Hopefully this is right, it was first year stuff so double check if you can
DNA =
-It is formed of monomers called nucleotides
-These nucleotides are formed of three parts - a five carbon sugar (pentose sugar), a phosphate group and a nitrogenous base
-in DNA the five carbon sugar is called deoxyribose
-the nitrogenous base can be one of four types in DNA these are; adenine, guanine, cytosine and thymine
-each nucleotide is joined together by a covalent bond
-the covalent bond is between the phosphate group of one nucleotide and the third carbon atom of the pentose sugar in the next
-when many nucleotides are joined together this forms a sugar phosphate backbone (a nucleotide chain)
-DNA is formed of two nucleotide chains
-these nucleotide chains are joined together by hydrogen bonds between the corresponding nitrogenous bases (A=T and C=G)
-this forms a ladder like structure
-due to the nature of these bonds the DNA forms a helix (twisted structure)
-that is why DNA is referred to as having a double helix structure
RNA =
-RNA has the same basic structure to DNA
-it is also formed of nucleotides which follow the same structure the nucleotides are also joined together by covalent bonds in the same way that DNA is
-There is however one key difference - the pentose sugar is ribose
-Also it does differ when it comes to the nitrogenous bases. Thymine is replaced with uracil. So the nitrogenous bases in RNA are adenine, guanine, uracil and cytosine
-RNA is also single stranded as its role is in protein synthesis (you may learn about other roles during your A level depending on your course)
-RNA is single stranded as it must leave the nucleus to enter the cytoplasm during protein synthesis (as DNA is too large to leave it)
-RNA also follows the same base pairing rules as DNA. The nitrogenous bases are hydrogen bonded together with the same base pairs (A-T, G-C)
Basically DNA and RNA are pretty much the same Other than the key three differences (RNA is single stranded, RNA has a ribose sugar instead of deoxyribose and RNA nucleotides have a uracil base rather than thymine)
Their phosphates, sugars and bases show the same bonding patterns to form nucleotides and their nucleotides bind to form nucleic acids in the same way
Let me know if that's any help at all or you have any other questions!