Multiple Choice
Which of the following mutations, occurring just after the start codon in the mRNA is likely to have the most serious effects on the polypeptide product?
15. Gene Expression
Mutations
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A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout an organism's chromosomes. This will probably cause __________.
A
the DNA to break up into thousands of short segments
B
incorrect pairing between mRNA codons and amino acids
C
no bad effects, as long as the stop codons are not also inserted into tRNA
D
manufactured proteins to be short and defective
Verified step by step guidance1
Understand the role of stop codons in protein synthesis. Stop codons are sequences in mRNA that signal the termination of translation, leading to the release of the newly synthesized polypeptide chain.
Recognize that the insertion of stop codons into DNA can lead to premature termination of mRNA translation. This means that the ribosome will stop translating the mRNA into a protein earlier than intended.
Consider the impact of premature stop codons on protein synthesis. If a stop codon is inserted within a coding sequence, the resulting mRNA will produce a truncated protein, which is often nonfunctional or defective.
Evaluate the consequences of having multiple stop codons inserted randomly throughout the genome. This would likely result in many proteins being shortened and unable to perform their normal functions, leading to cellular dysfunction.
Conclude that the presence of these stop codons will cause manufactured proteins to be short and defective, as the translation process is interrupted prematurely, preventing the full-length protein from being synthesized.
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