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DNA Replication, Transcription and Translation

DNA Replication, Transcription and Translation. DNA- stands for d eoxyribo n ucleic a cid DNA is a combination of nucleic acids and histones nucleic acid- polymer of nucleotides histone - protein structure. Nucleotides are made of 3 parts: Phosphate group

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DNA Replication, Transcription and Translation

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  1. DNAReplication, Transcription and Translation

  2. DNA- stands for deoxyribonucleic acid DNA is a combination of nucleic acids and histones • nucleic acid- polymer of nucleotides • histone- protein structure

  3. Nucleotides are made of 3 parts: • Phosphate group • A 5-carbon (pentose) sugar, deoxyribose • A nitrogenous base

  4. Purines The nitrogenous bases: 1. Adenine 2. Guanine 3. Thymine 4. Cytosine Pyrimidines

  5. The combination of the phosphate, sugar, and nitrogenous base makes a nucleotide

  6. Because of the four nitrogenous bases, four different nucleotides are seen in DNA The covalent and hydrogen bonding between nucleotides creates the DNA molecule

  7. DNA Molecule DNA is made of two strands of nucleotides. Together, the two strands form a “ladder” or double helix. The sugar-phosphate backbone forms the sides of the ladder

  8. Phosphates Sugars “Sides of the ladder”

  9. The two strands are identical to each other, but antiparallel (heading in opposite directions)

  10. The nitrogenous bases of the two strands forms the rungs.

  11. Hydrogen bonding between the bases holds the chains together. A - T C - G The random order of the bases down the DNA chain accounts for unlimited number of proteins made from DNA

  12. A T 2 hydrogen bonds

  13. 2 hydrogen bonds

  14. C G 3 hydrogen bonds

  15. 3 hydrogen bonds

  16. Individual nucleotides are bonded together through condensation reactions between Carbon 3 and the next phosphate group

  17. LEAVES TO FORM H2O 3’ OH OH H O P O CH2 5’ OH

  18. H 3’ H + O O 5’ O O P CH2 OH

  19. DNA Replication

  20. During interphase of the cell cycle, DNA makes an exact copy of itself. This process is DNA Replication The process involves the separation or “unzipping” of the DNA chains.

  21. Each strand of the original chain serves as a template to assemble the new complementary strand. Result is two identical DNA chains each with an original template from old DNA

  22. Replication Bubbles

  23. The process of having DNA replication with one strand being old DNA (template) and one new replicated DNA (complementary strand) is called semiconservative replication

  24. Original DNA strand Templates after “unzipping” New DNA strands attach to templates

  25. Major steps in DNA Replication:

  26. Helicase enzyme breaks hydrogen bonds between DNA strands

  27. The location where the helicase is splitting the DNA chain is the Replication Fork Replication Fork Helicase

  28. DNA is divided into two individual strands. One strand is 3’ 5’, the other is 5’ 3’. 5’ 3’ 3’ 5’

  29. DNA polymerase, an enzyme, only attaches and moves down the 3’5’ strand. It attaches new nucleotides to the exposed template in the 5’3’ direction, creating a new antiparallel strand

  30. On the 3’ 5’ strand, the DNA Polymerase follows the replication fork. This allows the 5’ 3’ strand to be made in a long continuous chain. This is the leading strand

  31. Leading strand DNA polymerase Lagging strand

  32. On the original 5’ 3’ template, DNA polymerase must operate in the opposite direction away from the replication fork. This strand is the lagging strand

  33. Leading strand DNA polymerase Lagging strand

  34. This results in DNA polymerase attaching many short segments of nucleotides away from the replication fork. These short segments are called Okazaki fragments

  35. The Okazaki fragments are connected together by an enzyme called DNA Ligase. All of the short segments are joined into one long complementary strand.

  36. After replication, DNA polymerase and other enzymes proofread the new strand for errors. If an error is not corrected, it becomes a mutation.

  37. Mutation types: 1. Substitution mutation- Incorrect nucleotide inserted AG GC AT GC

  38. 2. Insertion mutation- an extra nucleotide inserted into the sequence AT GC AT GC G

  39. 3. Deletion Mutation a nucleotide is removed or missing A GC AT GC

  40. RNA

  41. RNA stands for- ribonucleic acid Major differences between DNA and RNA: 1. Sugar in the nucleotide is ribose

  42. Deoxyribose Ribose HOCH2 HO HOCH2 HO OH H OH OH

  43. 2. RNA does not hold the nitrogenous base Thymine. Instead Uracil is used. When base pairing occurs, Uracil bond to Adenine. A-U

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