AM Biologie Notes

Base Excision Repair System removes incorrect or damaged bases from DNA. The main target of base excision repair is nonbulky damage to bases. A group of enzymes called DNA glycosylases play the main role in this method.

Different alkylating agents like Mastard Gas, Ethylmethane Sulfonate, Methylmethane Sulfonate, Nitrosoguanine etc. add alkyl groups to many positions on all four bases of DNA causing DNA damage or DNA mutation. But such damages can be repaired by different types of DNA Alkyl Transferase enzymes. One such enzyme known as Methyl Guanine Methyl Transferase (MGMT) plays an important role that I have mentioned.

DNA can be damaged from sources both inside the cell (replication, reactive oxygen etc.) & outside (UV light, ionizing radiation, mutagens etc.). So you might be wondering how life has managed to survive & thrive for billions of years. The fact is that organisms ranging from bacteria, to humans to plants can efficiently repair their DNA. There are so many mechanisms of DNA repairing but in this video I have discussed Light Dependent DNA Repair/Photoreactivation process.

In this video I have discussed about physical mutagens which are mainly different types of radiation. All forms of life are exposed continuously to radiation. Among the natural sources are Cosmic rays from space, radon & radioactivity from decay of natural radioisotopes in rocks & soil, UV light from sun etc. Man made sources are X rays (for medical uses), cathode ray tube displays (used in order style computer monitors & television sets) etc. But they are mainly classified as ionizing & nonionizing forms. I have tried to discuss all the forms. Watch the full video...

Induced Mutations are alterations in the gene after it has come in contact with Mutagens & Environmental causes. The mutagens are different types - Chemicals, Radiation, Environmental Mutagens, Transposable Genetic Elements etc.

In this video I discussed about different types of Chemical Mutagens. So watch the full video how different types of chemicals induce mutations.