Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – , India 1

OC-SBT083-CP1-04 Introduction Programmes and Courses  SEP – SBT083–Unit-01 2

School of Science and Technology, Online Counseling Resource… Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) ‏ Experience: 11 Years 3

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam. 4

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Explain mutations. Describe various types of mutations. Explain mechanisms of various types of mutations. 5

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.6 Introduction - 1 Mutation is defined as heritable abrupt change or changes in the DNA sequence. These inheritable changes in DNA sequences arise spontaneously or can be induced in laboratory using various chemicals or physical agents which are called as mutagenic agents. Mutation may or may not produce any phenotypic change or disease in the organism. In this presentation we will learn in detail the various types of mutations and their mechanism. 6

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.7 Mutations 0n the basis of how the mutations emerge they are broadly classified into two broad types.  Spontaneous mutations:- Arise in the absence of any external mutagenic agent. Arise due to errors in DNA replications.  Induced mutations:- Arise in the presence of known external mutagenic agents. 7

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.8 Spontaneous Mutations-1 The spontaneous mutations arise due to error in DNA replications; number of such errors are corrected during the proofreading by the DNA polymerase enzyme; however some are not corrected and are carried to the next generation. Spontaneous mutations occur due to exposure of DNA to cosmic rays and oxygen radicals. Cosmic rays alter the structure of DNA bases. 8

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.9 Spontaneous Mutations-2 Whereas the oxygen radicals can convert the Guanine into 8-hydroxyguanine causing mutation. Transposon elements cause spontaneous mutations. Transposons cause mutations by inserting into the gene disrupting its sequence.  The spontaneous mutations can arise due to tautomeric shift in nitrogenous bases of DNA. 9

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.10 Spontaneous Mutations-3  Tautomeric shift in nitrogenous base causes transition type spontaneous mutations. 10

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.11 Spontaneous Mutations-4  These types of spontaneous mutations caused due to tautomeric shift in nitrogenous base pair are also described as point substitution mutations. 11

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.12 Induced Mutations-1  Mutations are deliberately produced in laboratories using mutagenic agents are called as induced mutations.  Mutagenic agents are those chemical or energy radiations that cause the mutations.  The examples of chemical mutagenic agents are Base analogues: 5-Bromouracil, 2- Aminopurine. Nitrous acid Alkylating agents: ethyl methane sulfonate, nitrosoguanidine. 12

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.13 Induced Mutations-2  Mutagenic agents:- Intercalating agents:-  Acridine  Ethidium bromide Physical mutagens:-  Ultraviolet radiation  Ionizing radiation such as x rays, cosmic rays, gamma rays. 13

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.14 Induced Mutations-3  Base analogues:- 2-Aminopurine- acts as analogue of adenine but unlike adenine pair with guanine and bring about AT-->GC or occasionally GC-->AT base pair substitution mutation. 5-bromouracil- acts as analogue of thymine and unlike thymine pair with cytosine and bring about AT-->GC or occasionally GC-->AT base pair substitution mutation.  Chemicals:- Nitrous acid reacts with adenine and cytosine and deaminate them causing the faulty base pairing leading to AT-->GC and GC-->AT change. 14

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.15 Induced Mutations-4  Intercalating agents:- Acridine insert between two adjacent base pair increasing the normal distance between the two adjacent base pair which result into the insertion or deletion at the time of DNA replication. Ethidium bromide with the same mechanism that of acridine causes insertion or deletion type of mutations.  Radiations :- Ultraviolet rays cause pyrimidine dimer formation ; these dimers cause replication error leading to deletion type of mutation. 15

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.16 Induced Mutations-5  Radiations :- Ionizing radiations such as x rays, cosmic rays and gamma rays cause ionization of water and other chemicals surrounding the DNA; ionization of water produces hydroxyl radicals these ionized substances then cause mutations into DNA. 16

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.17 Point Mutations-1  A single base pair substitution mutation is called as point mutation. Depending upon the the phenotypic changes caused by such single base pair substitution the point mutations are classified into Silent mutation:-  e.g. UAC-->UAU Missense mutations:-  e.g. UAC-->CAC Nonsense mutations:-  e.g. UAC-->UAG 17

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Insertion and Deletion Mutations-1  Insertion or deletion of single base pair causes shift in the reading frame of nucleotide sequences of DNA leading to expression of wrong polypeptide; these type of mutation is called as frame-shift mutation. 18

School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Significances of Mutations  Mutations leading to variations are used to construct genetic map.  Mutations are used to trace genetic history of organisms.  Mutations are used to study disease gene and understand the mechanisms of development of genetic disorder. 19

School of Science and Technology, Online Counseling Resource… What We Learn…..  Various types of mutations  Mechanisms of various types of mutations.  Significances of mutations. 20

School of Science and Technology, Online Counseling Resource… Critical Thinking Question  Why frequency of spontaneous mutations is lower than the frequency of induced mutations? 21

School of Science and Technology, Online Counseling Resource… Hints for Critical Thinking Question  Proof reading by DNA polymerase  Random event in presence of very low quantity of unknown mutagenic agent 22

School of Science and Technology, Online Counseling Resource… Study Tips  Book Title: Genetics Title: Genetics Author: Monroe W. Strickberger Author: Monroe W. Strickberger Publication: prentice-Hall of India private Limited Publication: prentice-Hall of India private Limited  Book Title: Principles of Genetics Author: Tamarin Author: Tamarin Publication: Tata Mcgrawhills Publication: Tata Mcgrawhills 23

End of the Presentation Thank You ! 24