Life Sciences Paper 2: prelim revision

At a glance

This guide follows the Gauteng Department of Education and Sci-Bono Life Sciences Grade 12 Paper 2 revision broadcast of 17 September 2026, presented the afternoon before the prelim. It covers the four Paper 2 topics in the order the presenters taught them: the two big topics first (evolution and genetics), then DNA and meiosis. The broadcast did not re-teach everything. It concentrated on the sub-topics learners find hardest and on how the marks are awarded.

Topic	Term	%	Marks	What the broadcast stressed
DNA: code of life	1	18	27	DNA vs RNA, replication and protein synthesis by heart, mutation reasoning, DNA profiles
Meiosis	1	14	21	Terminology (Question 1.2), phases from diagrams, crossing over, non-disjunction and Down syndrome
Genetics and inheritance	1 and 2	32	48	Genetic cross layout, co-dominance, dihybrid tables, sex-linked reasoning, blood groups, pedigrees
Evolution	3	36	54	Guideline wording for Darwin and speciation, Lamarck applied to a scenario, human evolution, Out of Africa
Total		100	150	2 hours 30 minutes. Bring a ruler, calculator, pencil and protractor.

The single most repeated instruction in the broadcast: go to the Examination Guidelines and learn the processes in their wording. Where the guideline gives a list of bullets (Darwin, speciation, replication, transcription, translation), write those bullets in that order.

How the marks are earned

• Generic versus applied. If the question asks how Darwin (or speciation) works in general, write the guideline bullets as they stand. If you are given an example (wolves, ratites, stickleback fish), put the example into every bullet.
• Say "population", not "species", at the start of a speciation answer. Speciation is the formation of new species, so you cannot start with species. Start with a population and end with "the two populations are now different species". That closing sentence can be a compulsory mark.
• Say "allele", not "characteristic", when offspring inherit something. "They pass on the allele for immunity" tells the marker you know it is genetic.
• Tables are marked for being tables. Rule horizontal and vertical lines, give column headings, and compare like with like on each row.
• Genetic crosses carry three free marks: P₁ and F₁ written in the right place, meiosis and fertilisation written in the right place, and the parents' phenotypes copied from the question. See the genetic cross section.
• Genotypes are written together, no spaces or commas: FfHh, not Ff, Hh. Most genotype answers are worth 2 marks.
• Follow the instruction word. Give a letter when asked for a letter, a name when asked for a name. "Share" means similarities. "Observable" means only what you can see in the diagram.
• Scientific names: genus with a capital, species with a small letter, both underlined when handwritten (Homo sapiens). "sapiens" alone is not a scientific name.
• Proportions: if the question says percentage or ratio, give that form. It can be a compulsory mark.
• "Mark first TWO only": if two reasons are asked, the first two you write are marked. Start with the one you are surest of.

Evolution (54 marks)

The guideline lists the ideas about origins in the order they arose: Lamarckism, Darwinism, Punctuated Equilibrium.

Lamarckism (Jean Baptiste de Lamarck, 1744 to 1829)

Lamarck explained evolution with two "laws". Learn the names and how to describe them.

1. The law of use and disuse. If an organism uses a structure or organ more regularly, it becomes better developed or enlarged (the use part). If an organism does not use a structure or organ frequently, it becomes less developed or reduced in size and may disappear altogether (the disuse part). Give both parts.
2. The law of the inheritance of acquired characteristics. Characteristics developed during the life of an individual (acquired characteristics) can be passed on to the offspring.

Why Lamarck's theory was rejected

• There is no evidence that acquired characteristics are inherited by offspring.
• An organism cannot change its DNA.
• According to Mendel, it is the genotype that determines the phenotype, not the other way around.

Applying Lamarck to a scenario: the stickleback fish

A Lamarck answer always starts with all the organisms being the same. There is no variation in Lamarck; variation is Darwin. Then trace the two laws through the example.

Show memo: How would Lamarck have explained the absence of spiky fins on stickleback fish in lakes? (4)

• All stickleback fish had spiky fins ✓ originally
• In the lakes there were fewer / no predators ✓
• The fish did not use the spiky fins anymore ✓ / they used their fins less and their spikes disappeared ✓
• The acquired characteristic of no spikes was then passed on to the next generation ✓
• Eventually all the fish had no spikes ✓

Darwinism: natural selection (Charles Darwin, 1809 to 1882)

The generic answer, in the guideline's order. Learn it word for word.

1. There is a great deal of variation amongst the offspring.
2. Some have favourable characteristics and some do not.
3. When there is a change in the environmental conditions or if there is competition,
4. then organisms with characteristics which make them more suited, survive,
5. whilst organisms with unfavourable characteristics, which make them less suited, die.
6. The organisms that survive, reproduce
7. and thus pass on the allele for the favourable characteristic to their offspring.
8. The next generation will therefore have a higher proportion of individuals with the favourable characteristic.

The first bullet (variation) and the last (higher proportion in the next generation) are the ones learners drop. Always open with variation and always close with what happens to the population.

Applying Darwin: wolves at Chernobyl

Show memo: Use Darwin's theory of natural selection to explain the development of immunity to cancer in these wolves.

• There was variation amongst (the population of) the wolves ✓
• Some had the mutation which made them immune to cancer and some did not ✓
• When exposed to radiation
• the wolves without the mutation / immunity died ✓
• Those with the mutation / immunity survived ✓
• and reproduced ✓
• passing the allele for the mutation / immunity to their offspring ✓
• The next generation had a higher proportion of wolves with the mutation ✓ / immunity to cancer

Punctuated equilibrium (Eldredge and Gould, 1972)

• Punctuated equilibrium explains the speed at which evolution takes place.
• Evolution involves long periods of time where species undergo little or no change (known as equilibrium).
• This alternates with (is punctuated by) short periods of time where rapid changes occur through natural selection, during which new species may form in a short period of time.

Know the names and the year. On a phylogenetic tree, sharp right-angled branching with long straight lines shows punctuated equilibrium; gradual sloping branches show gradualism.

Natural selection versus artificial selection

Natural selection	Artificial selection
The environment or nature is the selective force (who selects)	Humans are the selective force
Selection is in response to suitability to the environment	Selection is in response to satisfying human needs
Occurs within a species	May involve one or more species (as in cross breeding)

Formation of new species

Biological species concept: a group of organisms with similar characteristics that are capable of interbreeding to produce fertile offspring. All three parts must be in your definition.

Speciation through geographic isolation (guideline bullets, learn in order):

1. If a population of a single species becomes separated by a geographical barrier (sea, river, mountain, lake)
2. then the population splits into two.
3. There is now no gene flow between the two populations.
4. Since each population may be exposed to different environmental conditions / the selection pressure may be different,
5. natural selection occurs independently in each of the two populations,
6. such that the individuals of the two populations become very different from each other
7. genotypically and phenotypically.
8. Even if the two populations were to mix again, they will not be able to interbreed.
9. The two populations are now different species.

Do not explain natural selection again inside bullet 5. "Natural selection occurs independently" is the whole mark. Examples you must be able to apply one of: Galapagos finches, Galapagos tortoises, plants on different land masses linked to continental drift (baobabs in Africa and Madagascar, proteas in South Africa and Australia), or any mammals on different land masses.

Mechanisms of reproductive isolation

Mechanism	Example
Breeding at different times of the year	Two mayfly species emerge in different weeks of spring; two butterfly species breed March to June and July to November
Species-specific courtship behaviour	Two similar bird species have different mating rituals
Adaptation to different pollinators	Two orchid species with different nectar tube lengths are pollinated by different moth species
Infertile offspring	Donkey × horse gives a sterile mule; two frog species mated in a lab give viable but sterile offspring
Prevention of fertilisation	Different or specialised genitalia

Worked example: breeding months in ratites (DBE November 2025)

Show memo: explain why the ostrich and the emu are different species

They breed at different times of the year: ostriches lay eggs in September, while emus lay their eggs from November to April ✓ (cause). Therefore they cannot interbreed ✓ (effect).

Show memo: describe how the evidence (biogeography) supports the theory of evolution (5)

The ratites all had one common ancestor ✓. When continental drift took place ✓ the population of ratites was separated ✓. The sub-populations were faced with different environmental conditions ✓ and underwent natural selection independently ✓ to form different species ✓.

The presenter's markers: you must say common, population, independently and different.

Human evolution

Similarities between humans and African apes

• Upright posture
• Large brain relative to body mass
• Longer upper arm
• Eyes face forward (binocular vision)
• Eyes contain cones for colour vision (not "rods and cones")
• Poor sense of smell (olfactory brain centres reduced)
• Only two mammary glands
• Freely rotating arms: rotation around the elbow joints and wrist joints
• Bare fingertips / nails instead of claws; fingerprints
• Opposable thumbs (precision grip); five digits per limb

Differences between humans and African apes

Feature	Humans	African apes
Locomotion	Bipedalism	Quadrupedalism
Foramen magnum	In a (more) forward position	Towards the back of the skull
Spine	S-shaped	C-shaped
Pelvic girdle	Shorter and wider	Longer and narrower
Cranium size	Larger	Smaller
Palate shape	Semi-circular (rounded, C-shaped, parabolic)	Rectangular (U-shaped)
Dentition	No gaps between teeth; smaller canines	Gaps between teeth (diastema); larger canines
Face	Non-prognathous: flat face	Prognathous: sloped face
Cranial and brow ridges	Absent	Present

Use these exact terms. The foramen magnum is "in a more forward position", never "under" or "below". The pelvis is "short and wide", not "small" or "slim".

Our place in the animal kingdom

Domain Eukarya, Kingdom Animalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo, Species Homo sapiens.

Phylogenetic trees

A phylogenetic tree is a schematic form that shows the evolutionary relationships within a set of organisms or groups of organisms. Do not confuse it with a pedigree diagram, which shows the genetic relationships between close family members.

From a tree you must be able to read: who the common ancestor is, which species are extinct, when a species originated, how long it lived and when it became extinct. Trees can run bottom to top, left to right or right to left, so find the common ancestor first.

Two species are most closely related if they share the most recent common ancestor (the branch point nearest the tips).

Evidence for a common ancestor of all hominids

• Fossil evidence: know each fossil, where it was found, by whom, when, and its characteristics.
• Genetic evidence: mitochondrial DNA.
• Cultural evidence: stone tools. Homo habilis ("handy man") made the first simple tools; tools became more complex as brains grew.

Out of Africa hypothesis: the fossil answer

• Ardipithecus fossils were found in Africa only ✓
• Australopithecus fossils were found in Africa only ✓
• Fossils of Homo habilis were found in Africa only ✓
• The oldest fossils of Homo sapiens were found in Africa ✓
• The younger fossils of Homo sapiens were found in other parts of the world ✓

For Homo erectus: the oldest fossils were found in Africa ✓, the younger fossils in other parts of the world / Asia ✓, indicating that Homo erectus migrated out of Africa ✓.

Brain volume and tools

H. sapiens have a bigger brain volume than H. habilis ✓, therefore H. sapiens are more intelligent ✓, leading to H. sapiens developing more complex / more specialised tools ✓. Start from brain size, go to intelligence, end at tools.

Genetics and inheritance (48 marks)

Concepts learners confuse

Term	Meaning	Versus	Meaning
Chromatin	The uncoiled network of DNA and protein in a non-dividing nucleus	Chromosome	The condensed, visible thread of DNA and protein during division
Gene	A section of DNA that codes for a characteristic	Allele	One of the alternative forms of a gene
Dominant allele	Expressed whenever it is present	Recessive allele	Expressed only when no dominant allele is present (homozygous)
Phenotype	The visible trait, e.g. tallness	Genotype	The genetic make-up, e.g. TT, Tt or tt
Homozygous	Two identical alleles (TT, tt)	Heterozygous	Two different alleles (Tt)

The layout of a genetic cross

P1   Phenotype   ........  x  ........   ✓  (copied from the question)
     Genotype    ........  x  ........   ✓
Meiosis
     Gametes     ........  x  ........   ✓
Fertilisation
F1   Genotype    ..........................  ✓
     Phenotype   ..........................  ✓
P1 and F1 ✓   Meiosis and fertilisation ✓   (marked where they appear, not at the bottom)

The alleles segregate during meiosis to form gametes; during fertilisation the individual gets one allele from each parent. A Punnet square is acceptable for the fertilisation step.

Three types of monohybrid cross

Type	What happens in the heterozygote	Example
Complete dominance	One allele is completely dominant; only the dominant trait shows	Tt is tall
Incomplete dominance	Neither allele is dominant; the heterozygote shows an intermediate (blend)	Red × white gives pink flowers
Co-dominance	Both alleles are expressed equally in the phenotype	Red-yellow apples; AB blood group

Caution: on air the two definitions were said the wrong way round (co-dominance called the intermediate, incomplete dominance called equal expression). The table above is correct, and the apple example the presenter then worked is co-dominance precisely because both colours are expressed equally.

Worked example: co-dominance in apples

P1   Phenotype   red-yellow  x  red-yellow   ✓
     Genotype        RY      x      RY       ✓
Meiosis
     G/gametes      R, Y     x     R, Y      ✓
Fertilisation
F1   Genotype    RR,   RY,   RY,   YY        ✓
     Phenotype   red   red-yellow   yellow   ✓
P1 and F1 ✓   Meiosis and fertilisation ✓    (any 6)

Both alleles are capitals because neither is dominant over the other. Half (50%) of the F₁ is red-yellow. To get only red-yellow apples, cross a tree with red apples (RR) with a tree with yellow apples (YY).

Dihybrid crosses

• Two traits are crossed ("di" means two; spell it dihybrid, not dyhybrid).
• Mendel's Law of Independent Assortment: the alleles of a gene for one characteristic segregate independently of the alleles of a gene for another characteristic. The genes are on different chromosomes.
• Heterozygous × heterozygous for both traits always gives the phenotypic ratio 9 : 3 : 3 : 1.
• You will not be asked to write out a full dihybrid cross, but you must read a 4 × 4 table and form gametes (FfHh gives FH, Fh, fH, fh).

Sex determination

Humans have 46 chromosomes (23 from each parent): 22 pairs of autosomes and 1 pair of sex chromosomes (gonosomes), pair 23. Males are XY, females XX. In a karyotype, the female's pair 23 match in size; the male's Y is smaller.

Males produce two kinds of sperm, half 22 + X and half 22 + Y, so there is always a 50% chance of a son and 50% of a daughter.

Sex-linked inheritance

• Genes located on a sex chromosome are sex-linked genes; in humans this usually means X-linked.
• Fathers pass X-linked alleles to their daughters but not their sons (sons get his Y).
• Mothers pass X-linked alleles to both sons and daughters.
• Males are more often affected by recessive X-linked traits: they have only one X, so there is no other allele to dominate over the recessive allele.

Show memo: A haemophilic female marries a normal male. Explain why all their sons will be haemophilic. (FS Nov 2022)

• An individual inherits one allele from each parent ✓
• The Y chromosome was inherited from the father ✓
• and the recessive allele was inherited from the mother ✓
• since the mother has two recessive alleles ✓
• A son only needs to get one recessive allele to be haemophiliac ✓
• since the Y chromosome does not carry any allele to mask the haemophilia allele ✓

Blood groups: multiple alleles

Blood group (phenotype)	Genotype	What it shows
A	IᴬIᴬ or Iᴬi	Complete dominance (Iᴬ over i)
B	IᴮIᴮ or Iᴮi	Complete dominance (Iᴮ over i)
AB	IᴬIᴮ	Co-dominance
O	ii	Recessive, homozygous

Three alleles, four blood groups. Use the capital I with superscripts only for blood groups; for any other trait use the letters the question gives you. Write the I clearly so it cannot be read as an L.

Pedigree diagrams

Read the stem first: Goltz syndrome is caused by a dominant allele on the X chromosome (Xᴳ). Circles are females, squares males; shaded is affected. Count carefully: children labelled "Female" count as females even though their circles are small.

Gabby is affected yet has unaffected children, so she must be heterozygous: XᴳXᵍ. Pilusa (XᴳY) and Anju (XᵍXᵍ): their sons get Y from Pilusa and Xᵍ from Anju, so every son is unaffected.

Biotechnology

Biotechnology is the use of biological processes, organisms or systems to improve the quality of human life. Genetic engineering, the manipulation of genes or DNA to produce organisms with desirable characteristics, is one way of achieving it. Know case studies on genetically modified organisms, stem cell research and cloning.

DNA: code of life (27 marks)

DNA and RNA

Know the structure, location and function of each. DNA carries the coded information for protein synthesis; RNA plays a role in protein synthesis. DNA is found in the nucleus and the mitochondria (and chloroplasts in plants). The structure of DNA was worked out by James Watson and Francis Crick, using the X-ray work of Rosalind Franklin and Maurice Wilkins. Use full names and surnames.

	DNA	RNA
Sugar	Deoxyribose	Ribose
Strands	Double stranded (double helix)	Single stranded
Length	Long	Short
Bases	A, T, C, G	A, U, C, G (uracil instead of thymine)
Monomer	Nucleotides	Nucleotides

A nucleotide is a phosphate, a sugar and a nitrogenous base. Complementary bases are joined by weak hydrogen bonds. The natural shape of DNA is a double helix; "double strand" may lose the mark.

Write the RNA types with a small first letter: mRNA, tRNA, rRNA.

DNA replication (learn by heart)

1. The double helix unwinds.
2. Weak hydrogen bonds between nitrogenous bases break and the two DNA strands unzip (separate).
3. Each original DNA strand serves as a template on which its complement is built.
4. Free nucleotides build a DNA strand onto each of the original two DNA strands by attaching to their complementary nitrogenous bases (A to T and C to G).
5. This results in two identical DNA molecules. Each molecule consists of one original strand and one new strand.

Replication takes place during interphase, so that the DNA can be shared equally between the daughter cells during cell division.

Protein synthesis (learn by heart)

Transcription (in the nucleus)

1. The double helix unwinds.
2. Weak hydrogen bonds between nitrogenous bases break and the two DNA strands unzip / separate.
3. One DNA strand acts as the template for the construction of mRNA.
4. Free RNA nucleotides from the nucleoplasm form mRNA,
5. so mRNA complements the DNA (A with U, C with G) in the nucleus.

Translation (at the ribosomes, in the cytoplasm)

6. The coded mRNA leaves the nucleus through the nuclear pore to the ribosome.
7. tRNA picks up amino acids and its anticodon complements the codon on the mRNA at the ribosome.
8. Amino acids bond by peptide bonds to form a protein.

Hydrogen bonds hold the bases together; peptide bonds join amino acids. Do not swap them.

Replication versus transcription

DNA replication	Transcription
Both strands act as templates	One strand acts as a template
Free DNA nucleotides from the nucleoplasm attach to each strand	Free RNA nucleotides from the nucleoplasm attach to the template strand
Complementary base pairing A-T and G-C	Complementary base pairing A-U and G-C
Two identical DNA molecules are formed	An mRNA molecule is formed

Mutations: explaining the effect on the protein

Work backwards from the tRNA anticodon to the mRNA codon to the DNA triplet: anticodon CCU, codon GGA, DNA CCT (proline); anticodon CGU, codon GCA, DNA CGT (arginine). Then write the chain of cause and effect:

• The sequence of bases on the DNA molecule changes ✓
• from CCT to CGT ✓ / the second base in the DNA triplet changed from C to G
• The codon GGA changed to GCA ✓
• The tRNA molecule with the anticodon CCU ✓
• is now replaced by a tRNA molecule with the anticodon CGU ✓
• The sequence of amino acids changes ✓ and
• a different protein is formed ✓

DNA profiles and DNA profiling

A DNA profile is a pattern of black bars that represents the DNA fragments of a person (say bars or bands, not lines or stripes). Each person's profile is unique, except identical twins. DNA profiling is the process that produces the profile. It is used for:

• paternity testing
• tracing missing persons and identifying dead persons
• identifying genetic disorders
• identifying criminals in forensic investigations
• establishing family relations
• matching tissues for organ transplants

Every band in a biological child must come from the mother or the father. Paternity testing uses both parents and the child; comparing the father and child alone is not reliable.

Why profiling can be controversial (mark first two only): samples may be planted / a person can be framed; human error or a very small sample can give false results, and private labs may not follow testing standards; invasion of privacy / revealing personal information.

Meiosis (21 marks)

• Meiosis is the type of cell division where a diploid cell undergoes two cell divisions to form four haploid cells (gametes).
• Before meiosis, DNA replication takes place (interphase), so each chromosome consists of two chromatids joined by a centromere.
• Meiosis I: one diploid cell gives rise to two haploid cells. Meiosis II: the two haploid cells divide to form four haploid cells or gametes.
• Biological importance: crossing over introduces genetic variation; meiosis ensures that sex cells have the haploid number of chromosomes, so the diploid number is restored at fertilisation.
• Meiosis happens in the ovaries and testes.

Terminology (usually Question 1.2)

Term	Meaning
Homologous chromosomes	A pair of chromosomes of the same size and shape carrying genes for the same characteristics, one from each parent
Bivalent	A pair of homologous chromosomes lying side by side in prophase I
Chromosome	A thread-like structure of DNA and protein that carries genes
Chromatids	The two identical threads of a replicated chromosome
Centromere	The region that holds two chromatids together and attaches to a spindle fibre
Centrosome	The region containing the centrioles, which forms the spindle in animal cells
Crossing over	The exchange of genetic material between non-sister chromatids of homologous chromosomes in prophase I
Chiasma (chiasmata)	The point where non-sister chromatids overlap and crossing over happens
Karyotype	The number and appearance of the chromosomes of an organism, arranged in homologous pairs
Non-disjunction	The failure of homologous chromosomes or chromatids to separate during anaphase
Karyokinesis	Division of the nucleus
Cytokinesis	Division of the cytoplasm

Centromere, centrosome and centriole are three different words. Read the question.

The phases

Phase	Meiosis I	Meiosis II
Prophase	Homologous chromosomes pair into bivalents; crossing over at chiasmata	Chromosomes (two chromatids each) condense; spindle forms
Metaphase	Homologous pairs line up at the equator (in pairs)	Single chromosomes line up at the equator
Anaphase	Homologous chromosomes separate; centromeres do not split; whole chromosomes move to opposite poles	Centromeres split; chromatids (daughter chromosomes) move to opposite poles
Telophase	Two haploid cells form	Four haploid cells form

Crossing over (3 marks)

Adjacent (non-sister) chromatids of homologous chromosomes overlap ✓ at points called chiasmata ✓. There is an exchange of genetic material ✓.

Non-disjunction and Down syndrome

• The spindle fibre fails to separate the chromosomes during meiosis.
• Members of one pair of homologous chromosomes fail to separate during anaphase I (or chromatids in anaphase II).
• Two gametes receive an extra copy of the affected chromosome; two gametes lack it.

Show memo: Describe how non-disjunction leads to Down syndrome. (5)

• Failure of homologous pair 21 / chromosome 21 to separate ✓
• during anaphase ✓ I / II
• leads to a gamete with 24 chromosomes ✓ / an extra chromosome
• The fertilisation of this gamete with a normal gamete ✓ / with 23 chromosomes
• results in a zygote with 47 chromosomes ✓ / an extra chromosome / trisomy 21

Focus on the extra copy of chromosome 21, not a missing one.

Confusable pairs

Pair	How to tell them apart
Lamarck vs Darwin	Lamarck: all the same at the start, change by use and disuse during life. Darwin: variation at the start, selection by the environment.
Species vs population	Speciation answers start with a population and end with different species.
Natural vs artificial selection	Environment vs humans; suitability vs human needs; within a species vs one or more species.
Phylogenetic tree vs pedigree diagram	Evolutionary relationships between groups vs genetic relationships in one family.
Incomplete dominance vs co-dominance	Intermediate blend (pink) vs both expressed equally (red-yellow, AB).
Gene vs allele	Section of DNA for a characteristic vs one form of that gene.
Genotype vs phenotype	Letters (Tt) vs appearance (tall).
Replication vs transcription	Both strands, DNA nucleotides, A-T, two DNA molecules vs one strand, RNA nucleotides, A-U, one mRNA.
Transcription vs translation	DNA to mRNA in the nucleus vs mRNA to protein at the ribosome.
Hydrogen bond vs peptide bond	Between bases vs between amino acids.
Codon vs anticodon	Triplet on mRNA vs triplet on tRNA.
DNA profile vs DNA profiling	The pattern of black bars vs the process.
Centromere vs centrosome vs centriole	Holds chromatids vs spindle-forming region vs the organelle within it.
Anaphase I vs anaphase II	Centromeres do not split, chromosomes move vs centromeres split, chromatids move.
Crossing over vs non-disjunction	Exchange of genetic material (variation) vs failure to separate (abnormal number).

What to watch in the broadcast

The broadcast is reliable on the memos, which come from DBE and provincial papers. A few things said on air or printed on the slides need correcting. They are flagged here rather than quietly fixed.

Said or shown	Correct version
Co-dominance described as producing an intermediate, and incomplete dominance as both alleles expressed equally	The other way round. Incomplete dominance gives an intermediate; in co-dominance both alleles are expressed equally.
"For a protein you need a group of about 20 amino acids"	There are 20 different kinds of amino acid. A protein is a chain of many amino acids, usually hundreds, joined by peptide bonds.
Translation slide: "mRNA leaves the nucleus through the nuclear pore to the ribose"	To the ribosome. Ribose is the sugar in RNA.
Nov 2021 dihybrid memo: "number of genotypes giving short fingers and a continuous hairline = 3"	Three squares of the table give that phenotype (FFhh, Ffhh, Ffhh), but they are only two different genotypes. The memo counted squares; read the question carefully and show which you counted.

Exam-style questions

Tabulate THREE observable differences between skull A (chimpanzee) and skull B (human). (7)

Skull A	Skull B
Rectangular / U-shaped palate ✓	Rounded / C-shaped / semi-circular / parabolic palate ✓
Large canines ✓	Small canines ✓
Foramen magnum in a more backward position ✓	Foramen magnum in a more forward position ✓
Large jaw ✓	Small jaw ✓
Prognathous / more protruding jaws ✓	Non-prognathous / less protruding jaws ✓

Table ✓ + any 3 × 2

Heila, Priya and Leo: identify the TWO biological children and explain. (4)

Heila ✓ and Leo ✓. All of the DNA bands from Heila and Leo ✓ match with the DNA bands of the mother and the father ✓. OR: none of the bands from Priya ✓ match with the DNA bands of the mother and father ✓.

Tabulate TWO differences between the features of Homo erectus and Homo sapiens using the passage. (5)

Homo erectus	Homo sapiens
Small brain ✓	Large brain ✓
Prominent brow ridges ✓	Reduced brow ridges ✓

Table ✓. Only use features the passage mentions.

What observation of the skull of Homo erectus would have led scientists to conclude that it was bipedal? (1)

The foramen magnum was in a (more) forward position ✓

One-page summary

• Evolution (54): Lamarck = use and disuse + inheritance of acquired characteristics; rejected (no evidence, DNA cannot change, genotype determines phenotype). Darwin = variation, environment changes, suited survive, reproduce, pass on the allele, higher proportion. Punctuated equilibrium = Eldredge and Gould 1972, speed of evolution, long equilibrium punctuated by rapid change. Speciation = population, barrier, split, no gene flow, different conditions, natural selection independently, genotypically and phenotypically different, cannot interbreed, different species.
• Human evolution: similarities (upright posture, binocular vision, cones, freely rotating arms, nails, opposable thumbs) and differences (foramen magnum forward, S-spine, short wide pelvis, larger cranium, rounded palate, small canines no diastema, flat face, no brow ridges). Out of Africa: Ardipithecus, Australopithecus, H. habilis in Africa only; oldest H. sapiens in Africa, younger elsewhere.
• Genetics (48): cross layout gives 3 free marks; co-dominance both capitals; dihybrid 9:3:3:1 and independent assortment; XY sons get Y from father; males show recessive X-linked traits; blood groups Iᴬ, Iᴮ, i; pedigree: read the key and the stem.
• DNA (27): deoxyribose vs ribose, double helix vs single, T vs U; replication (unwind, unzip, template, free nucleotides, two identical molecules); transcription in the nucleus, translation at the ribosome; mutation chain DNA to codon to anticodon to amino acid to protein; profile = black bars; paternity needs both parents.
• Meiosis (21): diploid, two divisions, four haploid; crossing over at chiasmata; anaphase I centromeres do not split; non-disjunction of pair 21 gives 24-chromosome gamete, 47-chromosome zygote, trisomy 21.

Source and further practice

Gauteng Department of Education and Sci-Bono Discovery Centre, Life Sciences Grade 12 Paper 2 revision broadcast, 17 September 2026, on the Phakama Research YouTube channel: youtube.com/watch?v=GQMA3Ly8TDM. Past-paper items on the slides: DBE November 2025 (ratites, blood groups), DBE November 2021 (dihybrid table), Free State November 2022 (haemophilia), KwaZulu-Natal Preparatory 2023 (Goltz pedigree). The presenters also recommend the Life Sciences learner Google Drive and "Dr G Life Sciences" on YouTube and TikTok.