DNA

Deoxyribonucleic acids

Biopolymer that consists of backbone of alternating units of deoxyribose and phospate.

dna00

dna 0

LEVEL OF STRUCTURE

WORD

1° structure

The sequence of bases along the pentose-phosphodiester backbone of a DNA molecule.

• Base sequence is read from the 5` end to the 3` end

• System notation single letter ( A,T,G and C)

dna10

2° structure

• The DNA model is proposed by Watson and Crick in 1953

• Two strands of polynucleotides for a double helix structure like a spiral

• 3D structure

• Hydrogen bonds link paired bases

• Adenine- Thymine (A-T)

• Guanine-Cytosine (G-C)

• Sugar phosphate backbone is hydrophilic and stays on outside(bases are hydrophobic)

dna 2

3 °structure

• Tertiary structure: the three -dimensional arrangement of all atoms of a nucleic acid super coiling

• Circular DNA: a type of double stranded DNA in which the 5` and 3` ends of each stand are joined by phosphodiester bonds

• Supercoiling: further coiling and twisting of DNA helix

dna 3

4 °structure

• The structure of chromatin

• Each ‘ Bead’ is nucleosome

• Nucleosome consists of :DNA wrapped around histone core

• Histone: a protein, found associated with eukaryotic DNA

• Chromatin :DNA molecules wound around particles of histone in a beadlike structure

dna14