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MUTAGENS AND MUTAGENESIS

MUTAGENS AND MUTAGENESIS. Mutagens. Naturally occurring mutations are referred as spontaneous mutations and are thought to arise through chance errors in chromosomal division or DNA replication. Environmental agents which cause mutations are known as mutagens

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MUTAGENS AND MUTAGENESIS

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  1. MUTAGENS AND MUTAGENESIS

  2. Mutagens • Naturally occurring mutations are referred as spontaneous mutations and are thought to arise through chance errors in chromosomal division or DNA replication. • Environmental agents which cause mutations are known as mutagens • These include natural or artificial ionizing radiation and chemical or physical mutagens

  3. Causes of Spontaneous mutations • error in DNA replication • faulty DNA repair e.g. mismatch • natural mutagens

  4. Mutagens • Mutagens could be • Physical • Chemical • Biological

  5. Physical Mutagens • Radiation • Non-ionizing • Ultraviolet (UV) • Ionizing • X-Rays

  6. Chemical Mutagens • Mutagenic chemicals in food contribute to 35% of cancers • Studies showed that certain chemicals such as Formaldehyde, benzene, some type of dyes cause chromosomal breaks and aneuploidy.

  7. Biological Mutagens • Insertion of a transposon (mobile genetics elements has the ability to move and inserted into a gene) within a gene • disrupts the reading frame • loss of function • Antibiotic resistance

  8. Mutagenesis A process by which the genetic information of an organism is changed in a stable manner, either in nature or experimentally by the use of chemicals or radiation

  9. DNA-repair mechanisms • DNA-repair mechanisms exist to correct DNA damage due to: • 1- Environmental mutagens. • 2-Accidental base misincorporation at the time of DNA replication.

  10. DNA-repair mechanisms • There are four different types of DNA-repair mechanisms: • Excision repair • Mismatch repair • Recombination repair system • Double-strand repair

  11. Excision repair system • Excision repair system : removing one strand with damage DNA site. • Excision repair can be • Base-excision repair • Nucleotide-excision repair • The system recognise the damaged site which caused by UV and radiation. • Three protein are important in this process (XPA, XPB, and XPC). • Theses protein detect the damaged site and form which is known as repair protein complex.

  12. Mismatch repair system • Mismatch repair system corrects the errors of replication • Eight gene loci have been identified

  13. Replication repair system • DNA damage interfere with replication and transcription. • In replication: DNA damaged will affect the leading strand • In transcription: DNA damage will affect the process due to RNA polymerase cannot use the leading strand as a template.

  14. Double-strand repair system • Double-strand damage is a common consequence of gamma radiation. • The process require three important genes • ATM (ataxia telangiectasia) • BRCA1 • BRCA2

  15. Thanx

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