Introduction to Molecular and Cell Biology, Biol. 220 Lecture 12: Chromosomes
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Bacterial chromosomes

• Circular (Fig. 9.27) .
  Fig. 9.27
  
  
• Assembled around a protein scaffold (Fig. 9.28).
  Fig. 9.28
  
  
• Supercoiled.
• Negative charges neutralized by spermine, H-NS, and other non-histone proteins.
• Single origin of replication.
  

Eukaryotic chromosomes

• Some circular and some linear.
• Assembled around a protein scaffold (Fig. 9.34).
  Fig. 9.34
  
  
• DNA wrapped around histone proteins to form nucleosomes (Fig. 9.30).
  Fig. 9.30
  
  
  
• Nucleosome associated DNA is folded into higher order structures around protein scaffold (Fig. 9.35)
  Fig. 9.35
  
  
  (Movie).
  

  Movie showing the heirarchal packaging of chromosomes.

  
  

• Multiple origins of replications.
• Chromosomes have centromeres to which spindle fibers (microtubules) attach during nuclear division
• Linear chromosomes have telomeres that serve as a buffer region to protect the ends of the DNA (found to be related to aging of cells).  Telomerase responsible for maintaining ends.
  

Organelle Chromosomes

Mitochondria have closed circlar DNA (Fig. 9.44).
Fig. 9.44

• Abberations in the standard genetic code (Table 9.4) in mitochondria.
  Table 9.4
  


Chloroplast have DNA

• Inverted  repeat of ribosomal, rDNA
  
  

 

 

Created 2004 by CA Rinehart• email CA Rinehart

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