1. 8/16 = ½ = 50% ✓
2. 4/16 = ¼ = 25% ✓(1)

1.5.2

1. Ry ✓ (1)
2. Ry, ry ✓ (1)

1.5.3 (e) Round and green ✓ (1)
1.5.4 8 Round yellow : 8 Round green = 1 : 1 ✓ (1)
TOTAL SECTION A: 50

SECTION B
QUESTION 2
2.1
2.1.1
A – Nuclear membrane ✓ (1)
C – Nucleoplasm ✓ (1)
D – Cytoplasm ✓ (1)
2.1.2

1. Prophase 1 ✓ (1)
2. Metaphase 1 ✓ (1)

2.1.3 Homologous chromosomes ✓/ Bivalent (1)
2.1.4 Crossing over ✓(1)
2.1.5

(3)
2.2
2.2.1

1. 21 ✓ (1)
2. 6 ✓ (1)
3. 7 ✓ (1)

2.2.2 8 – GUG ✓ (1)
9 – CUG ✓ (1)
10 – ACU ✓ (1)
11 – CCU ✓ (1)
2.2.3

1. Valine ✓ (1)
2. Histidine ✓ (1)
3. Leucine ✓ (1)

2.2.4

1. Gene mutation ✓ (1)
2. Glutamate ✓ (1)

2.2.5

• Since the sequence of nitrogenous bases in a gene ✓
• determines the sequence of amino acids ✓ in a protein molecule
• a mutation can change the amino acid sequence of the resulting protein. ✓
• Formation of a different protein ✓ leads to
• abnormal metabolism or cessation of metabolic activity ✓/ not functional. (Any 3 x 1) (3)
  (15)

2.3
2.3.1 An increase / decrease in light intensity will cause, the diameter of the pupil to decrease / increase. ✓✓
OR
The diameter of the pupil will increase / decrease as the light intensity increases / decreases.
OR
An increase in light intensity will have no effect on the diameter of the pupil. ✓✓ (2)
2.3.2

1. The diameter of pupil ✓ (1)
2.  
   • The distance between the source of light and the position of the eye. ✓
   • Same eye used at various light intensities. ✓
   • Surrounding light must be kept at 0 lux ✓/dark. (Any 1 x 1) (1)

2.3.3 The diameter of pupil measured at 0 lux was used as a control ✓ to compare ✓ any change in diameter at various light intensities. (2)
2.3.4 7 – 2 = 5
5 ×100 ✓ =71,4% ✓ (2)
7 
2.3.5 Under high light intensity:

• The circular muscles of the iris contract ✓
• The radial muscle relax ✓
• The pupil constricts ✓
• The amount of light entering the eye is reduced. ✓ (4)

2.3.6 When the retina is exposed to high intensity light, the photoreceptor cells ✓ (rods and cones) will be damaged or destroyed ✓ causing blindness. ✓ (3)
[40]

QUESTION 3
3.1
3.1.1

Related Items

1. Normal female  (1)
2. X^DX^d ✓ (1)

3.1.2

• Colour blindness is caused by a recessive allele ✓
• Carried on the X chromosomes ✓
• Females have two X chromosomes ✓ / Male only have one X chromosome
• Females must inherit two copies of the recessive allele ✓/ females who inherit only one of the recessive allele are still normal.
  (Any 3 x 1) (3)

3.1.3

*50% chance of having a colour blind son
P₃ and F₃ (P₁ and F₁) ✓
Meiosis and fertilisation✓
(*1 Compulsory + Any 6) (7)
OR

P₃ and F₃ (P₁ and F₁) ✓
Meiosis and fertilisation✓
(*1 compulsory + Any 6) (7)
3.2
3.2.1 The shedding of the endometrium lining ✓ of the uterus accompanied by bleeding, ✓ occurs once in about 28 days. (2)
3.2.2 On the 14th ✓ day of the menstrual cycle. (1)
3.2.3

1. The endometrium lining becomes thinner ✓/ decreases as it breaks down and detach from the uterus. (1)
2. The endometrium wall gradually becomes thicker, ✓ more vascular and glandular. (1)

3.2.4

• The pituitary gland begins to secrete hormone oestrogen ✓ from the day 7 causing endometrium wall to become thicker, more vascular glandular. ✓
• The Luteinizing hormone ✓ secreted by the pituitary gland, causes ovulation ✓ / and converts the empty Graafian follicle into a structure called corpus luteum.
• The corpus luteum secretes a hormone known progesterone  which causes further thickening of endometrium ✓ lining to prepare it for possible implantation of an embryo. (6)

3.2.5

• The higher levels of progesterone ✓ inhibit the secretion of FSH ✓ by the pituitary gland
• so that no further development of Graafian follicles ✓ to release mature ovum (ovulation) ✓ that may lead to possible fertilisation. (4)

3.3
3.3.1 An organism’s complete set of genes. (1)
3.3.2 The cloning involves the transfer of a nucleus from the cell of an animal with a desirable trait  into the ovum of another animal where the nucleus have been removed.✓ (2)
3.3.3

• To assess the risks to human health ✓ / environment
• To determine if the presence of the transferred gene will affect the expression of other genes ✓
• To test the effectiveness of the product ✓ (Any 1 x 1) (1)

3.3.4

• Produce crops that are resistant to adverse conditions ✓/ drought/ disease / pests.
• Increase crop yield. ✓
• Change the time for the ripening of fruits. ✓
• Increase shelf life of plant products. ✓
• Improve nutritional value of food. ✓
• Improve the taste of food. ✓
• Developing fruit/ plants with desirable characteristics. ✓ (Any 3 x 1) (3)

3.4

• The mitochondria contain (mitochondrial) DNA ✓
• At fertilisation, only the nucleus of the sperm cell enters the egg ✓
• to fuse with the nucleus of the egg cell. ✓
• Therefore, the zygote still contains the mitochondria and hence the mitochondrial DNA of the egg cell from the mother ✓
• This DNA is passed from mother to child. ✓
• Mutations in mitochondrial DNA enable us to trace our female line of descent. ✓ (6)

[40]

SECTION C
QUESTION 4
*Accommodation of the eye ✓

• The ciliary muscle relax ✓
• Suspensory ligaments become taut ✓
• Tension on the lens increases ✓
• The lens becomes flattened (less convex) ✓
• The refractive power of the lens is decreased ✓
• A clear image of the distant object which is the traffic robot is now focused on the retina ✓ (*1 compulsory mark + Any 4) (5)

Hearing

• Pinna traps / directs the sound waves ✓
• Into the ear canal ✓/ meatus
• This causes the tympanic membrane to vibrate
• The vibration is transmitted to the auditory ossicles ✓/ name all 3
• The ossicles amplify the vibration ✓
• And transmit it to the oval window ✓
• The oval window vibrates ✓
• Creating waves ✓
• In the fluid / endolymph of the cochlea ✓
• Which stimulates the Organ of corti ✓
• To convert the wave into an impulse ✓
• The impulse travels along the auditory nerve ✓
• to the cerebrum ✓
• where it is interpreted as the siren of an ambulance. (Max. 7) (7)

Restoring balance

• The maculae ✓
• In the utriculus and sacculus ✓ and
• The cristae ✓
• In the semi-circular canals ✓ are stimulated
• They generate impulses ✓
• Which is transmitted through the auditory nerve ✓
• To the cerebellum ✓ where they are interpreted
• Impulses are transmitted via the motor neuron ✓
• to skeletal muscles ✓ (Max. 5)

Content:(17)
Synthesis:(3)
(20)

ASSESSING THE PRESENTATION OF THE ESSAY

TOTAL SECTION C: 20
GRAND TOTAL: 150