Dna replication 2final

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Dna replication 2final

  1. 1. DNA REPLICATION MISS SOFIA PAZ
  2. 2. WHEN A CELL DIVIDES A COMPLETE SET OF GENETIC INSTRUCTIONS IS GENERATED FOR EACH NEW CELL. Template mechanism Based on the specific pairing rules of complementary bases. REPLICATION: The process of copying the DNA molecule What is to replicate something??? HOW does cells replicate DNA??? By a TEMPLATE MECHANISM!! (photo negative)
  3. 3. REPLICATION • DNA is copied semi-conservatively. This means that each old strand of DNA pairs with a strand made from new nucleotides. • Replication starts at a fixed point and is bidirectional (replicates in both directions).
  4. 4. Replication takes place in the nucleus Enzyme separates the strands Polymerase joins a complementary base to the new strand.
  5. 5. The TEMPLATE FOR Ther leading strand: Replication fork moves from 3’ to 5’
  6. 6. STEP EVENTS Key words Step1 BREAKING HYDROGEN BONDS between bases of the two antiparallel strands with Helicase Enzyme forming the Replication Fork Origin of replication Helicase Hyodrogen bonds Replication Fork Step2 BINDING OF DNA PRIMASE in the the initiation point of the 3'-5' parent chain DNA Primase attract RNA nucleotides which bind to the DNA nucleotides of the 3'-5‘ RNA nucleotides are the primers (starters) for the binding of DNA nucleotides Step3 THE ELONGATION PROCESS( Leading strand 5'-3' template different process thanLagging strand3'-5' template) A)Leading Strand (5'-3' Template)DNA Polymerase delta can "read" the template and continuously adds nucleotides Leading strand (5'-3' template) Lagging strand (3'-5' template) DNA Polymerase delta Step3 B)Lagging Strand (3'-5'Template): cannot be "read" by DNA Polymerase sigma. more RNA Primers. DNA polymerase epsilon reads the template and lengthens the bursts. The gap between two RNA primers is called "Okazaki Fragments" Lagging strand RNA primers Okazaki Fragments DNA Polymerase epsilon Step4 TERMINATION DNA Polymerase reaches to an end of the strands DNA Polymerase Step5 MECHANISM OF REPAIR It fixes possible errors caused Nucleases
  7. 7. STEPS Helicase is the enzyme that splits the two strands The unwounding of the two strands is the starting point The initiation point where the splitting starts is called "origin of replication" The structure that is created is known 1. FIRST STEP The first step of DNA Replication is BREAKING HYDROGEN BONDS between bases of the two antiparallel strands The splitting happens in places of the chains which are rich in A-T (because there are only two bonds between Adenine and Key Words: Origin of replication Helicase Hyodrogen bonds Replication Fork
  8. 8. DNA primase can attract RNA nucleotides which bind to the DNA nucleotides of the 3'-5' strand due to the hydrogen bonds between the bases RNA NUCLEOTIDES ARE THE PRIMERS (STARTERS) for the binding of DNA nucleotides 2. SECOND STEP Is THE BINDING OF DNA PRIMASE in the the initiation point of the 3'-5' parent chain.
  9. 9. Leading Strand : DNA Polymerase delta can "read" the template and continuously adds nucleotides (complementary to the nucleotides of the template, for example adenine opposite to thymine etc) 3. THIRD STEP IS THE ELONGATION PROCESS Different For The 5'-3' And 3'-5' Template KEY WORDS: Leading strand (5'-3' template) Lagging strand (3'-5' template) DNA Polymerase delta and
  10. 10. The TEMPLATE FOR Ther leading strand: Replication fork moves from 3’ to 5’
  11. 11. -3'-5' TEMPLATE CANNOT BE "READ" BY DNA POLYMERASE DELTA. -IN THE LAGGING STRAND DNA PRIMASE ADDS MORE RNA PRIMERS. DNA POLYMERASE EPSILON READS THE TEMPLATE AND LENGTHENS THE BURSTS. THE GAP BETWEEN TWO RNA PRIMERS IS CALLED "OKAZAKI FRAGMENTS". -THE RNA PRIMERS ARE NECESSARY FOR DNA POLYMERASE EPSILON TO BIND NUCLEOTIDES TO THE 3' END OF THEM. -THE DAUGHTER STRAND IS ELONGATED WITH THE BINDING OF MORE DNA NUCLEOTIDES. 3. THIRD STEP ELONGATION PROCESS Different For The 5'-3' And 3'-5' Template KEY WORDS: Leading strand (5'-3' template) Lagging strand (3'-5' template)
  12. 12. DNA POLYMERASE REACHES TO AN END OF THE STRANDS EUKARYOTES LINEAR CHROMOSOMES, DNA REPLICATION IS UNABLE TO REACH THE VERY END OF THE CHROMOSOMES ENDS AT THE TELOMERE REGION OF REPETITIVE DNA AT THE END → SHORTENS THE TELOMERE OF DAUGHTER DNA STRAND. SOMATIC CELLS, NORMAL PROCESS, CAN ONLY DIVIDE A CERTAIN NUMBER OF TIMES GERM CELL LINE(PASSES DNA TO THE NEXT GENERATION) TELOMERASE EXTENDS THE REPETITIVE SEQUENCES OF THE TELOMERE REGION TO PREVENT DEGRADATION 4. FOURTH STEP TERMINATION KEY WORDS: DNA Polymerase Linear chromosomes Telomere region Telomerase
  13. 13. IT FIXES POSSIBLE ERRORS CAUSED DURING THE REPLICATION NUCLEASES REMOVE THE WRONG NUCLEOTIDES AND THE DNA POLYMERASE FILLS THE GAPS) 5. FIFTH STEP MECHANISM OF REPAIR KEY WORDS: Nucleases DNA polymerases
  14. 14. http://www.youtube.com/watch?v=8kK2zwjRV0M http://www.youtube.com/watch?v=dIZpb93NYlw http://www.youtube.com/watch?v=2iVltkYy0jg http://www.youtube.com/watch?v=gW3qZF9cLIA http://www.youtube.com/watch?v=1L8Xb6j7A4w

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