文档介绍：Section F
DNA structure and replication
F1 DNA (RNA) structure
F2 Chromosomes
F3 DNA replication in bacteria
F4 DNA replication in eukaryote
Section F1 and G1
DNA (RNA) structure
1. The nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), are polymers of nucleotide units.
DNA consists of four kinds of deoxyribonucleotide units linked together through covalent bonds
Each nucleotide unit is made of a nitrogenous base (the various part in the four different deoxyribonucleotides), a pentose sugar, and a phosphate group.
The nitrogenous base can be adenine (A), guanine (G), cytosine (C), or thymine (T) (uracil (U) in RNA).
The nitrogenous bases are derivatives of two pounds, pyrimidine and purine.
The carbon and nitrogen atoms in the pyrimidine and purine rings are numbered.
The pentose in a deoxyribonucleotide is a deoxyribose, which lacks an oxygen atom at the 2’-position that is present in ribose, the pound.
The deoxyribose is in its b-furanose form (a closed five-member ring).
Only D-deoxyribose is found in DNA.
Deoxyribose and Ribose