Life Sciences Grade 12 Examination Guidelines – Key Vocabulary

Vocabulary flashcards summarising essential terms and definitions from the Grade 12 Life Sciences Examination Guidelines, covering assessment framework, molecular genetics, reproduction, genetics, nervous and endocrine systems, plant responses, and evolution.

CAPS (Curriculum and Assessment Policy Statement)

South African national curriculum policy that prescribes content, teaching and assessment for each subject.

NSC (National Senior Certificate)

South Africa’s school-leaving qualification obtained after Grade 12.

Specific Aim 1 (Life Sciences)

Knowing the subject content.

Specific Aim 2 (Life Sciences)

Doing science – practical work and investigations.

Specific Aim 3 (Life Sciences)

Understanding applications of Life Sciences, history of discoveries and links to indigenous knowledge.

Cognitive Level A – Knowledge

Lowest cognitive level; recall of facts (40 % weighting).

Cognitive Level B – Comprehension

Understanding and interpreting concepts (25 % weighting).

Cognitive Level C – Application

Using knowledge in new situations (20 % weighting).

Cognitive Level D – Analysis / Synthesis / Evaluation

Higher-order thinking skills (15 % weighting).

Degree of Difficulty: Easy

Questions 30 % of paper; answerable by an average learner.

Degree of Difficulty: Moderate

Questions 40 % of paper; moderately challenging.

Degree of Difficulty: Difficult

Questions 25 % of paper; difficult for average learner.

Degree of Difficulty: Very Difficult

Questions 5 % of paper; discriminate top achievers.

DNA (Deoxyribonucleic Acid)

Double-helical nucleic acid that stores hereditary information in cells.

RNA (Ribonucleic Acid)

Single-stranded nucleic acid involved in protein synthesis.

Nucleotide

Building block of nucleic acids; consists of a phosphate, a sugar and a nitrogenous base.

Nitrogenous Bases (DNA)

Adenine, Thymine, Cytosine, Guanine.

Base-Pair Rule (DNA)

A pairs with T, G pairs with C via hydrogen bonds.

Nitrogenous Bases (RNA)

Adenine, Uracil, Cytosine, Guanine.

Watson & Crick

Scientists who proposed the double-helix model of DNA in 1953.

Franklin & Wilkins

Researchers whose X-ray diffraction images aided discovery of DNA structure.

DNA Replication

Semi-conservative process producing two identical DNA molecules before cell division.

DNA Profiling

Technique that analyses non-coding DNA regions to identify individuals.

mRNA (Messenger RNA)

RNA copy of a gene that carries the code from nucleus to ribosome.

tRNA (Transfer RNA)

RNA molecule that transports specific amino acids to ribosomes during translation.

Transcription

Stage of protein synthesis where DNA template is copied into mRNA.

Translation

Assembly of amino acids into a polypeptide at the ribosome using mRNA code.

Codon

Three-base sequence on mRNA that codes for an amino acid.

Anticodon

Three-base sequence on tRNA complementary to an mRNA codon.

Peptide Bond

Chemical bond linking amino acids in a protein.

Meiosis

Cell division producing four genetically different haploid gametes.

Haploid (n)

Cell with one set of chromosomes (e.g., gametes).

Diploid (2n)

Cell with two sets of chromosomes (e.g., somatic cells).

Crossing Over

Exchange of genetic material between homologous chromosomes during Prophase I.

Random Assortment

Independent orientation of homologous pairs at Metaphase I producing genetic variety.

Non-disjunction

Failure of chromosomes to separate during meiosis, leading to aneuploidy.

Down Syndrome

Genetic disorder caused by trisomy 21 resulting from non-disjunction.

Mitosis

Nuclear division producing two identical diploid daughter cells.

Ovipary

Reproductive strategy where eggs are laid externally and develop outside the mother.

Ovovivipary

Internal development of eggs that hatch inside the mother; no placental nourishment.

Vivipary

Development of offspring inside the mother with nutritional support via placenta.

External Fertilisation

Gametes fuse outside the bodies of the parents (e.g., fish).

Internal Fertilisation

Gametes fuse inside the female reproductive tract (e.g., mammals).

Amniotic Egg

Egg with protective membranes and shell enabling terrestrial development in reptiles/birds.

Precocial Development

Young are relatively mature and mobile at birth/hatching.

Altricial Development

Young are helpless and require extensive parental care post-birth.

Testis

Male gonad producing sperm and testosterone.

Epididymis

Coiled tube where sperm mature and are stored.

Vas Deferens

Duct transporting sperm from epididymis to urethra.

Seminal Vesicle

Gland secreting fructose-rich fluid contributing to semen.

Prostate Gland

Gland adding alkaline fluid to semen to enhance sperm motility.

Cowper’s (Bulbourethral) Gland

Secretes mucus-rich fluid that lubricates urethra before ejaculation.

Ovary

Female gonad producing ova, oestrogen and progesterone.

Fallopian Tube (Oviduct)

Duct where fertilisation usually occurs and zygote is conveyed to uterus.

Uterus (Womb)

Muscular organ where embryo implants and foetus develops.

Endometrium

Vascular lining of uterus that thickens and sheds during menstrual cycle.

Cervix

Lower narrow portion of uterus opening into vagina.

Graafian Follicle

Mature ovarian follicle containing the secondary oocyte prior to ovulation.

Corpus Luteum

Yellow body in ovary secreting progesterone after ovulation.

FSH (Follicle-Stimulating Hormone)

Pituitary hormone stimulating follicle growth and sperm production.

LH (Luteinising Hormone)

Pituitary hormone triggering ovulation and testosterone secretion.

Oestrogen

Ovarian hormone promoting female secondary sex traits and endometrium thickening.

Progesterone

Ovarian hormone maintaining endometrium and pregnancy.

Testosterone

Male hormone responsible for male secondary sex characteristics and spermatogenesis.

Spermatogenesis

Meiotic formation of haploid sperm in seminiferous tubules.

Oogenesis

Meiotic formation of haploid ova in ovaries.

Menstruation

Shedding of endometrial lining when fertilisation does not occur.

Ovulation

Release of secondary oocyte from ovary into Fallopian tube.

Fertilisation

Fusion of male and female gametes forming a diploid zygote.

Zygote

Fertilised egg cell prior to cleavage divisions.

Morula

Solid ball of cells resulting from early mitotic divisions of zygote.

Blastocyst

Hollow ball of cells with an inner cell mass that implants in uterus.

Implantation

Attachment of blastocyst to endometrium.

Placenta

Organ facilitating exchange of nutrients, gases and wastes between mother and foetus.

Amnion

Membrane enclosing amniotic fluid around embryo for protection.

Umbilical Cord

Connects foetus to placenta; contains one vein (oxygenated blood) and two arteries (deoxygenated).

Gene

Segment of DNA coding for a specific protein/trait.

Allele

Alternative form of a gene found at the same locus.

Dominant Allele

Allele expressed in phenotype even when heterozygous.

Recessive Allele

Allele expressed only when homozygous.

Genotype

Genetic constitution of an organism for a trait.

Phenotype

Observable characteristics resulting from genotype and environment.

Homozygous

Having two identical alleles for a gene.

Heterozygous

Having two different alleles for a gene.

Complete Dominance

One allele completely masks the other in heterozygote.

Incomplete Dominance

Neither allele is dominant; heterozygote shows intermediate phenotype.

Co-dominance

Both alleles fully expressed in heterozygote (e.g., AB blood group).

Multiple Alleles

More than two alternative alleles for a gene (e.g., ABO blood group).

Sex Chromosomes (Gonosomes)

Chromosome pair determining sex (XX female, XY male in humans).

Autosomes

Non-sex chromosomes (22 pairs in humans).

Sex-linked Gene

Gene located on a sex chromosome, often X-linked.

Haemophilia

X-linked recessive disorder causing impaired blood clotting.

Colour Blindness

X-linked recessive inability to distinguish certain colours.

Pedigree

Diagram showing inheritance of traits through generations.

Mutation

Permanent change in DNA sequence; source of new alleles.

Gene Mutation

Alteration of nucleotide sequence in a single gene.

Chromosomal Mutation

Change in chromosome number or structure (e.g., trisomy 21).

Biotechnology

Use of living organisms or processes to meet human needs.

Genetic Engineering

Direct manipulation of genes, including GMOs, cloning, stem-cell research.

GMO (Genetically Modified Organism)

Organism with inserted foreign DNA to express desired traits.