4. Why is DNA referred to as a double helix?

Answer 1

The double helix of DNA has these features:
It contains two polynucleotide strands wound around each other.


The backbone of each consists of alternating deoxyribose and phosphate groups.


The phosphate group bonded to the 5' carbon atom of one deoxyribose is covalently bonded to the 3' carbon of the next.


The two strands are "antiparallel"; that is, one strand runs 5′ to 3′ while the other runs 3′ to 5′.


The DNA strands are assembled in the 5′ to 3′ direction and, by convention, we "read" them the same way.

The purine or pyrimidine attached to each deoxyribose projects in toward the axis of the helix.

Each base forms hydrogen bonds with the one directly opposite it, forming base pairs (also called nucleotide pairs).

Answer 2

In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules. These two long strands entwine like vines, in the shape of a double helix. The nucleotide repeats contain both the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. If multiple nucleotides are linked together, as in DNA, this polymer is referred to as a polynucleotide.

Answer 3

Because double helix is the structure/shape of the DNA...

Answer 4

because dna consists of two sides

Answer 5

Because that is the shape of a chromosome.

Answer 6

because thats the shape its in

go back to middle school

Answer 7

ok turn off the computer and open up your textbook

Answer 8

that is its shape it takes on usually