U3 AOS 1 - Genetics
What are the three components of a nucleotide?
A phosphate group, a five-carbon (pentose) sugar and a nitrogenous base.
What is an enzyme's active site?
The region where the substrate binds. Its shape and chemistry are complementary to the substrate.
What is phagocytosis?
A cell engulfing and digesting a pathogen or debris.
What is the original source of all new alleles in a gene pool?
Mutations
What is the difference between an independent and a dependent variable?
The independent variable is changed by the investigator. The dependent variable is measured.
Which enzyme joins DNA fragments by forming phosphodiester bonds?
DNA Ligase
How does a competitive inhibitor work?
It has a similar shape to the substrate and binds the active site, so the substrate can’t bind.
Give an example of natural active OR natural passive immunity.
Natural active: recovering from an infection.
Natural passive: antibodies passed across the placenta or in breast milk.
What are homologous structures? Give an example.
Structures with the same basic plan, inherited from a common ancestor, but with different functions. Example: the pentadactyl limb.
What is the purpose of a control group?
It gives a baseline for comparison, showing that any change is due to the independent variable.
Name the three stages of PCR and their approximate temperatures.
Denaturation (~95°C), annealing of primers (~50–65°C), extension by Taq polymerase (~72°C).
Where does glycolysis occur, and what does it produce?
In the cytosol. It produces 2 pyruvate, a net 2 ATP and 2 NADH per glucose.
What is the role of mast cells in inflammation?
They release histamine, which causes vasodilation and leaky capillaries. This brings redness, heat, swelling and more immune cells to the site.
What is the difference between the bottleneck effect and the founder effect?
In a bottleneck, a population is sharply reduced by an event such as a disaster. In the founder effect, a small group leaves to start a new population. Both are forms of genetic drift and reduce genetic diversity.
What is the difference between accuracy and precision?
Accuracy is how close a result is to the true value. Precision is how close repeated results are to each other.
In the trp operon, what happens when tryptophan levels are high?
Tryptophan binds the repressor and activates it. The repressor then binds the operator and blocks RNA polymerase, so the structural genes aren’t transcribed.
What does the enzyme Rubisco do, and what is its main limitation?
Rubisco fixes CO₂ onto RuBP in the Calvin cycle. It can also bind O₂, which causes photorespiration and wastes energy, especially in hot, dry conditions.
What is the difference between MHC I and MHC II markers?
MHC I is on all nucleated cells and presents antigen to cytotoxic T cells. MHC II is only on antigen-presenting cells and presents antigen to helper T cells.
Give a skeletal feature that indicate bipedalism in hominins.
Any three of: a central foramen magnum, an S-shaped spine, a bowl-shaped pelvis, an angled femur, an arched foot with an aligned big toe.
What is the difference between random and systematic errors, and how is each reduced?
Random errors vary unpredictably and are reduced with repeats, averaging and larger samples. Systematic errors shift every result the same way and are reduced by calibrating equipment or improving the method.
Trace the path of a protein made for export, from ribosome to outside the cell.
Ribosome on rough ER → protein enters the RER and folds → transport vesicle → Golgi modifies and packages it → secretory vesicle → exocytosis.
How do C4 and CAM plants reduce photorespiration?
C4 plants separate the steps in space: CO₂ is fixed in mesophyll cells and shuttled to bundle-sheath cells. CAM plants separate them in time: stomata open at night to store CO₂ as acids, which release it during the day.
What are monoclonal antibodies, and how can they be used to treat cancer?
They are identical antibodies made by a hybridoma (a B cell fused with a myeloma cell). They can flag tumour cells for destruction, deliver attached drugs, or block checkpoint proteins such as PD-1.
Explain allopatric speciation using a named example.
Example: Galápagos finches. Populations on separate islands faced different selection pressures, built up differences in beak shape, and became reproductively isolated species.
Name the an approach to bioethics in the VCE study design and explain one.
Consequences-based, duty/rule-based and virtues-based. For example, the consequences-based approach judges an action by its outcomes.