Distinguish copies, cells and function
Review mitosis, independent inheritance and enzymes.
The idea
Chromosome number and DNA amount are different measures. Independent genetic events combine by multiplication; enzymes change the reaction pathway without changing equilibrium.
A method to try
- State what is counted: chromosomes, chromatids or cells.
- Calculate each independent probability separately.
Follow the reasoning.
In a simple monohybrid cross Tt × tt with complete dominance, what fraction of offspring is expected to have the recessive phenotype?
- The Tt parent contributes T or t with equal probability. The tt parent contributes only t.
- The resulting possibilities are Tt and tt, each with probability one half. Only tt has the recessive phenotype under the stated complete-dominance model.
- These are probabilities for each offspring, not a guarantee that every pair of offspring contains exactly one of each phenotype. Keep expected proportions separate from the outcome of a small actual sample.
Think it through first.
Does an enzyme change the equilibrium constant of the reaction it catalyses?
Show the explanation
No.
It lowers the activation barrier for the reaction pathway and speeds approach to equilibrium without changing the equilibrium position.
Make it your own
After reading, explain the method in your own words and identify the condition that makes it valid. Then try the linked starter practice without referring back to the worked example. Review the reasoning behind an error before repeating the same item; remembering an answer is different from being able to solve a new problem.
This lesson is one part of a short starter pathway. It does not cover the full exam syllabus or establish a predicted score.
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- University of Pavia: IMAT admission test (opens in a new tab)Checked 2026-09-20
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