PRINCIPLES RELATED TO MARKING LIFE SCIENCES

1. If more information than marks allocated is given
   Stop marking when maximum marks is reached and put a wavy line and ‘max’ in the right-hand margin.
2. If, for example, three reasons are required and five are given
   Mark the first three irrespective of whether all or some are correct/incorrect.
3. If whole process is given when only a part of it is required
   Read all and credit the relevant parts.
4. If comparisons are asked for but descriptions are given
   Accept if the differences/similarities are clear.
5. If tabulation is required but paragraphs are given
   Candidates will lose marks for not tabulating.
6. If diagrams are given with annotations when descriptions are required
   Candidates will lose marks.
7. If flow charts are given instead of descriptions
   Candidates will lose marks.
8. If sequence is muddled and links do not make sense
   Where sequence and links are correct, credit.
   Where sequence and links are incorrect, do not credit.
   If sequence and links become correct again, resume credit.
9. Non-recognised abbreviations
   Accept if first defined in answer.
   If not defined, do not credit the unrecognised abbreviation but credit the rest of the answer if correct.
10. Wrong numbering
    If answer fits into the correct sequence of questions but the wrong number is given, it is acceptable.
11. If language used changes the intended meaning
    Do not accept.
12. Spelling errors
    If recognisable, accept the answer, provided it does not mean something else in Life Sciences or if it is out of context.
13. If common names are given in terminology
    Accept, provided it was accepted at the memo discussion meeting.
14. If only the letter is asked for but only the name is given (and vice versa)
    Do not credit.
15. If units are not given in measurements
    Candidates will lose marks. Marking guideline will allocate marks for units separately.
16. Be sensitive to the sense of an answer, which may be stated in a different way.
17. Caption
    All illustrations (diagrams, graphs, tables, etc.) must have a caption.
18. Code-switching of official languages (terms and concepts)
    A single word or two that appear(s) in any official language other than the learners' assessment language used to the greatest extent in his/her answers should be credited if it is correct. A marker that is proficient in the relevant official language should be consulted. This is applicable to all official languages.

MEMORANDUM

SECTION A
QUESTION 1
1.1
1.1.1 B ✔✔
1.1.2 A ✔✔
1.1.3 B ✔✔
1.1.4 A ✔✔
1.1.5 B ✔✔
1.1.6 C ✔✔
1.1.7 C ✔✔
1.1.8 D ✔✔
1.1.9 D ✔✔
1.1.10 C ✔✔ (10 x 2) (20)
1.2
1.2.1 Homozygous ✔
1.2.2 (Gregor) Mendel ✔
1.2.3 Reproductive isolating mechanisms ✔
1.2.4 Stem cells ✔
1.2.5 Double helix ✔
1.2.6 Interphase ✔
1.2.7 Prognathous ✔
1.2.8 Down Syndrome ✔/ Trisomy 21 (8)
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 Meiosis ✔ (1)
1.4.2

1. Crossing over ✔ (1)
2. testis ✔ / testicle (1)

1.4.3

1. A – Chromatid ✔ (1)
2. B – Centromere ✔ (1) 
3. C – Homologous chromosomes / pair / bivalents ✔ (1)
4. D – Centriole ✔/ centrosome (1)

1.4.4

1. Metaphase I ✔ (1)
2. Anaphase II ✔ (1)

1.4.5 TWO ✔/2 (1)
1.5
1.5.1 Two characteristics ✔ are involved in the cross (1)
1.5.2 BbHh ✔ (1)
1.5.3

1. Bbhh ✔ (1)
2. Black, horned ✔ (1)

1.5.4 8 ✔✔ (2)
TOTAL SECTION A: 50

QUESTION 2
2.1
2.1.1 Protein synthesis ✔ (1)
2.1.2

1. mRNA ✔/ messenger RNA (1) 
2. Ribosome ✔ (1)
3. Nuclear membrane ✔ (1)

2.1.3 A G U ✔ (1)
2.1.4 S – R – P – Q ✔✔ (2)
2.1.5 Cytoplasm ✔ (1)
2.1.6

• The DNA molecule unwinds ✔
• and unzips / weak hydrogen bonds break ✔
• one side of the DNA molecule forms a template ✔
• free floating RNA nucleotides from the nucleolus ✔
• join to their complementary base pairs ✔ (T-A; C-G)
•  to form a new strand of mRNA ✔ (Any 5 x 1) (5)

2.1.7

• If nitrogenous base A was replaced by G it would mean that the codon would change to AGC ✔
• which may code for a different anticodon ✔/ UCA instead of AGU
• and a different amino acid ✔
• which may change the protein formed ✔ (4)

2.2
2.2.1 A sudden change in the DNA sequence ✔/ structure of a gene leading to altered characteristics. (1)
2.2.2 Pedigree ✔ diagram (1)
2.2.3 3 ✔ (1)
2.2.4

• Individual 8/13/15 has the disease ✔
• therefore his/her parents must both be carriers of the disease ✔
•  but they do not express the characteristic ✔
• therefore, it must be recessive (3)

2.2.5

Fertilisation
F1

Phenotype 3 Normal and 1 cystic fibrosis
They have a 25% ✔* chance of having a child with cystic fibrosis

• P1 and F1 ✔
  Meiosis and fertilisation ✔              (1* compulsory + Any 5) (6)

2.3.1 Any disease or abnormal condition that is determined by a gene/allele that is carried on the gonosomes ✔/ sex chromosomes / X or Y chromosomes. (1) 2.3.2 At the age of 3 ✔years (old) (1)
2.3.3

• The gene is found on the X chromosome ✔
• Boys only have one X chromosome ✔
• If that X chromosome carries the Duchenne’s gene ✔
• the boy will have Duchenne’s muscular dystrophy ✔
•  as there is no other allele to mask it. ✔ (Any 4 x 1) (4)

2.4
2.4.1 Cloning ✔ (1)
2.4.2

• Allows people to produce organisms with selected beneficial traits ✔
• Animals in danger of extinction could be saved. ✔
• Production of organs ✔ for transplants
  Mark first TWO only (Any 2 x 1) (2)

2.4.3

• A diploid cell ✔ / a cell with all the genetic information is needed - as a gamete is a haploid cell ✔ / only contains half the genetic information (2) [40]

QUESTION 3
3.1
3.1.1 A and C ✔✔ (2)
3.1.2

• Organisms that have similarities in the structure ✔
•  indicates common ancestry ✔ (2)

3.1.3

• Fossil record ✔
• Biogeography ✔
• Genetics ✔
  Mark first TWO only (Any 2 x 1) (2)

3.2 3.2.1

• Random arrangement of chromosomes ✔ OR Meiosis ✔
• crossing over ✔
• random mating ✔
• random fertilisation ✔
• mutations ✔
  Mark first THREE only (Any 3 x 1) (3)

3.2.2

• The deer are either black or white. ✔
• There is no intermediate characteristic ✔/ grey (2)

3.2.3

Mark first TWO only Table ✔ + Any 4 (5)
3.3

• The common ancestor ✔original baobab population
• was separated ✔into different populations
• by the sea ✔*/ due to continental drift
• There was no gene flow ✔ between the populations
• Each population was exposed to different environmental conditions ✔/ different selection pressures.
• Natural selection occurred independently ✔ in each population.
• the individuals in the two populations became different ✔from each other over time
• genotypically and phenotypically ✔
• Even if the two are to mix again ✔
• they will not be able to interbreed ✔
• forming different baobab species (1* compulsory + Any 5)(6)

3.4
3.4.1

• Breed of dog ✔
• Genetic disease ✔
  Mark first TWO only (2)

3.4.2 Percentage of mixed breed dogs with cataracts

•  (2)

3.4.3 Pure breed dogs suffer from genetic diseases more than mixed breed dogs ✔✔ (2)
3.4.4

Marking guideline: 

(6)
3.4.5 Natural selection takes place due to selective pressure of the environment. ✔/Individuals with characteristics that help them to survive in nature are selected.
In artificial selection humans are the selective pressure. ✔/ The characteristics that are selected is what humans want/not necessarily helping them to survive. (2)
3.4.6 All dogs are able to interbreed ✔ and produce fertile offspring. ✔ (2)
3.4.7 It is not ethically correct ✔ as more artificially bred / pure breed dogs suffer from genetic diseases than mixed breed dogs. ✔ (2) [40]
TOTAL SECTION B: 80

SECTION C
QUESTION 4
Changes in the skull and parts of the skeleton that support bipedalism:

• The foramen magnum has moved to the base of the skull ✔ so that the head can be held vertically. ✔ / spinal cord can be in line with the brain
• The position of the pelvic girdle moved to under / the bottom of the core body ✔ so it is suitable to carry the weight of the upper body ✔
• The pelvis has become more cup shaped / wider and shorter ✔ which makes it suitable to carry the core / weight of the upper body ✔
• The vertebral column changed from C-shape to S-shaped ✔ / greater lumber curvature in spine for better balance ✔ / support of upper body weight
  (Any 3 x 2) (6)

Changes in skull that support change in diet:

• Reduction in the size of teeth ✔/ canines ✔
• Reduction in jaw size ✔
• Reduction of cranial brow ridges ✔
• and cranial ridges ✔due to
• smaller muscles for chewing✔
• Indicate that modern humans changed from a diet of raw food ✔ to ∙ a diet of softer/ cooked food ✔
• that does not require the same amount of chewing ✔/ tearing / biting (Any 6 x 1) (6)

Changes in the skull that support improved communication and use of tools:

• a larger cranium ✔
• indicated a larger brain size ✔
• which can process a larger amount of information ✔
• at a faster speed ✔
• This has led to the development artificial language ✔ for communication
• And the invention / greater use of tools and weapons ✔
  (Any 5 x 1) (5)

ASSESSING THE PRESENTATION OF THE ESSAY

Content (17)
Synthesis (3)

TOTAL SECTION C: 20
GRAND TOTAL: 150