NATIONAL
SENIOR CERTIFICATE
GRADE 12
JUNE 2022
LIFE SCIENCES
MARKING GUIDELINE
MARKS: 150

SECTION A

QUESTION 1

1.1

1.1.1 D ✓✓
1.1.2 B ✓✓
1.1.3 A ✓✓
1.1.4 A ✓✓
1.1.5 C ✓✓
1.1.6 B ✓✓
1.1.7 A ✓✓
1.1.8 C ✓✓
1.1.9 A ✓✓
1.1.10 C ✓✓   (10 x 2) (20)

1.2

1.2.1 Internal ✓ fertilisation
1.2.2 Umbilical vein ✓
1.2.3 Mitochondrion ✓/Mitochondria
1.2.4 Pinna ✓
1.2.5 Acrosome ✓
1.2.6 Puberty ✓
1.2.7 Chromatin ✓ network
1.2.8 Amniotic ✓egg (8 x 1) (8)

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 DNA profiling ✓ (1)
1.4.2 Adult C ✓ (1)
1.4.3 

  • All bands of adult B and C together ✓
  • match all the children’s bands ✓
    OR
  • He is the only adult that can provide all the DNA bands ✓ with adult B that the children have ✓ (2)

1.4.4

  • Child 1 and 2 ✓✓ (2)

1.4.5

  • Tracing missing persons ✓
  • Identify crime suspects ✓
  • Identification of genetic disorders ✓
  • Establishing family relations ✓
  • Matching tissues for organ transplants ✓
  • Identifying dead persons ✓/animals
    (Mark first TWO only) (2)

1.5

1.5.1 

  1. Dihybrid cross ✓ (1)
  2. Involves the inheritance of two characteristics ✓ (1)

1.5.2   1 ✓ (1)
1.5.3    FfBb ✓ (1)
1.5.4

  1. Fluffy tails and brown fur ✓ (1)
  2. ffBb ✓ (1)

1.5.5 12/16  ✓✓ OR ¾ OR 75% (2)
TOTAL SECTION A: 50

QUESTION 2

2.1

2.1.1

  1. Deoxyribose ✓ (1)
  2. Nucleotide ✓ (1)

2.1.2 

  • The DNA (double helix) unwinds✓and
  • unzips ✓/hydrogen bonds break
  • to form two separate strands ✓
  • Both DNA strands serve as templates ✓
  • to build a complementary DNA ✓/(A to T and C to G) using free (DNA) nucleotides from the nucleoplasm
  • This results in two identical (DNA) molecules ✓
  • Each molecule consists of one original strand and one new strand ✓             (Any 6 x 1) (6)

2.1.3 Met ✓- Phe ✓- Cys ✓ (3)
2.1.4

  • Codon AUG (on the mRNA) changed to AAG ✓
  • Anticodon UAC (on tRNA) changed to UUC ✓
  • which resulted in Lys ✓ being picked by tRNA and
  • a different protein was formed ✓ (4)

2.2.1 

  1. Locus ✓ (1)
  2. Centromere ✓ (1)

2.2.2 Heterozygous ✓ (1)
2.2.3 The alleles/letters representing the gene are different. ✓ (1)
2.2.4
Similarity:

  • They carry the same genes at the same loci ✓/positions/locations

Difference:

  • They carry different alleles ✓
  • because of crossing over ✓ during meiosis and
  • mutations ✓/copying errors during DNA replication
    1 similarity + Any 2 differences (3)

2.3

2.3.1

  1. Zygote ✓ (1)
  2. Morula ✓/ Blastula (1)

2.3.2 Fertilisation ✓ (1)
2.3.3 In the fallopian tubes ✓/Oviducts (1)
2.3.4

  • The process is oogenesis ✓
  • Diploid cells in the ovary undergo mitosis ✓
  • to form numerous follicles ✓
  • At the onset of puberty ✓
  • and under the influence of FSH ✓
  • one cell inside a follicle enlarges and undergoes meiosis ✓
  • Of the four cells that are produced, only one survives ✓
  • to form a mature, haploid ovum ✓ (Any 6 x 1) (6)

2.3.5

  •  Amniotic fluid acts as a shock absorber and protect the foetus from mechanical injury ✓ /temperature changes/dehydration
  • The placenta serves as a barrier protecting the foetus from certain diseases ✓ (2)

2.4

LS June 2022 Grade 12 Ans 2 4
*1 Compulsory + Any 5 (6)

2.5.1 Karyotype ✓ (1)
2.5.2 Autosomes ✓ (1)
2.5.3 Female ✓ (1)
2.5.4

  • The last pair ✓/chromosome pair 23/gonosomes
  • consist of two X chromosomes ✓/XX (2)

2.5.5 

  • During Anaphase ✓ I/II
  • Chromosome pair 21/chromosome failed to separate ✓/ nondisjunction occurred at position 21
  • Resulting in a gamete (daughter cell) with an extra chromosome ✓ at position 21
  • When this gamete was fertilised by a normal gamete ✓
  • The zygote ended up with 3 chromosomes at position 21 ✓ (5)
    [50]

QUESTION 3

3.1

3.1.1 

  1. Centriole ✓/ Centrosome (1)
  2. Spindle fibre ✓ (1)

3.1.2 Anaphase I ✓ (1)
3.1.3 Each chromosome of each homologous pair is being pulled to the opposite poles ✓ (1)
3.1.4    3 ✓ (1)
3.1.5

  • The chromosomes show swapped segments of genetic material ✓ (1)

3.1.6

  • Introduces genetic variation ✓ in offspring thereby
  • improving the chances of survival ✓ (2)

3.2

3.2.1 

  1. Menstruation ✓ (1)
  2. Ovulation ✓ (1)

3.2.2

  1. Follicle stimulating hormone ✓/FSH (1)
  2. Progesterone ✓ (1)

3.2.3

  • Stimulates the development of primary follicles into mature Graafian follicle ✓ (1)

3.2.4

  • The endometrial lining will no longer be maintained ✓
  • This will result in the lining being broken down and shed ✓ during menstruation ✓
  • preventing possible implantation of the fertilised egg ✓ and pregnancy ✓
  • new follicle ✓ being formed (Any 5 x 1) (5)

3.3

3.3.1 

  1. D ✓– Eustachian tube ✓ (2)
  2. E ✓– Round window ✓ (2)

3.3.2 Transmits sound vibrations to the middle ear. ✓ (1)
3.3.3

  • They lie on three different planes ✓
  • to detect movement in any direction ✓
  • fluid moves in at least one of the semi-circular canals ✓
  • to stimulate receptors ✓                     (Any 3 x 1) (3)

3.4

  • The receptor receives the stimulus ✓ and
  • converts it into an impulse ✓
  • which is transmitted by the sensory neuron ✓
  • through the dorsal root ✓
  • of the spinal nerve ✓
  • to the spinal cord ✓
  • where the impulse is transferred via the interneuron ✓
  • to the motor neuron ✓
  • which carries the impulse via the ventral root ✓
  • to the effector ✓/muscle/gland
  • The impulse is transferred from one neuron to the next via a synapse ✓
    (Any 7 x 1) (7)

3.5

3.5.1 X = 292 + 301 + 297
                          3
              = 297 ✓mm ✓ (Accept 296,67/ 296,7) (3)
3.5.2

  1. Accommodation ✓ (1)
  2.  
    • Ciliary muscles contract ✓
    • Suspensory ligaments slacken ✓/loosen
    • Tension on the lens decreases ✓
    • Lens becomes more convex ✓/more rounded/bulging
    • Light rays are focused on the retina ✓ (5 x 1) (5)

3.5.3

LS June 2022 Grade 12 Ans 3 5(6)
Guideline for assessing the graph

 CRITERIA   ELABORTION   MARK 
 Correct type of graph  (T)   Bar graph drawn   1
 Caption of graph (C)   Both variables included    1
 Axes labels (L)   X- and Y-axis correctly labelled   1
 Scale for X-and Y - axis(S) 
  • Equal space between bars and width of bars for X-axis and
  • Correct scale for Y-axis
  1
 Plotting of bars (P)
  • 1 to 2 bars plotted correctly
  • All 3 bars plotted correctly
  1
  2

 

3.5.4 As the age of the volunteers increase, the longer is the average focusing distance. ✓✓
OR
As the age of the volunteers decreases, the shorter is the average focusing distance ✓✓ (2)
[50]
TOTAL SECTION B: 100
GRAND TOTAL: 150

Last modified on Thursday, 15 December 2022 12:25