Who proposed that the structure of dna is a double helix with two polynucleotide chains running in opposite directions and held together by hydrogen bonding between pairs of nitrogenous bases?

James Watson and Francis Crick

Explanation:

James Watson and Francis Crick with few other scientists proposed that DNA is made up of a double polynucleotide chains that are coil/twisted around each other to forming a helical structure. The two DNA chains runs anti-parallel in opposite direction to each other.

Each strand of the DNA is made up of long chain of nucleotides. Each nucleotide contains a sugars (D-ribose), a phosphate group and a nitrogen base forming the backbone of each DNA strand.

They are both DNA strands are held together by hydrogen bond between pairs of nitrogenous bases.

answer:

the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.  

c. live where it’s cold and icy