§4.1 DNA Damage (DNA 损伤)
DNA damage: Abnormal change on chemical structure of
DNA.
1. Causes of mutation
★Chemicals
2. Types of damage to DNA
★（单碱基改变）
★（双碱基改变）
★（DNA链断裂）
★（交联）
3. Consequences of DNA damage
★a. Point mutation (mismatch)-碱基替换
·Case1: 镰刀形红细胞贫血（ sickle cell anaemia ）
★b.Frame-shift mutation-框移突变
★c. Rearrangement-重排
1. Site-specific recombination
2. Homologous genetic recombination
3. DNA transposition
基因易位—Burkitt淋巴细胞瘤
★d. Dynamic mutation-动态突变
三核苷酸重复扩展（ trinucleotide repeat expansion ）突变
Huntington’s disease
使基因组具有遗传的不稳定性
3.Consequences of mutation
★a natural evolution - a diversity of the biological world.（多样性和进化）
★Changes of genotype, but no effect on phenotype. （不改变表型）
★the functional alternation of biomolecules, death of cells or tissues, or some diseases as well. （致病或致死）
