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

2. © 2009, YCMOU. All Rights Reserved.2 OC-SBT092-CP1-01 Introduction Programmes and Courses SEP–SBT092–Unit-01-CP1

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 morphology and structure of eukaryotic chromosomes Describe characteristics features of eukaryotic chromosomes

6. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.6 Introduction - 1 DNA encode the all information that living organisms require to comes into his form and grow. Each human cell contain approximately 2 meter long DNA molecule; such long molecule must be accommodated into a microscopic space of nucleus. Therefore the DNA must be compacted by coiling densely. The coiling and compacting of DNA is caused by special proteins called as histone proteins.

7. School of Science and Technology, Online Counseling Resource… Introduction-2 The DNA in eukaryotic organisms is highly organized into a compact threads along with some special proteins; this compact thread of DNA is called as chromosomes. The structure and organization of chromosome help the DNA replicate in correct order and pass into next generation. It is interesting to know therefore the structure and organization of eukaryotic chromosomes formed due to coiling and compacting of DNA molecules by proteins including histones.

8. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.8 Eukaryotic Chromosomes-1 Morphology:- DNA packing in Chromosome

9. School of Science and Technology, Online Counseling Resource… Eukaryotic Chromosomes-2  Morphology:-

10. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.10 Eukaryotic Chromosomes-3  Compacting of chromatins:-

11. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.11 Eukaryotic Chromosome-4 Structure of eukaryotic chromosome: – Eukaryotic chromosome is discrete organized structure made of chromatin. – Chromatin contain DNA, RNA basic proteins such as histone proteins and non- histone proteins. – In chromatin the amount of RNA and non- histone proteins vary from cell to cell. – But histone and DNA are always present in fixed ratio of 1:1. – Because of basic nature of histone proteins, they bind tightly to DNA which is acidic in nature.

12. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.12 Eukaryotic Chromosome-5 Structure of eukaryotic chromosome:- – There are four main histone proteins: H2A H2B H3 H4 – These histone proteins are most conserved proteins known. – The other histone protein is H1. – H1 is involved in maintaining of higher- order folding of chromatin. – Chromatin appears as repeating

13. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.13 Eukaryotic Chromosome-6 Structure of eukaryotic chromosome:- – Chromatin appears as repeating structure of beads of about 10 nm in diameter under electron microscope. – These repeating structure of beads are basic units of chromatin which are called as nucleosomes. – The neighboring nucleosomes appear connected by a thread of DNA called as linker DNA. – The nucleosome consist of 200 bs of DNA, a histone octamer and one molecule of H1 histone.

14. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.14 Eukaryotic Chromosome-7 Structure of nucleosome:- – The DNA strand makes two complete turns around histone octamer; these turns are sealed of by one molecule of H1 histone. – The coiling of DNA strand around the histone octamer compact it seven times or 1 meter long DNA is compacted upto 14 cm wide space. – However the there is not such a big space of 14 cm wide in the nucleus to accommodate therefore the DNA strand coiled around the histone octamers need to be further compacted to accommodate the DNA into 10 to 20 micron space.

15. School of Science and Technology, Online Counseling Resource… Eukaryotic Chromosome-8  Structure of nucleosome:-

16. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.16 Eukaryotic Chromosome-9 Solenoid model of chromatin folding:- – Each nucleosome is flat disk like structure measuring 11 nm in diameter and 5.7 nm in height. – The nucleosomes are compacted by folding into solenoidal structure forming 30 nm thick fibre. – Histone protein H1 and salt play important role in folding the nucleosomes into solenoidal structure. – The explanation of folding of nucleosomes into a solenoidal structure as described above is known as solenoid model of chromatin folding.

17. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.17 Eukaryotic Chromosome-10 Solenoid model of chromatin folding:- Thus DNA strand in solenoid structure formation is compacted 40 times. During the metaphase the chromatin strand with these solenoid structures is further folded 100 times; thus making the packing of chromatin 5000 to 10,000 times.

18. School of Science and Technology, Online Counseling Resource… Eukaryotic Chromosome-11  Characteristics of eukaryotic chromosome:-  Prokaryotic chromosomes are contained by a well defined membrane system- nuclear membrane.  Eukaryotic chromosomes show well defined structures and sub-structures –centromere, telomeres, euchromatins and heterochromatins.  Eukaryotic DNA possess multiple origins of replications.  More than 60% of eukaryotic DNA is composed of intergenic sequences which include repetitive sequences, pseudogenes and non-functional DNA segments.

19. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.19 Eukaryotic Chromosome-12 Types of Chromatin:- There are two types of chromatin Euchromatin:- are transcriptionally active chromatin. During interphase of cell cycle the predominant chromatin present in nucleus is euchromatin which are observed more diffused. Heterochromatin:- are genetically inactive chromatin or chromatin that is not involve in active transcription. Heterochromatins are more condensed at centromeres and telemetric.

20. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.20 What We Learn…..  Morphology of eukaryotic chromosomes  Structures and sub-structures of eukaryotic chromosomes

21. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.21 Critical Thinking Question  Why eukaryotic chromosomes are compacted by various proteins?

22. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.22 Hints For Critical Thinking Question  Larger size  Stabilization and protection of its weak bonds

23. School of Science and Technology, Online Counseling Resource… © 2009, YCMOU. All Rights Reserved.23 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: --

24. © 2009, YCMOU. All Rights Reserved.24 End of the Presentation Thank You !