Biology, Eighth Edition (Raven)

Chapter 4: Cell Structure

Bacterial Chromosome Compaction

How does the packaging of a bacterial chromosome differ from eukaryotic chromosome packaging? Eukaryotic DNA is packaged into chromosomes. Chromosomes are single strands of DNA. Bacterial DNA is packaged into a single chromosome that is a continuous loop. In both cases, the DNA must be folded or coiled so that it will fit into the cell. In bacteria the compaction involves DNA binding proteins that help to form initial loops followed by coiling of DNA. In eukaryotes the DNA is wrapped around groups of histone proteins (collectively called chromatin). The histone groups then combine to form highly condensed structures.

View the animation below, then complete the quiz to test your knowledge of the concept.



1.

To fit within the nucleoid region of a bacterial cell, the chromosome must be compacted about _________ -fold.
A)10
B)100
C)1000
D)10,000
2.

Loop domains compact the DNA about ______-fold.
A)10
B)100
C)1000
D)10,000
3.

DNA toposisomerase I is involved in the formation of _________.
A)the nucleoid region
B)supercoiling
C)loop domains
D)DNA binding proteins
4.

Prior to supercoiling, the bacterial DNA is compacted by the formation of loop domains.
A)True
B)False
5.

DNA binding proteins attach to the supercoils to allow the formation of loop domains.
A)True
B)False
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