DNA and genomics Flashcards
What are the monomers of nucleic acid?
Nucleotides
What are the two types of nucleotides and what do they form when joined together respectively?
Deoxyribonucleotides -> deoxyribonucleic acid (DNA)
Ribonucleotides -> ribonucleic acid (RNA)
What are the structures of nucleotide?
- Pentose sugar
- Ribose and Deoxyribose
- H atom found at 2’ carbon atom in deoxyribose while OH atom found in ribose - Phosphate group
- makes DNA negatively charged - Nitrogenous base
- purines (2 fused ring) : Adenine and Guanine (AG)
- pyrimidines (1-ringed structure) : Cytosine, Uracil and Thymine (CUT)
What is located at the 3’ carbon atom of both DNA and RNA?
OH group
Is DNA or RNA more chemically reactive?
RNA. Presence of extra OH group makes the RNA more polar and reactive.
- so DNA is more stable -> storage of genetic info
- RNA is temporary molecule meant to be broken down
How is the nucleotide formed?
The 3 components are linked up to form a nucleotide via condensation reaction.
What and how is the bond formed when a phosphate group join the pentose sugar?
Phosphoester bond (O-P=O) is formed when phosphate joined the sugar molecule at the 5’ carbon atom via condensation rxn
What and how is the bond formed btw pentose sugar and base?
Glycosidic bond (R-C-O-R) is formed when nitrogenous base is joined to 1’ carbon atom via condensation rxn
How is a polynucleotide formed?
A condensation rxn btw the 5’ phosphate group of one nucleotide and the 3’ hydroxyl group of another to form a phosphodiester bond (O=POOO) and this process is repeated to form a polynucleotide.
What is a sugar-phosphate backbone?
It is made up of alternating sugar and phosphate group with the bases projecting from the backbone.
What is the structure of DNA?
(7 points but only 2 are here)
- DNA molecule consists of 2 polynucleotide strands twisted around each other to form a double helix
- The 2 strands are antiparallel
- One complete turn of the DNA double helix comprises 10 base pairs and spans a distance of 3.4nm. Sugar-phosphate backbone face outside while nitrogenous base faces centre
How are bases joined together btw opposite strands in DNA?
Hydrogen bonding.
Purine always pair with pyrimidine.
A pairs with T to form 2 H bonds while C pairs with G to form 3 H bonds via complementary base pairing.
What is the ratio of pairings btw bases like?
Ratio of A : T is 1 and the ratio of C : G is also 1.
What is the width between the 2 strands of polynucleotides?
Constant width (2nm) btw the sugar phosphate backbone of DNA molecule which equals to the width of a purine and pyrimidine.
What is the bond formed between stacked nitrogenous bases?
Hydrophobic interactions