Fundamentals
The core facts every aspirant should own — each a titled nugget with a real-world story, the concept in plain words, and a memory trick. Works even when the internet doesn't.
300 fundamentals
“Whales still have tiny hip bones — fossils of legs from land-walking ancestors.”
Natural selection favours the best-adapted to the environment, which is not the same as the physically strongest.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
A frequent error is thinking all immunity is present from birth. In reality, innate immunity is the non-specific defence we're born with; acquired immunity is specific and develops after exposure.
Memory trick: innate = general and immediate; acquired = specific and remembers pathogens.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
A frequent error is calling a vaccine passive immunity. In reality, active immunity is when the body makes its own antibodies; passive immunity is receiving ready-made ones.
Memory trick: a vaccine triggers your OWN antibodies → active; antivenom is ready-made → passive.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
A frequent error is thinking antibodies and antigens are the same thing. In reality, protein molecules made by B-lymphocytes that bind and neutralise specific antigens.
Memory trick: antigen triggers; antibody attacks.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
Medicines that kill or stop bacteria — they do not work against viruses.
Memory trick: antibiotics target bacteria only; misuse breeds resistance.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
A frequent error is taking antibiotics for a viral cold or flu. In reality, medicines that kill or stop bacteria — they do not work against viruses.
Memory trick: antibiotics target bacteria only; misuse breeds resistance.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
Innate immunity is fast and non-specific (skin, phagocytes); acquired immunity is slower, specific, and has memory (antibodies).
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
Active immunity is made by your own body (vaccine, infection) and lasts long; passive immunity is borrowed antibodies (mother's milk, antivenom) and is short-lived.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
An antigen is a foreign molecule that triggers a response; an antibody is the protein the body makes to bind and neutralise it.
“A vaccine is a 'wanted poster' that trains your immune system before the real criminal shows up.”
Antibiotics act only on bacteria; they are useless against viruses like the common cold, and overuse causes resistance.
“You began as a single cell smaller than a full stop on this page.”
The formation of gametes — spermatogenesis makes four sperm per cell, oogenesis makes one ovum plus polar bodies.
Memory trick: oogenesis → 1 ovum (the rest are polar bodies); spermatogenesis → 4 sperm.
“You began as a single cell smaller than a full stop on this page.”
A frequent error is thinking oogenesis produces four functional eggs like spermatogenesis makes four sperm. In reality, the formation of gametes — spermatogenesis makes four sperm per cell, oogenesis makes one ovum plus polar bodies.
Memory trick: oogenesis → 1 ovum (the rest are polar bodies); spermatogenesis → 4 sperm.
“You began as a single cell smaller than a full stop on this page.”
A frequent error is thinking ovulation happens at the start of the cycle. In reality, a ~28-day hormonal cycle in which ovulation occurs around day 14, driven by FSH, LH, estrogen and progesterone.
Memory trick: ovulation is mid-cycle (~day 14), roughly halfway.
“You began as a single cell smaller than a full stop on this page.”
The fusion of sperm and ovum, which happens in the ampulla of the fallopian tube, not the uterus.
Memory trick: fertilisation is in the oviduct; the embryo then implants in the uterus.
“You began as a single cell smaller than a full stop on this page.”
A frequent error is thinking fertilisation occurs in the uterus. In reality, the fusion of sperm and ovum, which happens in the ampulla of the fallopian tube, not the uterus.
Memory trick: fertilisation is in the oviduct; the embryo then implants in the uterus.
“You began as a single cell smaller than a full stop on this page.”
A frequent error is thinking maternal and foetal blood mix directly. In reality, the structure connecting the embryo to the mother's uterus for nutrient, gas and waste exchange, and it also secretes hormones.
Memory trick: the placenta exchanges materials by diffusion — the two bloodstreams stay separate.
“You began as a single cell smaller than a full stop on this page.”
The menstrual phase is the shedding of the uterine lining at the cycle's start; ovulation is the release of the egg around mid-cycle.
“You began as a single cell smaller than a full stop on this page.”
Fertilisation occurs in the ampulla of the fallopian tube; the resulting embryo then travels to and implants in the uterus.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
A frequent error is thinking any gene can be expressed without a proper vector and host. In reality, inserting a desired gene into a vector and then a host cell to mass-produce a useful product.
Memory trick: gene + vector (plasmid) + host cell = the recombinant DNA workflow.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
A frequent error is thinking restriction enzymes cut DNA at random points. In reality, molecular scissors that cut DNA only at specific palindromic recognition sequences.
Memory trick: each restriction enzyme recognises one specific sequence and cuts only there.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
A technique that makes millions of copies of a DNA segment using primers and heat-stable Taq polymerase.
Memory trick: PCR = photocopier for DNA; electrophoresis = sorting DNA by size.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
A frequent error is confusing PCR (which amplifies DNA) with gel electrophoresis (which separates it). In reality, a technique that makes millions of copies of a DNA segment using primers and heat-stable Taq polymerase.
Memory trick: PCR = photocopier for DNA; electrophoresis = sorting DNA by size.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
Genetic engineering gives us human insulin, Bt crops, and gene therapy.
Memory trick: recombinant human insulin is identical to the body's own — that's why it works so well.
“The insulin that keeps millions alive is now brewed by bacteria we reprogrammed.”
A frequent error is thinking genetically engineered insulin differs from human insulin. In reality, genetic engineering gives us human insulin, Bt crops, and gene therapy.
Memory trick: recombinant human insulin is identical to the body's own — that's why it works so well.