Chemical mutagens

Mutations

1. Physical and Chemical
Mutagens
Dr. Madhura Mukadam
Associate Professor,
Dept. of Zoology,
Gogate Jogalekar College, Ratnagiri
Dt. 12.10.2017

2. A. Ionizing Radiations
•Theenergycontentofaradiationdependsuponits
wavelength.Shorterthewavelength-greaterthe
energyvalue.
•DNAistheprincipletargetforbiologicaleffects.
•Radiationsbringsabouttheexcitationoftheatom.
(movementofelectronpairfromaninnerorbittoan
outerorbit)
•Inexcitedstatetheatomishighlyreactiveandcalled
asfreeradical.Radiationswhichcapableofgenerating
suchstateiscalledionizingradiations.

3. •RadiationproducesaDNAdamage–nucleotidebase,DNA
singlestrandbreaks(SSBs),Doublestrandbreaks(DSBs)
•AlphaRays:singlestrandbreaksanddeletions.
•Betarays:Betaparticlesareproducedfromphosphorus.They
aresmallandfastmoving.Causeseriousstructuraldamageto
DNAbutlessseverethanalpharadiations.
•Theyoftencausesinglepointdamage.Betarayscause
mutationbybreakingthehydrogenbondbetween
complementarynucleotidebaseinDNA.
•Xraysandgammarays:botharehighenergy
electromagneticradiation.Thesearepacketsofenergy
knownasphotons.TheyindicatesSSBsorDSBstoDNA.

6. B. Non-ionizing radiations
(UV light)
•Theseareelectromagneticradiationswhichdoes
notcarryenoughphotonenergytoionizeatomsor
molecules.
•ThesearelessharmfulforDNAdamage.
•UVradiationsinducedifferenttypesofDNA
damagesamongwhichpyrimidinedimersare
formedwiththehighestfrequency.
•ItblocksDNAreplication

9. Thymine dimercaused by UV light