LIFE SCIENCES
GRADE 12
MEMORANDUM
NATIONAL SENIOR CERTIFICATE
JUNE 2018

SECTION A
QUESTION 1
1.1
1.1.1 B ✓✓
1.1.2 C ✓✓
1.1.3 B ✓✓
1.1.4 C ✓✓
1.1.5 D ✓✓
1.1.6 A ✓✓
1.1.7 A ✓✓
1.1.8 C ✓✓
1.1.9 B ✓✓
1.1.10 C ✓✓ (10 x 2)
(20)
1.2
1.2.1 Eustachian tube ✓
1.2.2 Retina ✓
1.2.3 Ganglion ✓/Ganglia
1.2.4 Homozygous ✓/Homozygote
1.2.5 Chiasma ✓/ Chiasmata
1.2.6 Metaphase 1 ✓
1.2.7 Chromatids ✓
1.2.8 Semen ✓
1.2.9 DNA profiling ✓
1.2.10 Centromere ✓ (10 x 1)
(10)
1.3
1.3.1 A only ✓✓
1.3.2 B only✓✓
1.3.3 None ✓✓ (3 x 2) (6)
1.4
1.4.1

1. Receptors ✓ (1)
2. Grey matter ✓ (1)

1.4.2 C ✓ – Central canal ✓ (2)
1.4.3 E ✓/ motor neuron (1)
1.5
1.5.1

1. Gamete A/B ✓ (1)
2. Gamete B ✓ (1)

1.5.2

1. F ✓ – Acrosome ✓ (2)
2. H ✓ – Middle piece ✓/ Neck (2)

1.5.3

1. Zygote ✓ (1)
2. Fertilisation ✓ (1)

1.5.4 Gamete A ✓ (1)
TOTAL SECTION A: 50

SECTION B
QUESTION 2
2.1
2.1.1 Anaphase 1 ✓ (1)
2.1.2 Migration of full chromosomes to opposite poles. ✓ (1)
2.1.3

1. Homologous pair of chromosomes ✓/bivalent (1)
2. Crossing over ✓ (1)

2.1.4

• Homologous pair separate ✓ and
• full chromosomes migrate to the opposite poles. ✓
• In this way, the halving effect of meiosis ✓
• overcomes the doubling effect of fertilisation ✓/ chromosome number is reduced to half ✓
• Thus, maintaining a constant chromosome number from generation to generation.✓ (Max. 3) (3)

2.2
2.2.1

1. Plant A – Genotype: DdEe ✓; Phenotype: Long purple ✓ (2)
2. Plant B – Genotype: ddee ✓; Phenotype: Round red ✓ (2)

2.2.2

1. Plant A – 4 ✓ types (1)
2. Plant B – 1 ✓ type (1)

2.2.3

1. DE; De; dE; de ✓✓ (2)
2. de ✓ (1)

2.3
2.3.1 Short-sightedness ✓/ Myopia (1)
2.3.2 The image falls in front of the retina. ✓ (1)
2.3.3

• The eyeball being too long ✓
• The inability of the lens of the eye to become flat enough ✓ (less convex)
• Hence, the image of distant object is not clearly focused on the retina ✓ / The best image is formed in front of the retina. (3)

2.3.4 Person affected cannot see distant objects clearly. ✓ (1)
2.3.5 By wearing glasses with concave lenses. ✓ (1)
2.3.6

• When the optic nerve is damaged, the transmission of impulses ✓
• to the cerebral cortex/cerebrum ✓ is reduced or completely halted ✓
• hence, image formed on the retina is not interpreted. ✓ (Any 3) (3)

2.4 

2.5
2.5.1 27 ✓ days (1)
2.5.2 12^th ✓day of the cycle. (1)
2.5.3 The concentration of LH had reached its highest level on that day. ✓ (1)
2.5.4

• The progesterone levels are very low. ✓
• Oestrogen levels are very low. ✓
• FSH is high. ✓ (3)

2.5.5

• When the concentration levels of FSH is high, ✓ the concentration of progesterone is low. ✓
  OR
• When the concentration levels of progesterone is high, ✓ the concentration of FSH is low. ✓ (2)

[40]

QUESTION 3
3.1
3.1.1 100 ✓ Women (1)
3.1.2

1. Age of women ✓ (1)
2. Percentage / incidence of miscarriage ✓ (1)

3.1.3 The older the woman, ✓ the higher the chances of having a miscarriage. ✓ (2)
3.1.4

• By taking larger samples. ✓
• Repeat the investigation in different population areas. ✓ (2)

3.1.5 50% x 20 ✓ = 10 ✓
OR
 50  × 20 ✓=10 ✓ (2)
100
3.2
3.2.1 2 ✓ (1)
3.2.2

1. X^HX^h ✓✓ (2)
2. X^hX^h ✓✓ (2)

3.2.3

• Since the allele is found only on the X-chromosome ✓
• a male only has one allele ✓
• that is either dominant (normal) or ✓
• recessive (colour blind) ✓
• and therefore will always be colour blind ✓ (if recessive allele inherited) (Max. 4) (4)

3.2.4 100% ✓✓ (2)
3.3
3.3.1
B – Tympanic membrane ✓
D – Semi-circular canal ✓
F – Cochlea ✓ (3)
3.3.2 C – amplifies sound vibration  / transmits sound vibration from outer ear to inner ear. (1)
3.3.3 F ✓ (1)
3.3.4

• Mucus will block the opening of the eustachian tube ✓
• Air cannot enter or leave the middle ear ✓
• to equalise pressure / causing imbalance in pressure ✓
  OR
• Mucus may move through the eustachian tube ✓
• causing pressure in the middle ear ✓
• pushing on the tympanic membrane / part B. ✓(3)

3.3.5

• The sensory impulses✓
• from the cristae and maculae ✓
• will not be transmitted to the cerebellum ✓
• and therefore, maintenance of balance will be compromised. ✓
  (Max. 2)
  OR
• The sensory impulses ✓
• from the organ of Corti ✓
• will not be conveyed to cerebral cortex/cerebrum ✓ for interpretation
• and therefore, no hearing is possible. ✓
  (Max. 2) (2)

3.4
3.4.1

1. Cloning:
   • Process by which genetically identical individuals are formed.✓ (1)
2. Stem cells:
   • Are undifferentiated or unspecialised cells ✓ which can give rise to any of the other cells of the same organism. ✓ (Any 1) (1)

3.4.2

1.  
   • Molecular cloning ✓
   • Cell cloning ✓
   • Organism cloning ✓ (3)
2.  
   • Embryos ✓
   • Blood from placenta and umbilical cord ✓ (Any 1) (1)

3.4.3

• In order to increase the productivity and profit ✓ animals that produce large amounts of milk are carefully selected and cloned ✓/ high yield of milk.
• Hence the quality of herd is improved faster ✓ than the traditional way of breeding. (Max. 2) (2)

3.4.4

• Embryos are cloned in order to maintain a steady supply of stem cells for research purpose. ✓
• This enables researchers and research institutions to be self-sufficient in terms of the availability of stem cells. ✓
  (2)

[40]
TOTAL SECTION B: 80

SECTION C
QUESTION 4

Protein synthesis
Transcription ✓

• DNA double helix unwinds ✓
• weak hydrogen bonds of DNA break ✓
• forming two single strands of DNA ✓
• One strand acts as template ✓
• to form a complementary strand which is mRNA ✓/ (A – U; G – C )
• using free RNA nucleotides from the nucleoplasm ✓
• Three adjacent bases on mRNA make up a codon ✓
• which codes for an amino acid. ✓
• mRNA moves out of the nucleus ✓
• through the nuclear pore ✓
• into the cytoplasm ✓
• where it attaches to a ribosome ✓ (Max. 7)(7)

Translation ✓

• according to the codons of mRNA ✓
• t-RNA molecules with complementary anticodons ✓
• bring the required amino acids to the ribosome ✓
• The amino acids link together by peptide bond ✓
• to form the required proteins. ✓ (Max. 4) (4)

DNA replication ✓

• DNA double helix unwinds ✓
• weak hydrogen bonds between nitrogenous bases break ✓
• and the two DNA strands unzip/separate ✓
• Each original DNA strand serves as template to form a new strand ✓
• by attaching to free nucleotides from nucleoplasm ✓
• to form complementary strands ✓
• Each DNA molecule now consists of one original strand and one new strand. ✓
• The result is two genetically identical DNA molecules. ✓ (Max. 6) (6)

Assessing the presentation of the essay

Content:(17)
Synthesis:(3)

TOTAL SECTION C:20
GRAND TOTAL:150