3. Nucleic acids – types and biological role. Chemical composition – structure of nucleotides, chemical bonds. Free nucleotides of biological importance. Features of polynucleotide chains. Watson and Crick model. Primary structure of nucleic acids. Conformation of DNA and of the different types of RNA. Nucleosomes. Histone and nonhistone proteins. Denaturation and renaturation of DNA. Ribozymes, RNA maturation, microRNAs – role in the regulation of gene expression

Describe the main types of nucleic acids and their biological roles. What are the key structural and functional differences between DNA and RNA? Describe the three main types of RNA and their specific roles in protein synthesis.

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Illustrate the chemical composition of nucleotides, including the types of chemical bonds involved. What are the three main components of a nucleotide? What are phosphodiester bonds, and how do they contribute to the structure of nucleic acids?

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List some biologically important free nucleotides and briefly describe their functions.

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Explain the key features of polynucleotide chains, including their polarity. What do the 5′ and 3′ ends of a polynucleotide chain represent?

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Describe Watson and Crick’s model of DNA structure. What are the key features of the double-helix model? How do nitrogenous bases pair in DNA, and what types of bonds hold them together? What is "Chargaff’s rule," and how does it relate to DNA structure?

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Define the primary structure of nucleic acids.

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Discuss the different conformations of DNA and RNA. Describe the three main forms of DNA (A, B, and Z) and their distinctive features. What are the structural differences between rRNA, tRNA, and mRNA?

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Explain the structure and function of nucleosomes. What is the role of histones in forming nucleosomes? What is "linker DNA"? Describe the different levels of chromatin organization.

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Illustrate histone and non-histone proteins and their roles in DNA organization. What are the five classes of histones, and how do their functions differ? How do covalent histone modifications influence gene expression?

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Describe the processes of DNA denaturation and renaturation. What factors can cause DNA denaturation? What is the "melting temperature" (Tm), and how can it be used to study DNA structure? How does DNA renaturation occur?

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What are ribozymes, and provide an example.

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Describe the process of RNA maturation, including the post-transcriptional modifications of rRNA, tRNA, and eukaryotic mRNA. What is the difference between a primary transcript and a mature RNA? What are the functions of capping, polyadenylation, and splicing in the processing of eukaryotic mRNA? Describe the role of snRNA in mRNA splicing.

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Discuss the role of microRNA in regulating gene expression. How does the RNA interference (RNAi) mechanism work? What are siRNAs, and how do they differ from miRNAs?

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How has understanding nucleic acid structure and function contributed to new technologies and medical therapies? Provide specific examples, such as recombinant DNA technology or gene therapy.

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What are the current and future challenges in nucleic acid research, and what potential advancements can we anticipate? For example, consider challenges in gene editing, gene therapy, or developing new antiviral drugs.

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