I. General Characteristic of Nucleic Acids
1. DNA :
Adenine (A), Cytosine (C), Guanine (G), and Thymine (T).
Adenine (A), Cytosine (C), Guanine (G), and Uracil (U).
B. Nucleotides----- Building blocks of DNA
1. Nitrogenous base
a) Purines: Two carbon rings: Adenine (A), Guanine (G)
b) Pyrimidines: One carbon ring: Thymine (T), Cytosine (C), and Uracil (U) for RNA.
2. Five - carbon sugar
a) deoxyribose for DNA: missing an oxygen atom at its #2 carbon.
b) ribose for RNA.
3. Phosphate group: Connecting the 5-Carbon sugars by covalent bond to form the back bone for DNA and RNA.
C. Structure of DNA
1. Cast of Characters:
a) Erwin Chargaff: A== T; G== C, always come in pairs.
b) Maurice Wilkin and Rosalid Franklin published the first X-ray diffraction photograph.
c) Linus Pauling: Three -stranded DNA model.
d) James Watson and Francis Crick
Double Helix Structure, and base pairing rule: G---> C, and A---> T, three hydrogen bonds between G and C,
two hydrogen bonds between A and T.
2. The double helix structure:
D. DNA Replication:
Semi conservative model: something old: parental strand; something new: newly synthesized strand
DNA Polymerase and DNA ligase together are responsible for DNA replication, plus some other enzymatic factors.
Editing out mistakes: nuclease.
Heritable mutations: germ-line cell mutations are heritable.
Value of mutations (mistakes): Evolutionary adaptation.