[Campbell Biology P.476] Based on Figure 20.15 and the accompanying text, which statement be... | Practice Question

Based on Figure 20.15 and the accompanying text, which statement best describes how a SNP acts as a genetic marker for disease-associated alleles?

  • A: The SNP directly causes the disease by changing the protein sequence, as shown by the A-T to C-G change.
  • B: The SNP is located on a different chromosome than the disease-causing gene, allowing for independent assortment.
  • C: The SNP, such as the A-T pair in unaffected individuals or C-G pair in affected individuals, is closely linked to the disease-causing allele and is therefore almost always inherited with it.
  • D: The figure illustrates that a SNP acts as a marker because it is identical in both normal and disease-associated alleles.

Explanation

The text explains that a SNP 'is located very close to that SNP on that chromosome' which results in 'genetic linkage' meaning 'the SNP and gene are almost always inherited together, so the SNP acts as a genetic marker for the disease-causing allele'. Figure 20.15 visually confirms this by showing different SNP variants A-T vs C-G linked to normal vs. disease-associated alleles.