Would someone help me with the following...it's not A.Thnx!!
What would happen if the mRNA codon that coded for Cys was mutated in the third position from a U to an A?
A The codon would now code for Trp instead of Cys.
B A stop codon would be introduced prematurely.
C The amino acid Cys would still be coded.
B
A stop codon would be introduced prematurely.
To determine the possible outcome of the mRNA codon mutation, we need to refer to the mRNA codon chart, also known as the genetic code chart. This chart shows us which codons code for specific amino acids.
Step 1: Identify the original mRNA codon that codes for Cysteine (Cys).
The mRNA codon that codes for Cys is UGU.
Step 2: Determine the effect of the mutation by changing the third position of the codon from U to A.
By changing the third position from U to A, the mutated codon becomes UGA.
Step 3: Look up the codon UGA on the chart.
According to the genetic code chart, UGA normally codes for a stop codon (termination signal), indicating the end of protein synthesis.
Based on these steps, the correct answer is:
B. A stop codon would be introduced prematurely.
Note: Trp (tryptophan) is not coded by either UGU or UGA codons, so option A is incorrect. Option C is also incorrect because the original Cys codon (UGU) has been mutated.
By following these steps, you can understand how to apply the genetic code chart to determine the effect of a codon mutation.