Genetic Code |
The set of rules by which information encoded in genetic material is translated into proteins. |
Replication and Transcription |
Processes that involve copying a nucleic acid to form another nucleic acid based on complementarity. |
Translation |
Process requiring transfer of genetic information from nucleotides to synthesize a polymer of amino acids. |
Complementarity |
Exists in replication and transcription but not in translation. |
Evidence of Genetic Code |
Changes in nucleic acids lead to changes in amino acids in proteins, suggesting a genetic code. |
Proposition of Triplet Code |
George Gamow proposed that a combination of three nucleotides (triplet) could code for 20 amino acids. |
Codon |
A sequence of three nucleotides that together form a unit of genetic code. |
Number of Codons |
64 codons (4^3 combinations), with 61 coding for amino acids and 3 as stop codons. |
Proof of Triplet Codon |
Developed by Har Gobind Khorana and Marshall Nirenberg through chemical methods and cell-free systems. |
Polynucleotide Phosphorylase |
An enzyme used by Severo Ochoa to polymerize RNA sequences without a template. |
Checker-Board for Genetic Code |
A table showing the codons for various amino acids. |
Codon is Triplet |
61 codons code for amino acids and 3 are stop codons. |
Code is Degenerate |
Some amino acids are coded by more than one codon. |
Codon is Read Contiguously |
Codons are read in mRNA without punctuations. |
Nearly Universal Code |
Codons generally code for the same amino acids across different organisms. Exceptions in mitochondria/protozoans. |
AUG Codon |
Codes for Methionine and acts as an initiator codon. |
Stop Codons |
UAA, UAG, and UGA do not code for any amino acid and signal termination of protein synthesis. |
Wobble Hypothesis |
The third nucleotide of a codon is less specific, allowing some tRNA to pair with multiple codons. |
Redundancy |
Multiple codons can code for the same amino acid, reducing the impact of mutations. |
No Overlapping |
Codons are read one after another without overlapping in the genetic sequence. |
Non-ambiguity |
Each codon specifies only one amino acid or a stop signal, ensuring precise protein synthesis. |
Start Codon |
The codon AUG not only codes for Methionine but also indicates the start of translation. |
Stop Codons Role |
UAA, UAG, and UGA signal the end of translation, ensuring the protein chain is correctly terminated. |
Reading Frame |
The way nucleotides are grouped into codons, starting from the start codon. Shifting the frame alters the protein. |
Codon Usage Bias |
Different organisms prefer certain codons over others, influencing gene expression efficiency. |
Mitochondrial Genetic Code |
Mitochondria have a slightly different genetic code, reflecting their evolutionary origin. |