Deoxyribonucleic acid (DNA) structure

DNA

• In the mid twentieth century, geneticists were that DNA (deoxyribonucleic acid) is  genetic material.

• Functions of DNA :

1. It was able to store information for development, structure and metabolism of a cell or organism
2. It was stable so that it could be replicated with high accuracy and transmitted from generation to generation.

• DNA was located in nucleus.

• DNA based on Chargaff's Rule :DNA contains four types of nucleotides, differing in the nitrogen-containing base each contains.

1. The purine base adenine (A)
2. The pyrimidine base cytosine (C)
3. The purine base guanine (G)
4. The pyrimidine base thymine (T)

• A nucleotide from DNA contains one base, one phosphate group, and the sugar deoxyribose.

• DNA based on Franklin’s X-Ray Diffraction Studies : DNA had a helical shape

• DNA based on The Watson and Crick Model : The sugar and phosphate groups are bonded in alternating sequences to form the sides of a twisted ladder. Bases are joined by hydrogen bonds to form the rungs of the ladder.
•  Complementary base pairing occurs,meaning A only bonds with T and G with C.

There are a few level structures of Nucleic Acid.

• 1 structure : the sequence of bases along the pentose-phosphodiester backbone of a DNA                               molecule.                                                                                                                                      -base sequence of bases from the 5' end to the 3' end                                                                              - system notation single letter (A,G,C and T)

• 2 structure: the ordered arrangement of nucleid acid strands which is double helix model.

• 3 structure: three-dimensional arrangement of all atoms of nucleic acid (supercoiling)

• 4 structure: - the structure of chromatin                                                                                                      - each bead is nucleosome(DNA wrapped around histone core)