translation and transcription

• DNA transcription and translation


  The process by which the genetic code is read by enzymes in order to produce all of the proteins in an organism
• Chromosome


  • A very long molecule consisting of many millions of base pairs
  • Most bases don't do too much
  • Certain portions are called genes and code for different things
• Gene


  • Portions of the chromosome that code for different things
  • In humans, around 10 to 50 thousand base pairs long, with the longest being two-and-a-half million base pairs
  • When a gene is expressed, a specific protein is produced
• Transcription


  1. RNA polymerase uses one of the DNA strands as a template to produce a messenger RNA (mRNA)

  2. RNA polymerase binds to the promoter sequence and pries the two DNA strands apart

  3. The antisense strand serves as the template

  4. RNA polymerase initiates mRNA synthesis at the start codon and moves downstream, synthesizing the mRNA as it goes

  5. Once RNA polymerase reaches the end of the gene, termination occurs and the DNA returns to its original state
• Translation


  1. The mRNA acts as a code for a specific protein

  2. Each set of three bases on the mRNA (codons) codes for a specific anticodon carried by a transfer RNA (tRNA)

  3. Each tRNA is covalently linked to a particular amino acid

  4. The arrangement of the nucleotides into codons is called the reading frame

  5. There are 64 possible codons, more than enough to code for all the amino acids

  6. The ribosome binds to the mRNA and an initiator tRNA, then the tRNAs corresponding to the codons enter the ribosome in sequence, adding amino acids to the growing polypeptide chain

  7. Translation continues until a stop codon is reached, at which point the completed polypeptide is released
• DNA is transcribed into an mRNA, and then this mRNA is translated into a protein, all by obeying the base pairing that occurs in nucleic acids
• Every gene codes for a specific protein, and proteins make up most of what you are, from your muscle tissue and organ tissue, to all of your receptors and enzymes