What causes the DNA molecule to twist?

Answer 1

DNA twists because of the 3 dimensional structure of the linking molecules along its backbone. These are phosphate molecules and 2-deoxy-D-ribose molecules. The base pairs link to this backbone using covalent bonds but link in the centre using hydrogen bonds. This linking holds the strand in place and supports this twist from both sides. RNA also twists but uses D-ribose instead meaning the twist will be a little different. The links are made from two Purines (double-ringed structures Adenine and Guanine) that attach to Pyrimidines (single-ringed structures Thymine and Cytosine). NOTE: DNA does not have to be double stranded, single stranded DNA is found in the viruses. RNA is usually single stranded but can also be double stranded. The four possibilities are one of the ways various virus families are classified. Try searching DNA in Wikipedia. More There are ten links to the turn (twist) because of the pentagonal symetry of phosphorus in the linking phosphate molecules

Answer 2

Several forces are responsible for the shape and stability of the DNA's twisted ladder shape:

1. Hydrogen bonds hold the sugar-phosphate "rails" together.

2. Hydrogen bonds are the paring forces that hold nitrogen bases together to make the "rungs".

3. Stacking forces hold the stacked nucleotides close together because the nitrogen base parts of nucleotides are hydrophobic (hate water)... DNA is in a watery environment. As the nucleotides are stack together to limit the space (and therefore the water) between them, the molecule must skew itself in order to fit tightly together... hence the twist or helical shape.

Answer 3

A DNA molecule is like a ladder because there are two sides (the sugar-phosphate backbones of the two strands) and rungs (each rung being a pair of complementary bases).

Twisted, because the molecule is twined in a coil called a helix - or rather, a double helix because there are two strands.

For an interactive model of the DNA molecule, use the link below.

Answer 4

Most of the time during a cell's life, the DNA stays unwound as chromatin, only when mitosis or meiosis occurs does it condense into chromosomes. This is so it is easier to separate and, since chromosomes are symmetrical, each new daughter cell will get the same DNA as the original cell. After mitosis (or meiosis) the chromosomes unwind to form chromatin again.

Answer 5

If it wasn't it would be too big for the cell to contain.

Answer 6

It looks like a twisted ladder.

Answer 7

left