Loading subjects
Gene Expression · Part 3 of 3
9 exam-style questions with model answers, plus 12 quick multi-choice questions — every question on this part of the standard, grouped by the 3 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Define a metabolic pathway, and state the relationship between genes and the enzymes in it.
Explain how a mutation in a single gene can change an organism's phenotype, using a metabolic pathway in your answer.
A metabolic pathway converts P to Q to R. Two individuals lack pigment R. One accumulates large amounts of P; the other accumulates large amounts of Q. Both have the same phenotype. Discuss what this reveals, and evaluate whether phenotype alone is sufficient to identify a genetic condition.
Define a mutation and a mutagen, and give two examples of mutagens.
Explain why a deletion of one base is usually far more damaging to a protein than a substitution of one base.
A person's skin cells accumulate mutations from UV exposure over many years. Discuss the possible consequences, and explain why these mutations cannot be passed to their children while a change in skin colour from tanning also cannot.
Give one example of an environmental factor changing an organism's phenotype, and state what happens to the genotype.
A Himalayan rabbit has white body fur and dark ears, nose, tail and feet. Explain how this happens, given that every cell in the rabbit has the same genotype.
Identical twins are separated at birth and raised in different countries with very different diets and climates. As adults they differ in height, skin tone and muscle mass. Discuss what this reveals about the relationship between genotype, environment and phenotype, and evaluate what conclusions can and cannot be drawn.