Molecular genetics
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Which statement gives the correct relationship?
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A gene is a section of DNA carried on a chromosome.
Keep the molecule, a particular sequence and the organised chromosome structure distinct.
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Which bases sit directly opposite T G A C in the displayed order?
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A C T G
Apply T-A, G-C, A-T and C-G at the four corresponding positions.
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A DNA sample contains 30% adenine. What percentage of its bases is cytosine?
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20%
A pairs with T, so T = 30% and A + T = 60%. That leaves 40% for C and G, so C = 20%.
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Which chain best explains how a gene can affect enzyme activity?
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DNA base sequence specifies amino acid sequence, which affects protein shape and function.
This connects inherited information to the structure and activity of the protein product.
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A gene has 900 bases in the coding sequence, read in groups of three. How many amino acids can it code for at most?
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300
Three bases code for one amino acid, so 900 / 3 = 300.
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Write a short answer, then compare it with a sample and check for missing ideas.