Question

A glycine residue is in position 210 of the tryptophan synthetase enzyme of wild-type \(E .\) coli. If the codon specifying glycine is GGA, how many single- base substitutions will result in an amino acid substitution at position \(210 ?\) What are they? How many will result if the wild-type codon is GGU?

Short answer

Answer: 5 single-base substitutions will result in an amino acid substitution at position 210 for the wild-type codon GGU.

Step-by-step solution

Understand the genetic code

The genetic code is the set of rules used by living cells to translate the information encoded within genetic material (DNA or RNA sequences) into proteins. Amino acids are represented by three-letter sequences called codons, in which each letter is a base. There are four different bases (A, U, C, and G) and \(4^3\) = 64 possible codons. Step 2: Determine the possible single-base substitutions

Determine the possible single-base substitutions

If the codon specifying glycine is GGA, there are three positions in the codon where a single-base substitution can occur: position 1 (G), position 2 (G), and position 3 (A). For each of these positions, we can substitute the original base with one of the other three bases (A, U, or C). Step 3: Analyze the effects of single-base substitutions on the amino acid produced

Analyze the effects of single-base substitutions on the amino acid produced

Now, we need to analyze how these possible substitutions will affect the amino acid that's produced. Using the genetic code table, we can determine the effects of single-base substitutions on the amino acid: 1. Substitution at position 1 (G): - GGA (Glycine) -> AGA (Arginine) - GGA (Glycine) -> UGA (Stop codon) - GGA (Glycine) -> CGA (Arginine) 2. Substitution at position 2 (G): - GGA (Glycine) -> GAA (Glutamic Acid) - GGA (Glycine) -> GUA (Valine) - GGA (Glycine) -> GCA (Alanine) 3. Substitution at position 3 (A): - GGA (Glycine) -> GGU (Glycine) - GGA (Glycine) -> GGC (Glycine) - GGA (Glycine) -> GGG (Glycine) Step 4: Count the number of amino acid substitutions

Count the number of amino acid substitutions

From Step 3, we can see that if the codon specifying glycine is GGA, 5 single-base substitutions will result in an amino acid substitution at position 210: GAA, AGA, UGA, GUA, and GCA. Step 5: Analyze the effects of single-base substitutions on the wild-type codon GGU

Analyze the effects of single-base substitutions on the wild-type codon GGU

Repeat steps 2 and 3 for the wild-type codon GGU: 1. Substitution at position 1 (G): - GGU (Glycine) -> AGU (Serine) - GGU (Glycine) -> UGU (Cysteine) - GGU (Glycine) -> CGU (Arginine) 2. Substitution at position 2 (G): - GGU (Glycine) -> GAU (Aspartic Acid) - GGU (Glycine) -> GUU (Valine) - GGU (Glycine) -> GCU (Alanine) 3. Substitution at position 3 (U): - GGU (Glycine) -> GGA (Glycine) - GGU (Glycine) -> GGC (Glycine) - GGU (Glycine) -> GGG (Glycine) Step 6: Count the number of amino acid substitutions for the wild-type codon GGU

Count the number of amino acid substitutions for the wild-type codon GGU

From Step 5, we can see that if the wild-type codon is GGU, 5 single-base substitutions will result in an amino acid substitution at position 210: AGU, UGU, CGU, GAU, GUU, and GCU.