Final answer:
The two types of negative supercoiling are solenoidal and plectonemic, with solenoidal being more efficient for DNA compaction. This enables the lengthy DNA molecules to be packaged tightly within the cell nucleus.
Step-by-step explanation:
The two types of negative supercoiling are solenoidal and plectonemic.
Solenoidal supercoiling involves the spherical twisting of DNA upon itself, resulting in a more compact form. Meanwhile, plectonemic supercoiling is characterized by the DNA coiling back upon its reverse length in the form of pleats. Solenoidal supercoiling tends to be more efficient for DNA compaction because it allows the DNA to be tightly coiled without taking up much space. This form of DNA supercoiling is observed when DNA wraps around histone proteins to form nucleosome structures, which contributes significantly to the compaction of DNA within the cell nucleus.
To fit lengthy DNA molecules inside the comparatively tiny cell nucleus, DNA supercoiling and the use of DNA binding proteins are essential. In the case of eukaryotes, DNA wraps around histone proteins to create nucleosomes, which further coil into a 30-nm chromatin fiber for additional compaction. These processes are crucial as the contour length of double-stranded DNA can be several magnitudes greater than the cell itself, necessitating efficient compaction strategies.