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Introduction to Nucleic Acids and Application to Infectious Disease Detectionn (cont.)

To summarize – DNA is

  • a double stranded helix
  • “rungs” joined together by H bonds
  • phospodiester linkages between 5’ & 3’ ends of nucleotides; 5’ 3’ direction
  • contains deoxyribose sugar
  • contains A, T, C, G nucleotides
  • found in the nucleus of cells; some is found in the mitochondria

RNA is –

  • primarily a single stranded molecule
  • linked by the same type of phosphodiester bonds that join DNA together; 5’ 3’ direction
  • contains ribose sugar
  • contains A, U, C, G nucleotides
  • 3 types of RNA – messenger, ribosomal & transfer (mRNA, rRNA, tRNA)
  • found in the cytoplasm; however it is manufactured in the nucleus, so some is found there

A gene is a sequence of nucleotides that codes for a protein – so a protein is the product of hereditary information.  The human chromosomes -- 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes -- contain almost 6 billion nucleotides – this is called the human genome.  Within these 6 billion nucleotides, there are about 30,000 - 40,000 protein-coding genes. This is a much smaller number than once predicted and is only twice as many as in the worm or fly – which are much smaller organisms than humans!  The gene coding regions in the human actually make up less than 5% of the 6 billion nucleotides.  Some chromosomes have a higher density of genes than others.  The function of the remaining 95% of the DNA is not clear.  Some genes are always expressed, while others are activated when they are needed.


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