DNA, the blueprint of life, is read using a system of three-letter codes called codons. Each codon specifies a particular amino acid, the building blocks of proteins. To decipher the DNA code, we follow these steps:
Understanding the Basics
- Directionality: DNA is read in the 5' to 3' direction. This refers to the orientation of the sugar-phosphate backbone of the DNA molecule.
- Codons: The DNA sequence is interpreted in groups of three nucleotide bases, called codons. Each codon corresponds to a specific amino acid.
- Codon Chart: A codon chart (also known as a genetic code table) is used to translate the codon sequence into the corresponding amino acid sequence. You locate the first nucleotide in the codon, then the second, and then the third on the chart to determine the amino acid. The genetic code is degenerate, meaning multiple codons can code for the same amino acid.
- Reading Frames: A double-stranded DNA molecule has six reading frames because both strands are read in the 5′→3′ direction, each with three possible reading frames depending on the starting point.
The Process of DNA Translation
- Transcription: The DNA sequence is first transcribed into messenger RNA (mRNA) by an enzyme called RNA polymerase. This mRNA molecule carries the genetic information from the DNA to the ribosomes.
- Translation: The mRNA is then read by ribosomes in groups of three nucleotides (codons). Each codon is matched to a transfer RNA (tRNA) molecule carrying a specific amino acid.
- Protein Synthesis: The amino acids are linked together in the order specified by the mRNA codons, forming a polypeptide chain. This chain folds into a three-dimensional structure to become a functional protein.
Example
Let's say we have a DNA sequence: 5'- ATG GCT TCA -3'. Using a codon chart and considering only the coding strand, we would break this down into codons: ATG, GCT, TCA. These would be translated into the amino acids: Methionine, Alanine, and Serine, respectively.
Resources
- Several online resources can help you understand and use codon charts, including Khan Academy and Study.com.
- The Genomics Education Programme offers valuable insights into DNA sequencing and interpretation.
