RNA Structure & Function Lecture Notes PDF

BMS: 141 Lecture No: 7 Title: RNA Structure & Function Instructor Name: Dr Amira Abdel Haleem Medicine and Surgery Program Fall 2024  Intended Learning Outcomes of lecture At the end of this l...

BMS: 141 Lecture No: 7 Title: RNA Structure & Function Instructor Name: Dr Amira Abdel Haleem Medicine and Surgery Program Fall 2024  Intended Learning Outcomes of lecture At the end of this lecture, the students will be able to: 1. Define RNA 2. Identify the structure of RNA. 3. Identify the different types of RNA. 4. Identify the functions of different types of RNA. 5. Differentiate between DNA and RNA.  RNA Def.: Single long chain of repeating ribonucleic acid.  Function of RNA RNA molecules are formed in the nucleus under the control of DNA. RNA molecules are involved in protein synthesis.  Types of RNA ♒ There are 3 main types of RNA: o messenger RNA = mRNA. o transfer RNA = tRNA. o ribosomal RNA = rRNA.  Messenger RNA (mRNA ) Messenger RNA (mRNA) comprises only about 5% of the RNA in the cell. The mRNA is synthesized in the nucleus as a complementary strand to the template strand of DNA. Function of mRNA: mRNA copies one segment (gene) on one strand of DNA in the nucleus and carries that information to the ribosome in the cytoplasm, where it directs synthesis of a specific protein.  Messenger RNA (mRNA ) Each 3 successive bases in the mRNA are called a “codon” because they code for a specific amino acid. The first codon (at 5` end) do not code for amino acid, is called initiating codon. The last codon (at 3` end) do not code for amino acid, is called the and stop codon.  Messenger RNA (mRNA ) It is used as a template for protein synthesis Sub-entities of mRNA: - Monocystronic : mRNA carries information from only one gene (characteristic of eukaryotes) -Polycystronic: mRNA carries information from more than one gene (characteristic of prokaryotes) Structure of mRNA: The nucleotide sequence of RNA are divided into: - Protein coding region: Which carries information about the protein coded by the gene - Untranslated regions: at its 5’ and 3’ end  Transfer RNA (tRNA) This type of RNA forms about 15% of the cell's RNA. It is the smallest RNA. There are at least 31 tRNA; some amino acids have more than one tRNA.  Structure & Function of tRNA It fold into 3 dimensional structure by forming base pairs between different regions of the molecule producing a molecule like a clover leaf. tRNA brings the appropriate amino acid to the mRNA. Anticodon: a series of 3 nucleotides that are the complement of the codon. Each anticodon has its specific amino acid.  Ribosomal RNA (rRNA) The rRNA is the nucleic acid present in ribosomes. rRNA forms about 80% of the RNA of the cell. It is synthesized in the nucleolus. Function of Ribosomes: - Ribosomes are the sites of protein synthesis. - On the surface of ribosomes, the mRNA & tRNA interact to synthesize protein molecule.  Structure of Ribosomes Ribosomes are large complexes of protein and rRNA The mammalian ribosome consists of 2 subunits: -The larger subunit is known as the 60 S subunits -The smaller subunit as the 40 S subunits (S = Svedberg units = sedimentation rate of each subunit). The ribosome has three binding sites for tRNA molecules: - A sites - P sites - E sites Differences between DNA and RNA  As Regard tRNA, which of the following statements describes its function? a) It is the machinery for protein synthesis b) Carrying amino acids to the site of protein synthesis c) It stores the genetic information d) Peptide bond formation Answer: b  Which of the following types represents 80% of total RNA? a) mRNA Answer: c b) tRNA c) rRNA d) microRNA Which of the following carries genetic codes of a gene from nucleus to cytosol? a) tRNA b) Histones Answer: c c) mRNA d) Ribosomal RNA  Which type represents 5% of total RNA? a) mRNA b) rRNA c) tRNA Answer: a d) microRNA Enumerate differences between DNA and RNA.  References Lippincott’s illustrated reviews, Biochemistry, 6th edition, 2014. BRS Biochemistry, Molecular Biology and Genetics, 5th edition, 2010. Chatterjea’s Textbook of Medical Biochemistry, 8th edition. Vasudevan's Textbook of Biochemistry For Medical Students, 6th Edition. THANK YOU