3.3.1 DNA Structure

DNA is a polymer of Nucleotides1. Sugar (5C)2. Phosphate Group (C-5)3. Nitrogenous Base (C-1)

Phosphate

PentoseSugar

NitrogenousBase

HRibos

e(RNA

)

Deoxyribose(DNA)

2 alternatives

1. Adenine (A)

2. Guanine (G)

3. Cytosine (C)

4. Thymine (T)

5. Uracil (U)

Phosphate

PentoseSugar

NitrogenousBase

1. Adenine (A)

2. Guanine (G)

3. Cytosine (C)

4. Thymine (T)

5. Uracil (U)

DNA

RNA

3.3.2 DNA Structure: Nitrogenous Bases

The phosphate and sugar form the backbone

of the DNA molecule, whereas the bases form

the “rungs”.

The nucleotides within each strand are joined

by covalent bonds.

Alternating sugar and phosphate molecules

form a backbone for each strand.

rungs

bac

kbo

ne

3.3.3 DNA Structure

The two strands are held together by hydrogen bonds between the nitrogenous bases.

3.3.4 DNA Structure

Each Nitrogenous base will only bond with one other specific base.

Because of this complementary base pairing, the order of the bases in one strand

determines the order of the bases in the other strand.

3.3.5 DNA Structure

What is DNA?

Journey into DNA