DNA is a double stranded molecule. Covalent and hydrogen bonds pray important roles in the functioning of DNA molecules.
<em><u>Covalent bonds occur within each linear strand and strongly bond the nucleotide bases, sugars, and phosphate groups occurring both within each component and between components.</u></em>
<em><u> Hydrogen bonds occur between the two strands and involve a base from one strand with a base from the second in complementary pairing.</u></em>
Hydrogen bonds helps the complementary base pairs in DNA; guanine with cytosine and adenine with thymine to connect to one another. The hydrogen bonds between these complementary pairs helps keep the two strands of DNA helix together.
Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism (skototropism).
