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Quiz. Mitosis and Meiosis. Check Out The New Clickers!. So cool, right? Please treat them with care! These are school property Must be returned at the end of class They are numbered, if yours goes missing, you will be held responsible Replacement cost for one clicker is $60!.

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  1. Quiz Mitosis and Meiosis

  2. Check Out The New Clickers! • So cool, right? • Please treat them with care! • These are school property • Must be returned at the end of class • They are numbered, if yours goes missing, you will be held responsible • Replacement cost for one clicker is $60!

  3. How they work Enter your answer Clear your answer Use Number/Letter Pad to Enter Answer Turn on/off

  4. How do you feel about using clickers in the classroom? • VERY COOL!! • I’m open to using them • Whatever • Waste of time [Default] [MC Any] [MC All]

  5. Clickers are cool! • True • False Try changing your answer this time. Press 1 for True and Press 2 for False. Now Press the Back Key to erase your answer. Re-enter your answer. Your clicker # should blink yellow and then turn blue again.

  6. The DNA and RNA Story Dr. Katherine Harris

  7. Chapter 12 DNA DNA Structure and contents Replication Mutation

  8. 12.3 The Structure of DNA • Rosalind Franklin’s work in 1953 using X-ray diffraction revealed that DNA had a regular structure that was shaped like a corkscrew, or helix • Francis Crick and James Watson elaborated on the discoveries of Franklin and Chargaff and deduced that the structure of DNA was a double helix • two strands of DNA bound together by hydrogen bonds between the bases • because a purine of one strand binds to a pyrimidine on the other strand to form a base pair, the molecule keeps a constant thickness

  9. Figure 12.4 The DNA double helix

  10. 12.3 Discovering the Structure of DNA • Nucleotides differ with regards to their bases • large bases (purines) with double-ring structure • either adenine (A) or guanine (G) • small bases (pyrimidines) with single rings • either cytosine (C) or thymine (T) • Edwin Chargaff noted that DNA molecules always had equal amounts of purines and pyrimidines • Chargaff’s rule suggested that DNA had a regular structure • the amount of A always equaled the amount of T • the amount of C always equaled the amount of G

  11. Deoxynucleic Acid (DNA) • Made of nucleotides. • Nucleotides have three parts: • sugar, base, phosphate. • Nucleotides connected via the sugar phosphate backbone. • DNA is double stranded. • DNA forms a double helix. • A pairs with T and G pairs with C.

  12. Figure 12.3 The four nucleotide subunits that make up DNA A bonds with T G bonds with C Purines Pyrimidines

  13. Thymine bonds with… • Guanine • Cytosine • Adenine • Uracil [Default] [MC Any] [MC All]

  14. DNA Function • DNA stores genetic information. The double helix

  15. Problems cells face • Cells need to store information in a safe place and still be able to access that information in a controlled manner. • Cells need to copy genetic information with accuracy. • Cells need to package genetic information in a small space. • Cells need to sort genetic information during cell replication.

  16. DNA Replication • Copy information. • DNA polymerase, nucleotides. • ORI • Template Strand. • Unwinding proteins. • Proofreading capacity.

  17. DNA Replication http://www.youtube.com/watch?v=4jtmOZaIvS0

  18. Prokaryotic Replication The 2 replication forks move in opposite directions on a circular chromosome.

  19. Eukaryotic Replication: Formation of Bubbles Animation Bi-directional growth of the replication fork causes the formation of bubbles in the DNA. Near the end of replication, the bubbles fuse, resolving the 2 molecules of DNA.

  20. 12.4 How the DNA Molecule Copies Itself • The two strands of DNA that form the double helix DNA molecule are complementary to each other • each chain is essentially a mirror image of the other • this complementarily makes it possible for DNA to copy itself in preparation for cell division

  21. Sequence of Events • Two strands of DNA unwind and expose their bases. • DNA Polymerase comes in and adds nucleotides which are complimentary to the template strand. • End result is 2 DNA molecules, each with an old strand and a new strand • Semi-conservative replication.

  22. Semiconservative replication produces 2 new molecules of DNA, one with 2 old strands and one with 2 new strands. • True • False

  23. Figure 12.7 How nucleotides are added in DNA replication

  24. 12.4 How the DNA Molecule Copies Itself The process of DNA replication involves several enzymes (in the order of the process) • Helicase • unwinds the DNA to expose the templates • this creates a replication fork • DNA Primase • Adds primer that allows nucleotides to be added. Like a primer before paint coat, nucleotides cannot be added without it. • DNA Polymerase • adds the correct complementary nucleotide to the growing daughter strand • but can only add nucleotides to the 3´ end of an existing strand • DNA Ligase • seals fragments of DNA together, removes primer and adds nucleotides in it’s place.

  25. 12.4 How the DNA Molecule Copies Itself • Leading Stand versus Lagging Strand • using one template, DNA polymerase adds nucleotides in a continuous fashion; this new daughter strand is called the leading strand • because the other template is a mirror image, directionality becomes a problem because DNA polymerase can build a new strand in one direction only so the second strand is made in segments and is called the lagging strand. • After replication of segments they are joined together by DNA ligase

  26. Figure 12.8 Building the leading and lagging strands http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

  27. Which of the following enzymes is responsible for unwinding the DNA during DNA Replication? • Helicase • DNA Polymerase • DNA Ligase • DNA Primase [Default] [MC Any] [MC All]

  28. Which of the following enzymes is responsible for sealing fragments of DNA together? • Helicase • DNA Primase • DNA Polymerase • DNA Ligase [Default] [MC Any] [MC All]

  29. 12.5 Mutation • There are two general ways in which the genetic message encoded in DNA can be altered • Mutation • results from errors in replication • can involve changes, additions, or deletions to nucleotides • Recombination • causes change in the position of all or part of a gene

  30. 12.5 Mutation • Mutations can alter the genetic message and affect protein synthesis (gene expression) • because most mutations occur randomly in a cell’s DNA, most mutations are detrimental • the effect of a mutation depends on the identity of the cell where it occurs • mutations in reproductive cells • these mutations will be passed to future generations • they are important for evolutionary change • mutations in somatic cells • not passed to future generations but passed to all other somatic cells derived from it

  31. 12.5 Mutation • Some mutations alter the sequence of DNA nucleotides • base substitution changes the identity of a base or bases – Just changes base or a few bases at 1 location • insertion adds a base or bases – Frameshift Mutation!! • deletion removes a base or bases – Frameshift Mutation!! • Frameshiftmutation – throws off reading frame • Proteins are read in bases of 3’s called CODONS (next chapter) • these are extremely detrimental because every amino acid from that point on will be different.

  32. Figure 12.11 Base substitution mutation

  33. Frameshift Mutation

  34. 12.5 Mutation • Some mutations affect how a genetic message is organized • transposition occurs when individual genes move from one place in the genome to another • sometimes entire regions of chromosomes may change their relative location or undergo duplication • this is called chromosomal rearrangement

  35. Table 12.1 Some Categories of Mutation

  36. 12.5 Mutation • All evolutionary change begins with alterations in the genetic message • mutation and recombination provide the raw materials for evolution • Chemicals or radiation that cause mutation are called mutagens • for example, chemicals in cigarette smoke and UV light can cause cancer

  37. Base substitution mutations typically cause the most severe damage to protein structure. • True • False

  38. Summary • DNA = double stranded nucleic acid which stores genetic information. • Mutations in DNA = Nonfunctional proteins. Frameshift mutations cause severe problems. • Semi-conservative replication of DNA.

  39. Chapter 13 How Genes Work Transcription/Translation

  40. 13.1 Transcription • The information contained in DNA is stored in blocks called genes • the genes code for proteins • the proteins determine what a cell will be like • The DNA stores this information safely in the nucleus where it never leaves • instructions are copied from the DNA into messages comprised of RNA • these messages are sent out into the cell to direct the assembly of proteins

  41. 13.1 Transcription • Proteins are transcribed from DNA to RNA • RNA is the same as DNA except that the sugars in RNA have an extra oxygen and T is replaced by another pyrimidine called uracil (U) • The cell uses three kinds of RNA • messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)

  42. RNA Structure • Composed of nucleotides. • Sugar, base, phosphate group. • Ribose sugar. • A, G, C, and Uracil (instead of Thymine). • RNA is single stranded. • A pairs with U, G pairs with C.

  43. RNA Function • RNA transfers information. • Three kinds, messenger (mRNA), transfer (tRNA), and ribosomal (rRNA). • mRNA copies information from DNA and takes it to the cytoplasm. • rRNA is part of the protein workbench. • tRNA carries amino acids to the protein workbench.

  44. 13.3 Architecture of the Gene • In eukaryotes, genes are fragmented • They are composed of • Exons – Sequences that code for amino acids • Introns – Sequences that don’t

  45. Fig. 13.7 Processing eukaryotic mRNA Protect from degradation and facilitate translation

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