Module 5
Explain the role of mRNA in protein synthesis.
mRNA carries the genetic code from DNA in the nucleus to ribosomes for translation into proteins.
What type of mutation changes one base but does not affect the amino acid produced?
Silent mutation
Name one pathogen that causes disease in plants.
P Cinnamomi, Fusarium fungi (Panama disease), Tobacco mosaic virus, Rust fungi
What part of the brain controls body temperature regulation?
Hypothalamus
Earth Science: Explain how convection currents in the mantle drive plate tectonics.
Heat from the core causes mantle material to rise, cool, and sink, creating convection currents that move tectonic plates on Earth’s surface.
Why is DNA replication described as semi-conservative?
Each new DNA molecule has one original strand and one newly synthesised strand.
Identify at least 3 ecological risks of releasing genetically modified organisms into the environment.
Risks include gene flow to wild populations, reduced biodiversity, disruption of ecosystems, and the evolution of resistant pests or weeds.
Which of Koch’s postulates requires isolating a pure culture of the pathogen?
The second postulate.
Explain how a mutation in a single gene can lead to a non-infectious disease, giving an example.
A single gene mutation can produce a faulty protein that disrupts normal function, e.g., a mutation in CFTR causes cystic fibrosis, affecting chloride transport and lung function.
Chemistry: Explain why catalysts speed up reactions without being consumed.
Catalysts lower the activation energy by providing an alternative reaction pathway, but they are regenerated at the end of the reaction and not used up.
A pedigree shows a rare trait affecting only males. Carrier mothers pass the trait to half their sons but not their daughters. What type of inheritance is this, and why?
X-linked recessive; males inherit only one X, so a single copy of the allele results in expression, while daughters need two copies.
Outline how bacterial plasmids are used as vectors in recombinant DNA technology. Be detailed.
Plasmids carry inserted genes into host cells, replicate independently, and often contain selectable markers (e.g., antibiotic resistance) for identifying transformed cells.
Explain at least one way plant cells defend themselves against pathogens.
Thickening cell walls with lignin, producing antimicrobial chemicals, programmed cell death (hypersensitive response).
Explain the difference between myopia and hyperopia.
Myopia = short-sightedness, light focuses in front of the retina; Hyperopia = long-sightedness, light focuses behind the retina.
Biology: What is the chemical formula for glucose?
C₆H₁₂O₆
Explain how non-disjunction during meiosis leads to conditions such as Down syndrome.
Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate, producing gametes with abnormal chromosome numbers
Describe the process of somatic cell nuclear transfer
Remove nucleus from egg cell → Insert nucleus from a somatic cell → Stimulate cell to divide using electric shock→ Implant into surrogate to develop.
Explain how prions cause disease.
Prions are misfolded proteins that trigger normal proteins to misfold, leading to protein build-up in the brain and causing neurodegeneration.
Explain how dialysis machines replicate kidney function.
Dialysis machines use a semi-permeable membrane and dialysate to remove wastes and excess water from blood. Wastes diffuse into the dialysate, while important substances remain in the blood, mimicking kidney function.
Physics: Explain why a heavier object and a lighter object fall at the same rate in a vacuum.
Without air resistance, acceleration due to gravity is constant for all masses (~9.8 m/s²), so objects fall at the same rate regardless of weight.
Explain how differences in coding and non-coding DNA regions affect an organism’s phenotype. (Perfect answers only)
Coding DNA determines amino acid sequences in proteins; non-coding DNA regulates gene expression (e.g., turning genes on/off), both influencing phenotype.
Outline an example of how recombinant DNA technology can be used to produce human proteins.
Human gene is inserted into bacterial plasmid → plasmid introduced into bacteria → bacteria express the human protein (e.g., insulin manufacturing).
How does vaccination protect individuals from disease?
Vaccination introduces a harmless form of an antigen (from a killed, weakened, or inactivated pathogen, or part of it) into the body. This stimulates the adaptive immune system to produce a primary immune response, including antibodies and memory B and T cells. If the individual is later exposed to the real pathogen, these memory cells enable a faster and stronger secondary immune response. This prevents illness by destroying the pathogen before it can cause disease.
Explain how negative feedback regulates blood glucose.
When blood glucose rises after a meal, the pancreas releases insulin, which helps cells absorb glucose and store it as glycogen, lowering blood glucose back to normal. When blood glucose falls, the pancreas releases glucagon, which signals the liver to break down glycogen into glucose, raising blood glucose back to normal. These opposing responses form a negative feedback loop that maintains stable blood glucose levels.
Biology: Compare hypertonic, isotonic, and hypotonic solutions and their effect on cells.
Hypertonic: Higher solute concentration outside → water leaves the cell → cell shrinks.
Isotonic: Equal solute concentration → no net water movement → cell size remains the same.
Hypotonic: Lower solute concentration outside → water enters the cell → cell swells and may burst.