To reconstruct the evolutionary relationships among several newly discovered species of desert rodents, taxonomists choose to compare the nucleotide base sequences of a specific gene rather than the amino acid sequences of its encoded protein.
Which statement correctly explains why comparing DNA base sequences provides a more accurate representation of evolutionary divergence than comparing amino acid sequences?
Splicing removes exons from pre-mRNA, meaning that the resulting amino acid sequence lacks key variable regions that are preserved in the genomic DNA sequence.
The genetic code is degenerate, meaning some different codons code for the same amino acid; thus, silent mutations can accumulate in DNA without altering the amino acid sequence.
Natural selection acts directly on the DNA sequence rather than the protein phenotype, causing DNA mutations to accumulate at a more stable, neutral rate.
Non-coding introns undergo high levels of directional selection, making their base sequences highly conserved compared to the rapidly mutating amino acid sequences of exons.
122 exam-style questions on OCR GCSE Biology 5.2 Natural selection and evolution, covering 5.2.1 Genetic variation within a population, 5.2.2 Developments in classification systems, 5.2.3 How evolution occurs through natural selection, 5.2.4 Evolution as change over time, 5.2.5 Evidence for evolution, and 5.2.6 Darwin and Wallace. Each one has a worked solution and a mark scheme showing where the marks go.