Question

14 how do the four different nucleotides found in dna result in twenty different amino acids used to form proteins in the cell? a the four bases each specify one amino acid, and these then combine to form the other sixteen amino acids b the four nucleic acid bases combine in three letter sequences that each define and amino acid c the four nucleic acid bases are converted into trna molecules which can each attach to sixteen different amino acids d the four nucleic acid bases combine in two letter sequences that each define an amino acid

Explanation:

To solve this, we recall how DNA codes for amino acids. DNA nucleotides (A, T, C, G) form codons (three - letter sequences) that correspond to amino acids.

• Option A is wrong because a single base can't code for an amino acid, and amino acids don't combine to form others in this way.
• Option B is correct as codons are three - nucleotide (base) sequences, and each codon codes for one amino acid.
• Option C is wrong because tRNA has anticodons (complementary to codons) and each tRNA carries one specific amino acid, not sixteen.
• Option D is wrong because two - letter sequences would give only \(4^2 = 16\) combinations, but we have 20 amino acids, and the actual code uses three - letter codons (\(4^3=64\) combinations) to code for 20 amino acids.

Answer:

B. The four nucleic acid bases combine in three letter sequences that each define an amino acid