DNA Replication and Protein Synthesis PDF

DNA replication and protein synthesis PHRM 105 General Biology Prepared by Dr Abdulrahman Aljabri ‫كليــة الصيدلة‬ Outline 1. Introduction Be the end of this session, students should be able to: 2. Genetic materials Nucleic...

DNA replication and protein synthesis PHRM 105 General Biology Prepared by Dr Abdulrahman Aljabri ‫كليــة الصيدلة‬ Outline 1. Introduction Be the end of this session, students should be able to: 2. Genetic materials Nucleic Define the DNA and RNA acid (DNA and RNA) List the difference between DNA and RNA 3. DNA replication Demonstrate the DNA replication 4. Repair Describe the DNA replication steps mechanism Describe the protein synthesis 5. Protein Synthesis List the basic difference between (Transcription & translation ) nucleic acid and protein 1. Introduction  Molecular structure of the genetic material:  Until 1940: Protein is the genetic material.  Discovery of DNA as Genetic Material (1952): Scientists Hershey and Chase proved that DNA, not proteins, carries genetic information, showing that DNA is the key to inheritance.  Watson and Crick’s DNA Model (1953): Watson and Crick discovered the double-helix shape of DNA, explaining how genetic information is passed from one generation to the next. ‫لإلطالع‬ 2. Genetic materials (Nucleic acid( Nucleotide Nucleic acids are found in two basic structural Base forms: 1- Deoxyribonucleic acid Phosphate (DNA). 2- Ribonucleic acid (RNA). Sugar Nucleotides are A building blocks Nucleotide of nucleic consists of:acids. X=H: DNA (deoxyribose) 1. Nitrogenous base, X=OH: RNA (ribose) 2. Pentose sugar, 3. Phosphate group. 2. Genetic materials (Nucleic acid( Nitrogen bases of DNA and RNA: Purines Five kinds of nitrogenous bases: Purine bases Pyrimidine bases (DNA & RNA) Pyrimidines thymin (DNA & e RNA) (DNA) 2. Genetic materials (Nucleic acid( DNA Structure: DNA Composed of (2) polynucleotide chains twisted C G A T into a helical shape T A Sugar-phosphate backbone C G Phosphate – Sugar-phosphate backbone is A T G C group (outside) A G A Nitrogenous base Nitrogenous base A T Covalent (can be A, G, C, or T ) bond Sugar – Nitrogen bases are G C T A joining C C T A nucleotides perpendicular to the backbone C G (inside) T A DNA Thymine (T) A DNA T nucleotide T double helix Phosphate – Pairs of bases give the helix a group uniform shape G G Sugar (deoxyribose ) – A (Adenine) pairs with T G G DNA nucleotide (Thymine), G (Guanine) pairs with C (Cytosine) Two representations of a DNA polynucleotide  2. Genetic materials (Nucleic acid( Three presentations of DNA and complement pairing Adenine pairs with Thymine Two hydrogen Hydrogen bond bonds A T Base pair Cytosine pairs with Guanine Three hydrogen bonds C G Ribbon model Partial chemical structure Computer model 2. Genetic materials (Nucleic acid( Comparison between DNA and RNA Feature DNA RNA Number 2 1 of strands in molecule Type of Deoxyribos ribose sugar in e nucleotid e Nitrogeno A,C,G,T A,C,G,U us bases contained Basic Nucleotide Nucleotide subunits Nucleotid Sugar, Sugar, e base, base, This Presentation is NOT an Alternative to the Textbook! 2nd semester 2020/2021 componen phosphate phosphate ts 3. DNA replication What is DNA Replication? DNA Replication is the process of making a copy of the genetic information contained in DNA and is catalyzed by a type of enzyme called DNA polymerase. Why is this process necessary? -Cell division -the transfer of genetic information from one generation to the next. -Renew cell How does DNA Replication occur? DNA Replication occurs through the semi-conservative mechanism, where each strand of the DNA double helix acts as a template for the synthesis of a new complementary strand.  3. DNA replication DNA replication proceeds in two directions at DNA replication begins at the One many sites simultaneously origins of replication. Parental DNA Origin of Parental strand DNA unwinds (open) at the origin molecule replication Daughter strand to produce a “bubble,” Replication proceeds in both directions from the origin, “Bubble” Replication ends when products from the bubbles merge with each other. Eukaryotic DNA has many origins to start replication simultaneously, shortening the total time. Two daughter DNA molecules This Presentation is NOT an Alternative to the Textbook! 2nd semester 2020/2021  3. DNA replication (Semiconservative model) The two DNA strands A T separate G C A T Parental DNA Each strand (from parent Parental strand used as a pattern A T T A molecule molecule) is used as a Daughter strand used as Daughter pattern to produce a complementary strand strand Parental complementary strand, strand using specific base pairing. Each new DNA helix has one old strand with one new Daughter DNA strand molecules DNA replication follows a This Presentation is NOT an Alternative to the Textbook! 2nd semester 2020/2021 semiconservative model. 3. DNA replication DNA replication steps: 1. Untangles and relieves DNA stress by DNA Topisomerase. 2. Unzips DNA strands by Helicase. 3. Add RNA primer by primase, as starting point for DNA polymerase to begin synthesis of the new strand. 4. Adds complementary nucleotides by DNA polymerase. 5. Check and correct mistakes by DNA polymerase. 6. Seals gaps in DNA strands by DNA the leading continuousling strand is synthesized and the lagging strand is synthesized in fragments called ligase. Okazaki fragments. ‫لإليضاح‬ 3. DNA replication DNA Replication Significance End product: Two double-stranded DNA molecules, each with one new and one old strand. DNA replication occurs before cell division, ensuring identical genetic information in all cells. Essential for inheritance: Offspring receive identical DNA copies.  3. DNA replication When things go wrong… during DNA replication! Mutations: changes in the DNA sequence, that may be passed along to future generations. Point mutations: a single base substitution GCTACCGGTC GCTACCGCTC Deletion: a small DNA segment is lost Insertion: a segment of DNA is added Frame-shift mutation: modification of the reading frame after a deletion or insertion, resulting in all codons downstreams being different. 4. Repair mechanism Repair Mechanisms Mismatch Repair Base Excision and Proofreading by Nucleotide Excision DNA Polymerase DNA polymerase Repair Corrects replication errors by Corrects mismatched base Repairs single-base errors checking and fixing incorrectpairs left after DNA and larger DNA structural nucleotides immediately. replication proofreading. distortions efficiently. 5. Protein Synthesis A gene: a specific sequence of a DNA that directs the synthesis of a specific protein. How ?? This is through CENTRAL DOGMA and protein synthesis 1 2 Transcription Translation Prote DNA RNA ins 5. Protein Synthesis 1. Transcription: DNA  RNA Where: Transcription occurs in the nucleus. Step 1: DNA unwinds in one part. Step 2: mRNA is made by matching bases with the DNA strand. Step 3: mRNA takes the instructions from the DNA to the ribosome to make a protein. 5. Protein Synthesis 2. Translation Translation: Making a protein using the code in mRNA. RNA  In other word, switching from the nucleotide “language” Protein to amino acid “language” Where: Occurs at the ribosome in the cell's cytoplasm. Ribosomal RNA (rRNA): Helps mRNA attach to the ribosome for protein synthesis. Transfer RNA (tRNA): Delivers the right amino acids to the ribosome to build the protein. 5. Protein Synthesis Transfer RNA (tRNA) Transport molecule that carries specific amino acid to a ribosome. Each tRNA recognizes the correct codon on the mRNA molecule. A codon: consisting of (3) nucleotides Each amino acid is specified by a codon 5. Protein Synthesis Translation steps Step 1: mRNA leaves the nucleus and goes to the ribosome. Step 2: mRNA attaches to the small ribosome subunit. Large subunit Step 3: tRNA brings an amino acid to the ribosome Small protein subunit ribosome ribosome; its anticodon matches with the mRNA mRNA codon. Step 4: Amino acids link together to form a growing protein chain. Step 5: tRNA without an amino acid leaves the ribosome. Step 6: More tRNAs bring amino acids until the protein is complete. 5. Protein Synthesis Summary transcription translation Definition Purpose Products Location protei n Name 3 different RNA molecules involved in protein synthesis? 1. mRNA (messenger RNA) ---- transcription 2. rRNA (ribosomal RNA) ----- translation 3. tRNA (transfer RNA) --------- translation  Comparison of Nucleic Acids (DNA and RNA) and Proteins Category Nucleic Acids Nucleic Acids Proteins (DNA ) (RNA) Basic Unit Nucleotides Nucleotides Amino Acids Primary Function Genetic information Genetic information Catalysis of storage and storage and biochemical transmission transmission reactions, structural roles, signaling, and more Structure Double-stranded Single-stranded Primary, secondary, helix tertiary, and quaternary structures; complex folding Components Deoxyribose sugar, Ribose sugar, 20 standard amino Nitrogenous bases Nitrogenous bases acids (A, T, G, C), (A, U, G, C), phosphate phosphate