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DNA

DNA. Deoxyribonucleic Acid. O.L Lesson Objectives. At the end of this lesson you should be able to Outline the simple structure of DNA – 2 strands and A,T,C, G complement Distinguish between coding and non coding structures Describe the triplet base code

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DNA

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  1. DNA Deoxyribonucleic Acid

  2. O.L Lesson Objectives At the end of this lesson you should be able to • Outline the simple structure of DNA – 2 strands and A,T,C, G complement • Distinguish between coding and non coding structures • Describe the triplet base code • Outline the structure of RNA – refer to Uracil and complement to DNA • Know the function of mRNA • Discuss the replication of DNA

  3. What is DNA • Hereditary material • Carries and passes on genetic information • It is a nucleic acid • Made up of nucleotides

  4. The DNA Double Helix • Two parallel strands • Each with a series of bases to the inside • The bases are directly opposite each other • The bases link each other in pairs • These links form the steps of the ladder

  5. The DNA Double Helix Hydrogen bond- link Parallel Strand Parallel Strand Base Base

  6. The Bases Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

  7. The Base Pair Rule • The bases can occur in any sequence along a strand of DNA • But the sequence must be complimentary to the sequence on the other strand

  8. The Base Pair Rule • Adenine can only join to Thymine A T • Guanine can only join to Cytosine G C

  9. Building DNA http://www.zerobio.com/drag_gr9/DNA/dna.htm

  10. Building DNA http://learn.genetics.utah.edu/units/basics/builddna/

  11. Learning Check • What does DNA stand for? • Name the four bases in DNA • Which base complements Adenine? • Which base compliments Guanine?

  12. Non Coding DNA • Only about 3% of DNA is composed of genes • 97% of DNA is non coding DNA or junk DNA

  13. Coding DNA • The parts of DNA that contain information to make RNA or protein • Coding DNA in genes are called exons

  14. Non Coding DNA • Do not contain critical information for the production of protein • They are now thought to play a role in gene expression • Non coding DNA within genes is called introns

  15. Learning Check Label a gene and a piece of non coding DNA in the following picture

  16. RNA Ribonucleic Acid Operates with DNA to make proteins Has Uracil instead of Thymine

  17. Differences between DNA and RNA • RNA • Single strand • Sugar is ribose • Has Uracil • Short molecule • Not self replicating • Found in nucleus and cytoplasm DNA • Double strand • Sugar is deoxyribose • Has Thymine • Very long • Self replicating • Found only in the nucleus

  18. Similarities between DNA and RNA • Both are nucleic acids • Both contain adenine, guanine and cytosine nucleotides • Operate together to produce specific proteins

  19. Learning Check • What does RNA stand for? • What three bases do DNA and RNA have in common? • What base does RNA have instead of Thymine? • Where do you find both DNA and RNA? • Where else will you find RNA?

  20. H.L Objectives At the end of this section you should know ….. DNA structure – deoxyribose sugar, sugar, phosphate and 4 named nitrogenous bases Nucleotide structure Specific Purine and Pyramidine couples – complementarybase pairs Hydrogen bonding Double helix

  21. Higher Level Nucleic Acid Structure

  22. Nucleotides • Nucleotides are carbon ring structures containing nitrogen linked to a 5-carbon sugar (a ribose) • 5-carbon sugar is either a ribose or a deoxyribose • In eukaryotic cells nucleic acids are either: Deoxyribose nucleic acids (DNA) Ribose nucleic acids (RNA)

  23. OH Base NH2 - P HO O H+ H O N N N N H Phosphate CH2 5’ O 1’ 4’ Sugar 3’ 2’ OH H OH A Nucleotide

  24. Coding and Non Coding Parts • Non coding Structures Sugar – Phosphate • Coding Structures Base Sequences

  25. Purine Bases • Adenine and Guanine Double ringed molecular structures Known as Purine Bases

  26. Pyrimidine Bases • Thymine and Cytosine single ringed structures Known as Pyrimidine bases

  27. NH2 Thymine (DNA) Uracil (RNA) CH3 Adenine N N N N N O N N NH N O O O N O O NH NH N N N O NH2 NH2 Guanine Cytosine NH2 N N Purines Pyrimidines

  28. Base Numbers Number of Purine Bases = Number of Pyrimidine Bases This led to the discovery of Base Pairing

  29. Cytosine N O O N N N N Guanine H H O N H N N N H H Base PairingGuanine And Cytosine - + + - - + Three Hydrogen Bonds

  30. H H + N - Adenine Thymine CH3 H - + N N N N N N O O N Base PairingAdenine And Thymine Two Hydrogen Bonds

  31. - + - Thymine CH3 H + + N N N N N O N O N Guanine O H N H H Base PairingGuanine And Thymine

  32. The Watson - Crick Model Of DNA - - AT - - CG - - GC - - TA - - 3.4 nm 1 nm - - - - GC TA - - CG - - AT - - - - AT - - CG - - GC - - 0.34 nm TA - - Minor groove Major groove

  33. What have you learned Can you ……………… • Outline the simple structure of DNA • Name the four bases and the base pairs in DNA • Distinguish between coding and non coding structures • Define triplet base code • Outline the structure of RNA • Name the bases in RNA and know the function of mRNA • Discuss the replication of DNA

  34. End

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