DNA & Protein


Deoxyribonucleic acid is the hereditary material in humans and most organisms. It is located in the nucleus, and a small amount is located in the mitochondria. In humans, all our DNA is located on 23 pairs of chromosomes. Genes are located on DNA and carry instructions for making proteins. DNA is made of two antiparallel strands that form its double helix structure. Four chemical bases make up DNA: A- adenine, G- guanine, C-cytosine, T- thymine. In humans, there are about 3 billion base pairs. The backbone of DNA is a sugar bonded to a phosphate, referred to as the sugar-phosphate backbone. A nucleotide is the basic subunit of DNA. A nucleotide consists of a sugar, a phosphate, and a base.

Transcription & Translation

Transcription (Nucleus):

  1. In the nucleus, an enzyme called DNA helicase causes the twisted DNA molecule to unwind.
  2. One strand of the DNA is used as the template strand for RNA synthesis.
  3. RNA polymerases begins synthesizing RNA from the DNA template at the promoter sequence (a sequence that lets the RNA polymerase know where to begin).
  4. When RNA is synthesized, it is called mRNA (messenger RNA) and leaves the nucleus and goes to the cytoplasm.

Translation (Cytoplasm):

  1. In the cytoplasm, rRNA (ribosomal RNA), which consists of a small and large subunit, comes together to provide a site for translation to occur.
  2. tRNA (transfer RNA) is the RNA responsible for picking up which amino acid should be added to the chain next.
  3. mRNA, rRNA, and tRNA all come together to perform translation.
  4. mRNA codes for a specific amino acid, tRNA retrieves that amino acid, and rRNA provides a surface for this to occur.
  5. When tRNA brings back the correct amino acid, a polypeptide chain is started.
  6. One amino acid is added at a time, and they are connect with peptide bonds.
  7. When the chain is finished, a protein is formed.


    DNA Introduction. http://www.eurekascience.com/ICanDoThat/dna_intro.htm. 2011 Mar 18.

    2011 Mar 13. What is DNA? Genetics Home Reference. http://ghr.nlm.nih.gov/handbook/basics/dna. 2011 Mar 18.


    http://www.sequencing-gene.com/wp-content/uploads/2010/08/rna-dna.gif. 2011 Mar 18.

    http://www.dna-sequencing-service.com/wp-content/uploads/2010/06/mrna-dna.gif. 2011 Mar 18.


    March 18, 2011

    Brooke Bailey: ebailey@samford.edu

    Biology 306: Bioinformatics

    Samford University


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