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DNA Replication

DNA Replication. 1 st The DNA helices unwind from the nucleosome Fig 3.29. Cont. 2 nd DNA Helicase unwinds the double helix. separates the DNA molecule into two complementary nucleotide chains. Cont. 3 rd Remember base pairing complementarity. . A – T C – G

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DNA Replication

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  1. DNA Replication • 1st The DNA helices unwind from the nucleosome Fig 3.29

  2. Cont. 2nd DNA Helicase unwinds the double helix

  3. separates the DNA molecule into two complementary nucleotide chains

  4. Cont. • 3rd Remember base pairing complementarity.

  5. A – T • C – G • In RNA, T replaced by U

  6. Process driven by DNA polymerase, which links the DNA nucleotides together and works in only one direction

  7. Leading strand follows replicating fork Lagging strand constructed in segments in the opposite direction Within the replication fork

  8. 4th • Short segments of DNA are spliced together by DNA ligase.

  9. Result: 2 molecules are formed from and identical to the original DNA helix.

  10. The intention is for the newly formed DNA to be perfect, nucleotide for nucleotide.

  11. Cont. • The newly formed DNA molecules consist of 1 old and 1 new strand.

  12. This mechanism is referred to as semiconservative replication

  13. Protein Synthesis • A gene is a segment of DNA that carries instructions for one polypeptide chain

  14. Three bases, triplet on DNA, translate to a codon on mRNA, and to one amino acid in translation.

  15. Based on the genetic code • A biological language universal to all life on earth

  16. Role of RNA • 1. Transfer RNA (tRNA) • 2. Messenger RNA (mRNA) • 3. Ribosomal RNA (rRNA)

  17. Transcription and Translation Goal is to make proteins

  18. Transcription

  19. 1st transcription factor binds to a special DNA site adjacent to the promoter(start sequence) region.

  20. 2nd this (promoter region) shows RNA polymerase where to bind.

  21. RNA pol transcribes creating a complementary mRNA strand

  22. mRNA is edited • Introns or nonsense regions are removed. • What purpose?

  23. Remaining exons sections are spliced together and will be translated.

  24. Translation

  25. Translation • The language of nucleic acids are translated into the language of amino acids.

  26. 1st • mRNA leaves nucleus and attaches to ribosome.

  27. 2nd • tRNA transports amino acids to the mRNA strand.

  28. tRNA recognizes codons calling for its amino acid by base paring

  29. 3rd • Ribosomes move along the mRNA strand as each codon is read

  30. 4th • As each amino acid is bound to the next by a ___________ bond, its tRNA is released

  31. 5th • The polypeptide is released when the stop codon is read

  32. Animation of protein synthesis

  33. Developmental Aspects of Cells • The development of specific and distinctive features in cells is called cell differentiation

  34. Brain development

  35. Embryonic stem cells

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