Eukaryotic Chromosome Structure

Sequence Interspersion

Sequence interspersion - the arrangement of single copy and repetitive DNAs in eukaryotic organisms; the repetitive DNA is usually from the middle repetitive class

Short period interspersion

• The prominent arrangement of single copy and repetitive DNA in eukaryotic organisms
• This arrangement is characterized by:
  • repeated sequences 100-200 bp in length interspersed among single copy sequences that are 1000-2000 bp in length.
• This arrangement is found in animals, fungi and plants. (SC= single copy; R=repeat)

  SC      R      SC      R        SC       R       SC      R       SC
--------XXXXXX---------XXXXXXX-----------XXXXXXX---------XXXXXXX----------
        150 bp                  1500 bp

Long-period interspersion

• This is characterized by:
  • 5000 bp stretches of repeated sequences interspersed within regions of 35,000 bp of single copy DNA
• Drosophila is the principle example of this uncommon sequence arrangement

           Single copy                 Repeat                 Single copy 
---------------------------------------XXXXXXX------------------------------------
           35,000 bp                   5000 bp