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Dna replication.
This document provides an overview of molecular biology and DNA replication. It defines molecular biology as the branch of biology dealing with macromolecules essential to life like nucleic acids. Nucleic acids are composed of nucleotides with a pentose sugar, phosphate group and nitrogenous base. DNA contains the genetic instructions and is replicated before cell division in a semi-conservative process where the parental DNA strands separate and each acts as a template for a new complementary strand. DNA replication involves enzymes like DNA polymerase and helicase and occurs through initiation, elongation and termination steps to produce two identical copies of DNA.
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Dna replication.
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- 3. SUBMITTED BY, G.BHAGYARAJ 65018140004 1st MSCZOOLOGY ST:STEPHEN’S COLLEGE PATHANAPURAM
- 4. MOLECULAR BIOLOGY ? ❖The branch of biology that deals with the structure and function of the macromolecules essential to life is called molecular biology.
- 6. NUCLEIC ACIDS Nucleicacids are the macromolecules, essential to all known forms of life. The term nucleic acid is the overall name for DNA and RNA. They are composed of nucleotides, which are the monomers made of three components: pentose sugar, phosphate group and nitrogenous base. If the sugar is a compound ribose, the polymer is RNA (ribonucleic acid); if the sugar is derived from ribose as deoxyribose, the polymer is DNA(deoxyribonucleic acid).
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- 9. IMPORTANCE OF DNA DNA is vital for all living beings – even plants. It is important for inheritance, coding for proteins and the genetic instruction guide for life and its processes. Chromosomes in the nucleus of a cell, contain information for inheritance of features from parents to next generation in the form of DNA during reproduction
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- 12. CENTRAL DOGMA OFMOLECULAR BIOLOGY
- 15. REPLICATION OF DNA (INTRODUCTION) The word ‘REPLICA’ means the exact copy of something. Replication of DNA is the process in which DNA makes exact copies of itself. Replication is the basis for inheritance. Fundamental process occurring in all cells for transfer of genetic information to daughter cells Each cell must replicate its DNA before division. DNA is copied during the S or synthesis phase of interphase. New cells will need identical DNA strands. Approximately 20 or more enzymes and proteins are needed during replication process.
- 17. In the late1950s, three different mechanisms were proposed for the replication of DNA – Conservative model • Both parental strands stay together after DNA replication – Semi-conservative model • The double-stranded DNA contains one parental and one daughter strand following replication – Dispersive model • Parental and daughter DNA are interspersed in both strands following replication POSSIBLE MODELS OF DNA REPLICATION
- 18. REPLICATION OF DNAIS SEMICONSERVATIVE
- 19. DIRECTIONALITY OF DNA Nucleotides in DNA backbone are bonded together with phosphodiester linkage between 3’ & 5’ carbons. DNA molecule has direction. Complimentary strands run in opposite direction.
- 20. BASIC RULES FORDNA REPLICATION The replication occurs in semi-conservative manner. Replication of DNA involves polymerisation of nucleotides by enzyme DNA polymerase. DNA polymerisation always proceeds in 5’– 3’ direction. The nucleotide sequence that is formed in the daughter DNA is complimentary to the to the base sequence in the template strand. The new two strands of the parental DNA duplex are anti- parallel to each other.
- 21. COMPONENTS INVOLVED IN DNAREPLICATION DNA polymerases- Deoxynucleotide polymerization Helicase -Processive unwinding of DNA RNA primase- Initiates synthesis of RNA primers Single-strand binding proteins-Prevent premature reannealing of dsDNA DNA ligase-Seals the single strand nick between the nascent chain and Okazaki fragments on lagging strand
- 24. MECHANISM IN DNA REPLICATION DNAmust always be protected inside the nucleus except during cell division (mitosis); it will get destroyed by enzymes in the cytoplasm. enzymes and free-nucleotides are available for replication in the nucleus.
- 25. 1.INITIATION An enzyme calledhelicase attaches to DNA and breaks the Hydrogen bonds to unwind and separate the complementary strands. This creates a replication fork.
- 26. 2.ELONGATION Another enzyme calledDNA polymerase attaches to one strand. It reads the DNA code, and attaches complementary nucleotides to the original exposed strand. After it attaches each complementary nucleotide, it proofreads for mistakes Replication is Quick: More Helicase and DNA Polymerase enzymes can attach at other sites on the strands to speed up the process. This creates the appearance of bubbles along the strand called replication bubbles.
- 28. 3.TERMINATION When complete, theresult should be two perfect copies of the original. Though 3.3 billion base pairs of the human genome can be copied in a matter of hours, few mistakes (mutations) occur. This process is semi-conservative: Each new molecule has one original strand and one new strand.
- 29. Prokaryotic DNA ReplicationEukaryotic DNA Replication Origin Prokaryotic DNA replication has a single origin. Eukaryotic DNA replication has multiple origins. Time Taken Prokaryotic DNA replication takes 40 minutes. Eukaryotic DNA replication may take up to 400 hours or more. Takes Place At Prokaryotic DNA replication occurs in the cytoplasm. Eukaryotic DNA replication occurs in the nucleus. Rate of Base Pairs Prokaryotic DNA replication has a rate of 2000 base pairs per second addition. Eukaryotic DNA replication has a rate of 100 base pairs per second. Nucleotide Prokaryotic DNA replication has 1000-2000 nucleotides long Okazaki fragments. Eukaryotic DNA replication has 100- 200 nucleotides long Okazaki fragments.