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DNA

DNA. YUSRON SUGIARTO, STP, MP, MSc. The Structure of DNA . The Structure of DNA . DNA is wrapped tightly around histones and coiled tightly to form chromosomes . DNA. DNA is often called the blueprint of life .

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DNA

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  1. DNA YUSRON SUGIARTO, STP, MP, MSc

  2. The Structure of DNA

  3. The Structure of DNA

  4. DNA is wrapped tightly around histones and coiled tightly to form chromosomes

  5. DNA • DNAis often called the blueprint of life. • In simple terms, DNA contains the instructions for making proteins within the cell.

  6. The earth is 150 billion m or 93 million miles from the sun. DNA by the numbers • Each cell has about 2 m of DNA. • The average human has 75 trillion cells. • The average human has enough DNA to go from the earth to the sun more than 400 times. • DNA has a diameter of only 0.000000002 m.

  7. Why do we study DNA? We study DNA for many reasons, e.g., • its central importance to all life on Earth, • medical benefits such as cures for diseases, • better food crops.

  8. Our genes are on our chromosomes. Chromosomes are made up of a chemical called DNA. Chromosomes and DNA

  9. DNA Structure • DNA consists of two molecules that are arranged into a ladder-like structure called a Double Helix. • A molecule of DNA is made up of millions of tiny subunits called Nucleotides. • Each nucleotide consists of: • Phosphate group • Pentose sugar • Nitrogenous base

  10. One Strand of DNA phosphate • The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts. • The teeth are nitrogenousbases. deoxyribose bases

  11. Nucleotides Phosphate Nitrogenous Base Pentose Sugar

  12. Nucleotides • The phosphate and sugar form the backbone of the DNA molecule, whereas the bases form the “rungs”. • There are four types of nitrogenous bases.

  13. Nucleotides A T C Adenine Thymine G Guanine Cytosine

  14. Nucleotides • Each base will only bond with one other specific base. • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G) Form a base pair. Form a base pair.

  15. Four nitrogenous bases • Cytosine C • Thymine T • Adenine A • Guanine G DNA has four different bases:

  16. N N C N C C C N N C Two Kinds of Bases in DNA • Pyrimidines are single ring bases. • Purines are double ring bases. N N C O C C N C

  17. One Strand of DNA phosphate • The backbone of the molecule is alternating phosphate and deoxyribose, a sugar, parts. • The teeth are nitrogenousbases. deoxyribose bases

  18. N O N N C C O C C O C C C N C N C thymine cytosine Thymine and Cytosine are pyrimidines • Thymine and cytosine each have one ring of carbon and nitrogen atoms.

  19. O N N N C C N C C C C N N N C N C C Guanine Adenine C N N Adenine and Guanine are purines • Adenine and guanine each have two rings of carbon and nitrogen atoms.

  20. Two Stranded DNA • Remember, DNA has two strands that fit together something like a zipper. • The teeth are the nitrogenous bases but why do they stick together?

  21. N O N C N C O C C N C C N N C N C C N Hydrogen Bonds • The bases attract each other because of hydrogen bonds. • Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA. • (The bonds between cytosine and guanine are shown here.)

  22. O N C O C C C N C N N C C C N N C C N Hydrogen Bonds, cont. • When making hydrogen bonds, cytosine always pairs up with guanine, • And adenine always pairs up with thymine. • (Adenine and thymine are shown here.)

  23. Important: Adenine and Thymine always join together A T Cytosine and Guanine always join together C G

  24. DNA Structure • Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

  25. A T A A A T T T C C C G G G

  26. DNA Structure • To crack the genetic code found in DNA we need to look at the sequence of bases. • The bases are arranged in triplets called codons. A G G - C T C - A A G - T C C - T A G T C C - G A G - T T C - A G G - A T C

  27. DNA Structure • A gene is a section of DNA that codes for a protein. • Each unique gene has a unique sequence of bases. • This unique sequence of bases will code for the production of a unique protein. • It is these proteins and combination of proteins that give us a unique phenotype.

  28. DNA

  29. DNA Replication Models

  30. lagging strand Replication fork Replication fork Leading strand

  31. DNA Replication

  32. DNA Replication • DNA must be copied • The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing: A-T, G-C • Each strand of the original DNA serves as a template for the new strand

  33. DNA Template Parental DNA New DNA DNA Replication • Semiconservative Model: Watson and Crick showed: the two strands of theseparate, and each functions as a for synthesis of a new complementary strand. .

  34. DNA Replication • Complementary base pairs form new strands.

  35. DNA

  36. Replication Quiz 1. Why is replication necessary? 2. When does replication occur? 3. Describe how replication works. • Use the complementary rule to create the complementary strand: A---? G---? C---? T---? A---? G---? A---? G---? C---? A---? G---? T---?

  37. Replication Quiz 1. Why is replication necessary? So both new cells will have the correct DNA 2. When does replication occur? During interphase (S phase). 3. Describe how replication works. Enzymes unzip DNA and complementary nucleotides join each original strand. 4. Use the complementary rule to create the complementary strand: A---T G---C C---G T---A A---T G---C A---T G---C C---G A---T G---C T---A

  38. Satutimbesar yang terdiridarienzimdan protein lain menjadipelaksanareplikasi DNA • Protein-protein yang berperan dalam replikasi DNA • Helikase: enzim yang berfungsi membuka heliks ganda di cabang replikasi, memisahkan untai lama. • Protein pengikat untai tunggal: menjaga agar untai-untai tetap terpisah selama bertindak sebagai cetakan dalam sintesis untai-untai komplementer yang baru. • Primase: membentuk primer

  39. Satutimbesar yang terdiridarienzimdan protein lain menjadipelaksanareplikasi DNA • Protein-protein yang berperan dalam replikasi DNA • DNA polimerase: pemanjangan untai DNA baru • Ligase: menggabungkan rantai DNA

  40. Enzymology of DNA replication DNA strand separation Helicases: unwind double strand DNA Single-strand DNA binding proteins (SSBs): participate in DNA strand separation but do not catalyze the strand separation process. They bind to single strand DNA as soon as it forms and coat it so that it cannot anneal to reform a double helix. Topoisomerases: introduce transient single or double stranded breaks into DNA and thereby allow it to change its form, or topology.

  41. DNA polymerases 3’-5’ exo Three DNA polymerases (I, II, III) DNA polymerase I (102 KD): has three different enzymatic activities DNA polymerase 3’-5’ exonuclease activity 5’-3’ exonulcease activity (proof reading to increase fidelity) (remove RNA primers or damage DNA on its path)

  42. Pol III holoenzyme 10 subunits Move at an extremely rapid rate (1000 nts/second) Proof reading

  43. Eukaryotes have multiple DNA polymerases

  44. THANK YOU YUSRON SUGIARTO, STP, MP, MSc

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