Date: December 2004
1.In which direction is the DNA molecule spiralled?
2. How many bases are included in each twist of the DNA molecule?
Actually, DNA can form two right-handed helix shapes (called A and B)
and one left-handed helix shape (called Z). In cells, the B-form is the
most common. It is a right-handed helix that has approximately 10 bases
per turn of the helix.
The DNA molecule is more specifically called a helix which is a spiral
with a constant diameter. It is a right handed helix which means the helix
rotates in a clockwise direction as it moves away from your eye. There are
exactly 10 base pairs for each turn of the helix. For examples of left
handed helices that were printed by mistake, go to
Ron Baker, Ph.D.
The DNA is double stranded. One strand spirals one way and the other strand
spirals the opposite way. The strands are said to be antiparallel. There
are 10 bases in each turn of the helix.
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Update: June 2012