Question

REFLECT AND APPLY Why is it advantageous to have a mechanism to override the effect of stop codons in protein synthesis?

Short answer

Overriding stop codons ensures full-length functional proteins are produced, enhancing cellular resilience and adaptability.

Step-by-step solution

Understanding Stop Codons

Stop codons are sequences of nucleotides in mRNA that signal the end of protein synthesis. They prompt the ribosome to release the newly formed polypeptide chain.

Consequence of Premature Stop Codons

Premature stop codons can lead to truncated proteins that are often nonfunctional or harmful. An override mechanism can help ensure that full-length, functional proteins are produced.

Mechanism of Overriding Stop Codons

Some cells have mechanisms, often involving suppressor tRNAs or specific proteins, that can recognize and bypass premature stop codons. This allows translation to continue until a natural stop codon is reached.

Advantage of Overriding Mechanisms

Having mechanisms to override stop codons allows cells to produce necessary proteins even in the presence of genetic mutations. This enhances adaptability and resilience.

Application of Overriding Mechanisms

Such mechanisms are particularly important in situations where genetic mutations are common, such as in rapidly evolving organisms or those exposed to high levels of mutagens.

Key concepts

Stop Codons

Stop codons are special sequences of nucleotides in mRNA that mark the end of protein synthesis. They are like the period at the end of a sentence, signaling the ribosome to release the newly formed polypeptide chain.
There are three stop codons in the genetic code: UAG, UAA, and UGA. Each of these tells the ribosome that the protein is complete.
Without stop codons, the ribosome would keep adding amino acids, creating a protein that's too long and often nonfunctional.

Protein Synthesis

Protein synthesis is the process by which cells create new proteins. It involves two main steps: transcription and translation.
During transcription, DNA is copied into mRNA, which carries the genetic information to the ribosome.
In translation, the ribosome reads the mRNA sequence and assembles the corresponding amino acids into a polypeptide chain.
Stop codons play a crucial role in this process by signaling when the protein is complete, ensuring that each protein is made accurately and to the correct length.

Suppressor tRNAs

Suppressor tRNAs are special types of tRNAs that can recognize and override stop codons. Normally, tRNAs match mRNA codons with the appropriate amino acid. However, suppressor tRNAs can bind to stop codons and insert an amino acid instead of terminating translation.
This ability to bypass stop codons is beneficial when dealing with premature stop codons, which can result from genetic mutations. Suppressor tRNAs allow the ribosome to ignore these premature signals and continue making a full-length, functional protein.
It's like having an emergency override button that ensures the protein synthesis process isn't interrupted prematurely.

Genetic Mutations

Genetic mutations are changes in the DNA sequence that can affect protein synthesis. These mutations can happen naturally or be caused by external factors like radiation or chemicals.
One type of mutation is a point mutation, where a single nucleotide change can introduce a premature stop codon. This premature stop codon can result in a truncated, often nonfunctional protein.
Mechanisms to override these premature stop codons, such as suppressor tRNAs, provide a way for cells to produce the necessary proteins even in the presence of such mutations.
This ability is crucial for organisms, especially in environments where genetic mutations occur frequently, enhancing their adaptability and survival.