A DNA variant lies outside the sequence coding for an enzyme. Researchers compare equal numbers of cells with and without the variant.
Cells with the variant contain one-quarter as many enzyme molecules. Purified samples containing equal numbers of enzyme molecules from the two cell groups have the same activity. The amino acid sequences are also identical.
Which explanation best accounts for all three observations?
The variant changes carrier specificity, reducing the number of amino acids brought to each protein.
The variant changes protein folding, reducing the proportion of enzymes able to bind their substrate.
The variant reduces gene expression, reducing enzyme production without changing the protein's amino acid sequence.
The variant changes triplet order, reducing enzyme production by shortening the protein's amino acid sequence.
76 exam-style questions on AQA GCSE Biology 6.1 Reproduction, covering 6.1.1 Sexual and asexual reproduction, 6.1.2 Meiosis, 6.1.3 Advantages and disadvantages of sexual and asexual reproduction, 6.1.4 DNA and the genome, 6.1.5 DNA structure, 6.1.6 Genetic inheritance, 6.1.7 Inherited disorders, and 6.1.8 Sex determination. Each one has a worked solution and a mark scheme showing where the marks go.