DNA Flashcards
DNA
- polymer made up of monomers called nucleotides
- forms a double helix that runs anti-parallel
- four bases: A, T, C, G
Nucleosides
- five carbon sugar (pentose) bonded to a nitrogenous base [base + sugar],
- formed by covalently linking the base to C1 of the sugar
- ex. ATP, ADP
Nucleotides
- contains 3 parts: 5-carbon sugar, nitrogenous base, phosphate group
- formed when one or more phosphate groups are attached to C5 of a nucleoside
- building blocks of DNA
- high energy compounds due to the repulsion between closely associated negative charges on phosphate groups
- ex. AMP, CMP, GMP
What are Adenine’s corresponding nucleosides? Nucleotides?
- Nucleosides: adenosine (deoxyadenosine)
- Nucleotides: AMP (dAMP), ADP (dADP), ATP (dATP)
What are Guanine’s corresponding nucleosides? Nucleotides?
- Nucleosides: guanosine (deoxyguanosine)
- Nucleotides: GMP (dGMP), GDP (dGDP), GTP (dGTP)
What are Cytosine’s corresponding nucleosides? Nucleotides?
- Nucleosides: cytosine (deoxycytosine)
- Nucleotides: CMP (dCMP), CDP (dCDP), CTP (dCTP)
What are Uracil’s corresponding nucleosides? Nucleotides?
- Nucleosides: uridine (deoxyuridine)
- Nucleotides: UMP (dUMP), UDP (dUDP), UTP (dUTP)
What are Thymine’s corresponding nucleosides? Nucleotides?
- Nucleosides: deoxythymidine
- Nucleotides: dTMP, dTDP, dTTP
Ribose
- found in RNA
- nucleic acid (sugar)
- presence of -OH group at C2 which makes it less stable than DNA
Deoxyribose
- found in DNA
- nucleic acid (sugar)
- presence of -H group at C2
What is the backbone of DNA composed of?
alternating sugar and phosphate groups
What is the overall charge of both RNA and DNA?
negative – b/c of the negative phosphate groups
What type of bonds form the sugar phosphate backbone of DNA?
3’-5’ phosphodiester bonds between nucleotides – phosphate group links the 3’ carbon of one sugar to the 5’ phosphate group of next sugar
DNA strands run _____ to one another
antiparallel
What direction do enzymes that replicate and transcribe DNA work in?
3’ to 5’
What is located at the 5’ end of DNA?
-OH or phosphate group boned to C5 of sugar
What is located at the 3’ end of DNA?
free -OH group on C3 of sugar
Purines
- aromatic heterocycle
- contain two rings in structure
- nucleic acid examples: adenine, guanine
Pyrimidines
- aromatic heterocycle
- contain one ring in structure
- nucleic acid examples: cytosine, thymine, uracil
Aromatic Compounds
Compounds must be:
- cyclic
- planar
- conjugated (alternating single and multiple bonds or lone pairs creating at least one unhybridized p-orbital for each atom in the ring)
- fairly unreactive due to delocalization of electrons that form pi electron clouds above and below ring
Huckel’s Rule
- rule followed by aromatic molecules
- has 4n+2 pi electrons
What are the key features of the Watson-Crick Model?
- two strands of DNA are antiparallel (one polarity 5’ to 3’ down and other 5’ to 3’ up)
- sugar-phosphate backbone is outside helix and nitrogenous bases on inside of helix
- A pairs with T via 2 H bonds, G pairs with C via 3 H bonds
- H bonds and hydrophobic interactions between bases provide stability to helix structure
Chargoff’s Rules
- purines and pyrimidines are equal in number in a DNA molecule
- amount of A=T and amount of C=G
B-DNA
- double helix of most DNA is a right handed helix so this is the form it is in
- turns every 3.4nm and contains 10 bases within that span