1. DNA

2. DNA is made up of six smaller molecules
a sugar called deoxyribose
a phosphate molecule
four different nitrogenous bases (adenine, thymine, cytosine and guanine).

3. The rails of the ladder are made of alternating sugar and phosphate molecules (sugar phosphate backbone).
The steps of the ladder are made of two bases joined together with either two or three weak hydrogen bonds.
A and T have 2 hydrogen bonds
C and G have 3 hydrogen bonds

4. Nucleotide
The basic building block of DNA is called a NUCLEOTIDE. A nucleotide is made up of one sugar molecule, one phosphate molecule and one of the four bases. 

7. The hydrogen bonds between phosphates cause the DNA strand to twist. 

8. http://www. sciencechannel
sheet/videos/what-is-dna.htm E