Packaging of DNA

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

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

Mitochondria have closed circlar DNA (Fig. 9.44).

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


Chloroplast have DNA

• Inverted  repeat of ribosomal, rDNA

 

Activity

Quiz