1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao C havan Maharashtra Open University, Nashik – 422222, India

2. OC-SBT092-CP1-04 Introduction Programmes and Courses SEP–SBT092–Unit-01-04

3. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) ‏ Experience: 11 Years arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 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.

5. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe different types of genes Describe organization of different types of genes Describe exons and introns

6. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.6 Introduction  Gene is a nucleotide sequence on DNA that codes for a RNA or polypeptide molecule.  However not all genes codes for a RNA or a polypeptide chain of a protein molecule.  Depending upon the various roles that a segment of DNA play in the expression of genetic codes, genes are grouped in various types.  In this module students shall learn about the various types of genes and their genetic functions.

7. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.7 Types of Genes-1  Depending upon the some genetic functions the genes there are various types of genes such as  Structural genes  Exons  Non-coding genes – Introns  RNA genes  Essential genes  Pseudo-genes  Jumping genes

8. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.8 Types of Genes-2  Structural genes:-  A DNA sequence coding for its exact protein product is called as structural genes.  Structural genes can be unique i.e. only one copy of a structural gene can be present in a genome or there may be more than one or two copies of a particular structural gene in the genome.  Structural genes can be identified and characterized with the help of mRNA.  A structural genes is identified by using mRNA- DNA hybridization and translation of such mRNA into protein product and its subsequent identification confirm what gene is coding for which protein product.

9. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.9 Types of Gene-3  DNA –DNA hybridization kinetic and mRNA-DNA hybridization kinetic study show how many copies of a structural genes are there in the genome.  Cot1/2 analysis shows that most of the structural genes lie in non-repetitive segments of DNA molecule.

10. School of Science and Technology, Online Counseling Resource… Types of Genes-4  Pseudogenes:-  Genes which can not be translated into a functional protein are called as pseudogenes.  Pseudogenes are related in their sequences to the functional genes; and show homology with their active gene.  Pseudogenes arise due to mutations in the functional genes affecting signal for initiating transcription, splicing at the exon-intron level and termination of translation prematurely.  A pseudogene contain numerous mutations.  Usually the pseudogenes are located near to their functional genes or interspersed with the active genes. © 2009, YCMOU. All Rights Reserved.10

11. School of Science and Technology, Online Counseling Resource… Types of Genes-5  Pseudogenes:-  Pseudogenes are generated by following mechanisms  Mutations in promoters, stop codons  Retrotransposition –  Small portion of mRNA is reversed transcribed back into chromosome inserting a sequence without promoter.  Duplication of genes and subsequent generation of mutations in it resulting into non-functional gene. © 2009, YCMOU. All Rights Reserved.11

12. School of Science and Technology, Online Counseling Resource… Types of Genes-6  Pseudogenes:-  During viral infection, viral enzyme, reverse transcriptase copy RNA into DNA as copy of DNA or cDNA, but this integrated DNA segment do not become functional gene but become pseudogene since it lack essential sequences for its expression © 2009, YCMOU. All Rights Reserved.12

13. School of Science and Technology, Online Counseling Resource… Types of Genes-7  Jumping genes:-transposons  Transposons are called as jumping genes which move from one location to another in a genome.  Bacterial transposons move by the mechanism involving duplication in which original copy of transposon remain at its original site while other copy appears at another site.  Two copies of transposons at different sites in different chromosomes provide homology for reciprocal recombination; such reciprocal recombination results into deletion, insertions, inversion or translocation. © 2009, YCMOU. All Rights Reserved.13

14. School of Science and Technology, Online Counseling Resource… Types of Genes-8  Jumping genes:- transposons © 2009, YCMOU. All Rights Reserved.14

15. School of Science and Technology, Online Counseling Resource… Types of Genes-9  Jumping genes:- transposons  Transposons possess inverted terminal repeat and produce direct repeats of flanking DNA at their target site. © 2009, YCMOU. All Rights Reserved.15

16. School of Science and Technology, Online Counseling Resource… Types of Genes-10  Jumping Genes:- transposons  Transposons are based upon the mechanisms of their transposition as follow:  Class I transposons – retrotransposons  Retrotransposons duplicate by first transcribed into their corresponding sequence into RNA and then transcribed back into DNA in another site other than its original site by the process of reversed transcription.  Class II transposons:- DNA transposons  these transposons move by the cut and paste mechanism using transposase enzyme from their original site to new site within a genome. © 2009, YCMOU. All Rights Reserved.16

17. School of Science and Technology, Online Counseling Resource… Types of Genes-11  Jumping genes:-  Class I transposons – retrotransposons – groups-  Viral retrotransposons – possess terminal repeats and encodes reversed transcriptase enzyme.  Non–viral transposons do not encodes for reversed transcriptase enzyme and transcribed by RNA polymerase III.  LINEs (Long Interspersed Elements) transcribed by RNA transcribed by RNA polymerase II, lack terminal repeats and encodes for reversed transcriptase enzymes. © 2009, YCMOU. All Rights Reserved.17

18. School of Science and Technology, Online Counseling Resource… Types of Genes-12  Jumping Genes:- transposons:-  Transposons acts as mutagens.  Jumping genes inactivate a functional gene by inserting into it.  Transposons produce deletion, insertion and translocation types of mutations.  Transposons cause chromosomes duplications.  In human transposons are known to cause hemophiliac, severe combined immuno- deficiency. © 2009, YCMOU. All Rights Reserved.18

19. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.19 Exons and Introns-1  Exons:-  The DNA sequences which are represented in mRNA are called as exons.  The exons may be coding sequences or non- coding sequences.  Each exon contain open reading frame that codes for a specific portion of a protein molecule.

20. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.20 Exons and Introns-2  Introns :-  are sequences that are present in DNA but are missing in mRNA.  Introns are also known as interrupted genes.  The introns are removed from the pre-RNA by the process of RNA splicing to produced matured messenger RNA.  Mutations in introns prevent the RNA splicing and thus inhibit the production of matured mRNA.  More than 60% of human genome is composed of intergenic DNA (introns) –of two types – unique and repeated.

21. School of Science and Technology, Online Counseling Resource… Introns  Introns :-  Repeated DNA:- there are two types— 1. Microsatellite DNA:-  composed of very short tandemly repetitive nucleotide sequence of less than 13 bp.  Most of these microsatellite DNA sequences are dinucleotide repeats such as “CACACACACACA”. 2. Genome wide repeats:-  Greater than 100 bp to 1kb  Found as single copy or closely spaced clusters  Known as transposable elements  Unique intergenic DNA:-  30% of the intergenic DNA is unique intergenic DNA.  Unique intergenic DNA composed of nonfunctional relics, non-functional mutant genes, gene fragments and pseudogenes. © 2009, YCMOU. All Rights Reserved.21

22. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.22 Exons and Introns  RNA splicing:-

23. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.23 What We Learn…..  Different types of genes in eukaryotic and prokaryotic cells and their functions.  Exons and introns of structural genes and their functions.

24. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.24 Critical Thinking Question  Why RNA splicing is absent in prokaryotic DNA?

25. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.25 Hints For Critical Thinking Question  Introns

26. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.26 Study Tips  Book Title: Molecular Biology of the Gene Title: Molecular Biology of the Gene Author: Author: Watson, baker et al. Publication: Publication: Pearson Education Ltd. Book Title: Genetics Title: Genetics Author: C. B. Pawar Author: C. B. Pawar Publication: Publication: --

27. © 2009, YCMOU. All Rights Reserved.27 End of the Presentation Thank You !