DNA structure and replication
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Structure of DNA
Purine and pyrimidine nucleotides are the building blocks of DNA. Adenine specifically binds to thymine with 2 hydrogen bonds and cytosine specifically binds to guanine with three hydrogen bonds. Hydrogen bond is a type of attractive intermolecular force that exists between two partial electric charges of opposite polarity. Two strands of DNA are anti parallel with major and minor grooves.
DNA replication
The process of making an identical copy of a section of duplex DNA, using existing DNA as template for the synthesis of new DNA strands. DNA undergoes semi conservative nature of replication. There are three steps in the replication process: Initiation, elongation and termination. Initiation always begins at the origins of replication, it is bidirectional with most genomes and priming is with RNA. Elongation has three steps: unwinding of DNA, relieving of torsional stress and polymerization of poly nucleotide chain. One strand of DNA is made continuously while the other strand is synthesized in fragments.
Functions and structures of DNA replication enzymes
Many enzymes are involved in DNA replication such as topoisomerase, helicase, primase, DNA polymerase and ligase. Topoisomerases relax the super coiling of DNA, helicases unwind double strand of DNA, primases synthesize a primer, DNA polymerases add and read proof new bases and ligases link the added bases.
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| "Title" Tutorial Summary : |
Purine and pyrimidine nucleotides are the building blocks of DNA. Adenine specifically binds to thymine with 2 hydrogen bonds and cytosine specifically binds to guanine with three hydrogen bonds. Two strands of DNA are anti parallel with major and minor grooves. DNA undergoes semi conservative nature of replication. There are three steps in the replication process: Initiation, elongation and termination. Many enzymes are involved in DNA replication such as topoisomerase, helicase, primase, DNA polymerase and ligase.
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| Tutorial Features: |
- Concept map which shows the central role of DNA.
- Animated structures of double helical anti parallel DNA strands.
- DNA replication process explained with schematic representations.
- Enzymes of DNA replication are listed with their functions.
- Mechanism of the enzyme actions are depicted with animated diagrams.
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| "Title" Topic List: |
Structure of DNA
- Building blocks of DNA
- Hydrogen bonds. Watson-Crick rules
- Anti parallel double helix
- Helical structure
DNA replication
- Definition
- Semi conservative nature of DNA replication
- Initiation
- Elongation
- Termination
Functions and structures of DNA replication enzymes
- Topoisomerase and its mechanism
- Helicase and its mechanism
- Primase
- DNA polymerase
- DNA Ligase and its mechanism
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