A codon is a sequence of three consecutive nucleotides in a molecule of messenger RNA (mRNA) that specifies the amino acid to be inserted at that position during protein synthesis. Codons are the fundamental units that direct the translation of genetic information from mRNA into the primary structure of a polypeptide chain.
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Codons are the fundamental units that direct the translation of genetic information from mRNA into the primary structure of a polypeptide chain.
The genetic code is universal, meaning that the same codons specify the same amino acids across all living organisms.
There are 64 possible codons, as each codon is composed of three nucleotides, and there are four possible nucleotides (A, T/U, C, G).
Codons are read in a specific reading frame, where each group of three consecutive nucleotides is interpreted as a single codon.
The anticodon on a tRNA molecule is complementary to the codon on the mRNA, allowing the tRNA to recognize and bind to the correct codon during translation.
Review Questions
Explain the role of codons in the process of translation during protein biosynthesis.
Codons play a crucial role in translation, the process of synthesizing proteins from the genetic information encoded in mRNA. During translation, the ribosome reads the mRNA sequence in groups of three nucleotides, known as codons. Each codon specifies a particular amino acid that is to be incorporated into the growing polypeptide chain. The tRNA molecules, carrying their respective amino acids, bind to the complementary codons on the mRNA, allowing the amino acids to be assembled in the correct order to form the final protein structure.
Describe how the genetic code, as represented by codons, ensures the fidelity of protein synthesis.
The genetic code, as represented by codons, ensures the fidelity of protein synthesis through its universal and unambiguous nature. Each codon specifies a unique amino acid, and this correspondence between codons and amino acids is consistent across all living organisms. This allows the ribosome to accurately translate the genetic information encoded in the mRNA into the correct sequence of amino acids during protein synthesis. The redundancy of the genetic code, where multiple codons can specify the same amino acid, also provides a safeguard against mutations that may not necessarily alter the final protein structure.
Analyze the importance of the reading frame in the translation of mRNA into proteins, and explain how it is maintained during the process.
The reading frame is crucial for the accurate translation of mRNA into proteins. The ribosome must read the mRNA sequence in groups of three consecutive nucleotides (codons) to ensure that the correct amino acids are incorporated into the polypeptide chain. If the reading frame is disrupted, the resulting protein sequence will be completely different, as the codons will be misinterpreted. To maintain the correct reading frame, the ribosome recognizes specific start codons (AUG) that mark the beginning of the coding sequence and then proceeds to read the mRNA in groups of three nucleotides, ensuring that the reading frame is consistently maintained throughout the translation process.
The genetic code is the set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins by living cells.
The anticodon is a sequence of three nucleotides in a transfer RNA (tRNA) molecule that is complementary to the codon on the mRNA and allows the tRNA to recognize and bind to the correct codon during translation.
Reading Frame: The reading frame is the way in which a sequence of nucleotides in an mRNA molecule is read by the ribosome during translation, where each group of three consecutive nucleotides (a codon) is read as specifying a particular amino acid.