DNA_RNA_BOH-1.pptx

Biological information: DNA and RNA Presented by Dr Ramin Farahani Faculty of Medicine and Health Slides courtesy of Dr. Christina Adler The University of Sydney Page 1  Lecture Outlines Genetic Information Nucleic Acids Makeup Structure...

Biological information: DNA and RNA Presented by Dr Ramin Farahani Faculty of Medicine and Health Slides courtesy of Dr. Christina Adler The University of Sydney Page 1  Lecture Outlines Genetic Information Nucleic Acids Makeup Structure Function Central Dogma Flow of genetic information Nucleic Acids  Protein Transcription Translation The University of Sydney Page 2  Genetic Information Life depends on the ability of cells to store, retrieve and translate genetic instructions Genetic Instructions are stored as genes Genes are transmitted from parent to daughter cells millions of times during life The University of Sydney Page 3  Genetic Information What form of molecule is capable of accurate replication and directing an organisms development? Deoxyribonucleic acid = DNA What kinds of instructions does the genetic information in DNA contain? Instructions to make PROTEINS Proteins carry out cellular functions All cells have the same DNA but different proteins? Ribonucleic acid = RNA Early experimental work determined that Genetic information is carried by DNA and RNA (Nucleic Acids) Nucleic Acids direct protein production The University of Sydney Page 4 Nucleic Acids The University of Sydney Page 5  Nucleic Acids Nucleic Acids Deoxyribonucleic acid (DNA) = Blueprint, long, many genes Ribonucleic acid (RNA) = Transmission, short, few genes The University of Sydney Page 6  Nucleic Acids – What do you think of when you hear the word DNA? The University of Sydney Page 7  Makeup of Nucleic Acids DNA and RNA are polymers of repeating subunits, called nucleotides Nucleotides (http://sydney.edu.au/library) 1. 5-Carbon Sugar 2. Phosphate Group 3. Nitrogenous Base IMAGE DNA, RNA, and Protein Molecular Biology. Pages 62-93. © 2013. Figure 3.01 The Order of the Nucleotides Encodes the Genetic InformationNucleotides are ordered along a string of DNA The University of Sydney Page ordering of the different nucleotides that dictates the nature of the information within the nucleic acid.8  Makeup of Nucleic Acids DNA and RNA are polymers of repeating subunits, called nucleotides Nucleotides (http://sydney.edu.au/library) 1. 5-Carbon Sugar DNA = deoxyribose (http://sydney.edu.au/library) RNA = Ribose IMAGE 2. Phosphate Group DNA, RNA, and Protein Joined to 5’ carbon Molecular Biology. Pages 62-93. © 2013. Backbone Figure 3.03 3. Nitrogenous Base The Sugars Composing RNA and DNARibose is the five-carbon sugar (pentose) it has one less oxygen than ribose as it has hydrogen in place of the hydroxyl group The University of Sydney Page 9 Copyright © 2015 Elsevier, Inc. All rights reserved.  Makeup of Nucleic Acids DNA and RNA are polymers of repeating subunits, called nucleotides (http://sydney.edu.au/library) Nucleotides 1. 5-Carbon Sugar 2. Phosphate Group 3. Nitrogenous Base DNA = Adenine (A), Guanine (G), Cytosine (C) and Thymine (T) IMAGE RNA = Adenine (A), Guanine DNA, RNA, and Protein Molecular Biology. (G), Cytosine (C) and Uracil (U) Pages 62-93. © 2013. Figure 3.05 Purines = A and G The Bases of the Nucleic AcidsThe four bases of DNA are adenine, guanine, cytosine, and thymine. In RNA, uracil replaces thymine. Pyrimidine bases contain one-ring structures, whereas purine bases contain two-ring structures. Pyrimidines = T, C and U Bacteria = Streptococcus gordonii Copyright © 2015 Elsevier, Inc. All rights reserved. The University of Sydney Page 10  Structure of Nucleic Acids (http://sydney.edu.au/library) – Polarity – Free phosphate 5’ end – Free hydroxyl 3’ end – Reading direction 5’ to 3’ – Structure – RNA = single stranded IMAGE DNA, RNA, and Protein Molecular Biology. – DNA = double The University of Sydney Pages 62-93. © 2013. Page 11 Figure 3.06  Double Helix: DNA History – Watson and Crick 1953 – X-ray Diffraction – Nobel Prize, 1962 ‘for their discoveries concerning the molecular structure of nucleic acids and its significance for information transfer in living matter’ – Rosalind Franklin took the x-rays showing DNA double helix The University of Sydney Page 12  Double Helix: DNA (http://sydney.edu.au/library) Complementary Base Pairing – Inside = Complementary Base pairing – A : T = 2x hydrogen bonds – G : C = 3x hydrogen bonds – Outside = Sugar-Phosphate (http://sydney.edu.au/library) backbone – Kept equidistance due to internal complementary base pairing IMAGE – Wind around each other, DNA, RNA, and Protein Molecular Biology. complete turn every 10 base Pages 62-93. © 2013. pairs Figure 3.11 Base Pairing by Hydrogen Bond FormationPurines (adenine and guanine) pair with pyrimidines (thymine and cytosine) by h – Strands are anti-parallel and bonding (colored regions). When the purines and pyrimidines first come together, they form the bonds indicated by the dotted li complementary Copyright © 2015 Elsevier, Inc. All rights reserved. The University of Sydney IMAGE Page 13 DNA, RNA, and Protein  DNA Replication and Double Helix During each cell division, the cell must copy its DNA and it pass on to daughter cells (http://sydney.edu.au/library) – DNA Replication – Each strand contains a complementary partner – Separate into two strands – Heat induced denaturation – DNA polymerase copies each strand to make new complimentary strand – Replicates all genes – Cell divides, each daughter cell receives a copy of the parental DNA The University of Sydney IMAGE Page 14 DNA, RNA, and Protein  Question – What would the complimentary strand of DNA be for the following sequence? 5’-TTGCACCTA-3’ The University of Sydney Page 15  The Genome Complete set of information of an organisms DNA – Caries information for – Gene expression = RNA – Protein synthesis – Huge amount of information – 3.0 x 109 base pairs of DNA – 20,000 – 25,000 genes – Genes account for 2% genome – 98% Non-coding DNA – Non-coding DNA contains repeating sequences (50%) – Repeating sequences important in maintaining structure of DNA The University of Sydney Page 16  Packaging of the Genome – Problem 2 meters of DNA per cell Cell nucleus 6μm (1.0000×10−6 m) – Solution = Chromosomes DNA wrapped around proteins called Histones DNA + Histones = Chromatin Chromatin further wound up Centromere = center Telomere = ends, aging and cancer The University of Sydney Page 17  Karotype Karotype = complete set of chromosomes (http://sydney.edu.au/library) IMAGE DNA, RNA, and Protein Molecular Biology. Pages 62-93. © 2013. The University of Sydney Page 18 Figure 3.18  Questions – Which of the following statements is true regarding histone proteins? A. Histone proteins are important to stabilise single stranded RNA B. DNA associates with histone proteins to form chromatin C. Histones are made up of DNA The University of Sydney Page 19 Central Dogma The University of Sydney Page 20  Central Dogma Central dogma describes the flow of genetic information during cell growth and replication (http://sydney.edu.au/libr DNA  RNA  Protein Information doesn’t flow backwards Proteins = ‘gene products’ Some RNA = ‘gene products’ Transcription = DNA directed synthesis of RNA Translation = synthesis of IMAGE proteins from RNA DNA, RNA, and Protein The University of Sydney Page 21 Molecular Biology.  Transcription DNA directed synthesis of RNA (http://sydney.edu.au/library) DNA  RNA Same Language DNA = long RNA = short Only contains few genes IMAGE DNA, RNA, and Protein These genes will Molecular Biology. Pages 62-93. © 2013. produce a protein Figure 3.21 The University of Sydney Differing Patterns of TranscriptionIn eukaryotes, each gene is transcribed to give a separate mRNA that encodes only Page 22 a single protein. In prokaryotes, an mRNA molecule may carry information from a single gene or from several genes that are next to each other on the chromosome.  Transcription DNA directed synthesis of RNA Unwinding of DNA double helix Template strand Complimentary base pairing RNA polymerase to form RNA What base would be in the RNA sequence that wouldn’t be in the DNA sequence being copied? The University of Sydney Page 23  Different Types of RNA mRNA tRNA rRNA MicroRNA Gene Protein synthesis Ribosomes Gene expression information regulation The University of Sydney Page 24  Translation Synthesis of proteins from RNA Translation of a mRNA (http://sydney.edu.au/library) nucleotide sequence into amino acids, which is a different language How is the information from a strand of RNA translated into a chemically different set of subunits, amino acids in IMAGE DNA, RNA, and Protein proteins? Molecular Biology. Pages 62-93. © 2013. The University of Sydney Figure 3.21 Page 25 Differing Patterns of TranscriptionIn eukaryotes, each gene is transcribed to give a separate mRNA that encodes only a single protein.  The Genetic Code Problem – 4 Different RNA bases: A,G,C,U – 20 different amino acids Solution – Genetic Code – Dictionary that links a sequence of RNA to an amino acid – Codon = 3 x RNA bases = 1x amino acid The University of Sydney Page 26  Genetic Code Mutations 1. Silent Mutations Codon containing a changed RNA base but codes for the same amino acid 2. Missense Mutations Codon contains a changed RNA base, producing a different amino acid 3. Nonsense Mutations Codon containing changed RNA base results in a termination codon e.g. Duchene’s muscular dystrophy caused by nonsense mutation in dystrophin gene The University of Sydney Page 27  Components for Translation – mRNA – Amino acids – tRNA = Adapter molecules – Ribosomes = Action stations – Enzymes and energy The University of Sydney Page 28  tRNA = Adapters mRNA doesn’t recognise the amino acids specified in their sequence tRNA – Adapter – Recognises both the mRNA and amino acids – Humans have approximately 50 tRNAs, however only 20 amino acids – More than one tRNA per amino acid – Structure is cloverleaf – Attachment for amino acid – Contains 3 base pair anti-codon, which is complimentary to the codon in mRNA sequence The University of Sydney Page 29  Ribosomes = Action Site Ribosomes are where the mRNA is translated into a protein (http://sydney.edu.au/library) Ribosomes – Large complex: Protein and rRNA – 2 x Subunits – Small Subunit: a. binds mRNA b. Links codon in RNA with anti-codon in tRNA – Large Subunit: a. Catalyses formation of peptide bonds, IMAGE linking amino acids to form protein DNA, RNA, and Protein Molecular Biology. The University of Sydney Pages 62-93. © 2013. Page 30 Figure 3.26  Questions – How many RNA bases in a codon? A. 5 bases B. 7 bases C. 3 bases – What are the major differences between DNA and RNA? DNA RNA Number of strands Bases Length (Long vs Short) The University of Sydney Page 31  Summary – Genetic information (genes, flow of information between nucleic acids and proteins) – Nucleic Acids (DNA/RNA, chemical structure of bases, DNA double helix, DNA replication, DNA genome) – Central Dogma (Direction of information flow, transcription DNA to RNA, translation RNA to proteins, the genetic code and components of translation). The University of Sydney Page 32  Readings and Contact Information Readings – ‘Molecular Biology’ by David Clark, Chapter 3 ‘DNA, RNA, Protein’ – This textbook is available via Sydney University’s library as an online textbook. Contact – Please feel free to ask questions – [email protected] The University of Sydney Page 33  Antimicrobials and Bacterial Translation – Antibiotics targeting bacterial infections in humans, take advantage of differences between protein Antibiotic translation in bacteria andEffect humans Streptomycin Inhibits initiation and causes misreading Tetracycline Binds to the 30S subunit and inhibits the binding of tRNAs Erythromycin Binds to the 50S subunit and inhibits translocation The University of Sydney Page 34  Transcription DNA directed synthesis of RNA – Initiation – Starting point = Promoter (TATA) on gene, RNA polymerase binding site – Open up DNA double helix – Elongation – RNA polymerase moves stepwise along the DNA – Adding RNA bases complementary to DNA – Termination – Stopping Point = Poly A, Displaces RNA polymerase – End product = single stranded RNA The University of Sydney Page 35