Question

the genetic code provides instructions for making proteins. which statement best explains how the genetic code is universal?

a. dna sequences are unique for each species.

b. the shape of a dna molecule is the same in different species.

c. a dna sequence codes for the same proteins in different species.

d. the nucleotide ratios in the dna molecule are different between species.

Explanation:

To determine the best explanation for the universality of the genetic code, we analyze each option:

• Option A: DNA sequences being unique for each species relates to genetic diversity, not universality. Eliminate A.
• Option B: The shape of DNA (double helix) being the same across species is about structure, not the code's universality (which is about coding for proteins). Eliminate B.
• Option C: The genetic code is universal because a particular DNA sequence (codon) codes for the same amino acid (and thus the same protein) in different species. This matches the definition of a universal genetic code.
• Option D: Different nucleotide ratios between species do not explain the universality of the code (which is about consistent protein coding). Eliminate D.

Answer:

C. A DNA sequence codes for the same proteins in different species.