Chapter 9 Flashcards
anchoring point for proteins (known as cen proteins) that will link the chromosome to the mitotic or meiotic spindle
centromere
condensed DNA
Chromosomes
the end sequences of eukaryotic chromosomes
telomeres
the coiling of a coil.
supercoil
DNA showing only the 1st coil (typically, B form).
relaxed DNA
natural tendency of DNA
supercoiling
enzymes involved in supercoiling
topoisomerases.
properties of DNA that do not change under continuous deformations
(not breaking!) such as twisting, bending, stretching, or binding other molecules
(proteins)
DNA topology
Underwinding can be maintained only
- With a circular DNA with no breaks
- With a linear DNA which is bound to proteins so that there is no end free to rotate
the number of times one closed circular DNA strand is wound about another; the number of topological links holding the circles together
linking number
If dna is interwound in a right handed helix, the linking number is
positive
If the DNA is interwound in a left handed helix, the linking number is
negative
indicates the number of supercoils relative to the number of coils – it is a way of indicating the supercoiled character
of a DNA molecule independent of its length.
superhelical density
enzymes capable of changing DNA topology, particularly inducing or removing supercoils in circular DNA. They vary the Lk.
Topoisomerases:
these enzymes cleave one DNA strand, pass the other around and ligate the broken ends. The
change in Lk goes in steps of +/-1.
Type 1 topoisomerases
