Question

REFLECT AND APPLY Is it reasonable that codons for the same amino acid have one or two nucleotides in common? Why or why not?

Short answer

Yes, it is reasonable because shared nucleotides reduce errors in protein synthesis.

Step-by-step solution

Understand Codons and Amino Acids

Codons are sequences of three nucleotides in mRNA that correspond to a specific amino acid or a stop signal during protein synthesis. Each amino acid can be encoded by multiple codons, forming a codon family.

Analyze Nucleotide Commonality

Having one or two nucleotides in common within codons for the same amino acid can decrease the likelihood of errors during protein synthesis. If there’s a mutation in one nucleotide, the resulting codon might still encode the same amino acid, thus reducing potential errors in the protein produced.

Provide an Example

For instance, the amino acid leucine is encoded by the codons CUA, CUG, CUU, and CUC. Notice that they all share the 'CU' sequence, indicating that they have two nucleotides in common.

Draw a Conclusion

It is reasonable for codons for the same amino acid to have one or two nucleotides in common because it enhances the robustness of genetic coding, allowing minor mutations to occur without altering the resulting protein.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins. There are 20 different amino acids, each of which has a unique side chain that determines its properties and function. These amino acids link together in various sequences to form proteins, which are essential for the structure, function, and regulation of the body’s tissues and organs.

Amino acids play a crucial role in protein synthesis as they are the end products translated from mRNA sequences. During this process, the sequence of nucleotides in the mRNA determines the sequence of amino acids in the protein, ultimately influencing the protein's structure and function.

• Essential amino acids: These cannot be synthesized by the human body and must be obtained from the diet.
• Non-essential amino acids: These can be synthesized by the body.
• Polar, non-polar, acidic, and basic amino acids: These classifications are based on the properties of their side chains.

Learning the role of amino acids in the larger context of genetics helps grasp how proteins are formed and why codon redundancy, where multiple codons can code for a single amino acid, is beneficial.

Genetic Code

The genetic code is a set of instructions within the DNA that specifies how to synthesize proteins. It consists of sequences of three nucleotide bases called codons, each of which corresponds to a specific amino acid or a stop signal during protein synthesis.

The genetic code is universal across almost all organisms, meaning the same codons specify the same amino acids in different species. This universality is crucial for the precision of genetic information transfer across generations.

• Redundancy: This means that multiple codons can encode the same amino acid. For example, both GGA and GGG encode the amino acid glycine. This reduces the risk of mutations causing harmful effects.
• Unambiguous: Each codon only encodes one specific amino acid, ensuring clarity in protein synthesis.
• Non-overlapping: Codons are read one at a time, without overlapping, from a fixed starting point in the mRNA sequence. This ensures accurate reading frames for protein synthesis.

Understanding how the genetic code works is fundamental to comprehending how genetic information is translated into proteins and why processes such as codon redundancy are beneficial for maintaining genetic fidelity.

Protein Synthesis

Protein synthesis is the process by which cells generate new proteins. It is crucial for cell growth, repair, and maintenance. Protein synthesis involves two main steps: transcription and translation.

• Transcription: During this step, the DNA sequence of a gene is transcribed into mRNA (messenger RNA) in the nucleus. This mRNA serves as a template for the next stage.
• Translation: In this step, the mRNA is translated into a sequence of amino acids to form a protein. This occurs in the ribosome, where tRNA (transfer RNA) molecules bring amino acids corresponding to the mRNA codons.

The accuracy of protein synthesis is essential for proper cellular function. Any error in the nucleotide sequence can lead to the production of dysfunctional proteins and potentially harmful mutations. Here is where codon redundancy plays a pivotal role.

If a mutation alters one nucleotide within a codon, redundancy ensures that such a mutation might still result in the correct amino acid being incorporated into the protein. For example, leucine can be encoded by multiple codons (CUA, CUG, CUU, CUC), which means even if one base changes, the resulting codon might still code for leucine, thereby minimizing errors in protein synthesis. This redundancy is a built-in safeguard to maintain the integrity and functionality of proteins.