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Mrs. Stewart Biology I Honors

DNA Structure. Mrs. Stewart Biology I Honors. STANDARDS:. CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits. OBJECTIVES: (today, I will…).

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Mrs. Stewart Biology I Honors

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  1. DNA Structure Mrs. Stewart Biology I Honors

  2. STANDARDS: • CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. • CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits.

  3. OBJECTIVES: (today, I will…) • Evaluate the structure of nucleic acids • Determine how genetic information is “coded” in nucleic acids • Create complementary DNA strands using Chargaff’s rule

  4. Nucleic Acids • Macromolecules containing : • Carbon • Hydrogen • Oxygen • Nitrogen • Phosphorus • Function: Store and transmit genetic/hereditary information

  5. Two types of Nucleic Acids • DNA • RNA

  6. DNA Stands for: Deoxyribonucleic Acid

  7. DNA Structure • DNA is made up of two strands that are arranged into a twisted, ladder-like structure called a Double Helix. • A strand of DNA is made up of millions of tiny subunits called Nucleotides. • Each nucleotide consists of 3 parts: • Phosphate group • sugar • Nitrogenous base

  8. Nucleotides Phosphate Nitrogenous Base Pentose Sugar

  9. DNA sugar • The 5 carbon sugar for DNA is Deoxyribose • That is where the name (Deoxyribo)nucleic acid comes from

  10. 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.

  11. 4 different Nitrogen bases A T C Adenine Thymine G Guanine Cytosine

  12. Purines A Adenine G Guanine

  13. Pyrimidines T C Thymine Cytosine

  14. Chargaff’s rule • Erwin Chargaff observed that the percentage of adenine equals the percentage of thymine, and the percentage of cytosine equals the percentage of guanine. • Example: in one strand of DNA the following amounts may be found: • 15% Adenine • 15% Thymine • 35% Cytosine • 35% Guanine

  15. Complementary base pairing: • Each base will only bond with one other specific base. (Chargaff’s rule) • Adenine (A) • Thymine (T) • Cytosine (C) • Guanine (G) Form a base pair. Form a base pair.

  16. 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.

  17. A T A A A T T T C C C G G G

  18. Practice: • Complete the complementary DNA strand for the following sequence: • G T A A C T C C T • C A T A G A G G A • C T C C T A AA C • G A G G A T TT G • T A G A A T G C C • A T C T T A C G G

  19. 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 (sets of 3) 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

  20. 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.

  21. DNA Gene Protein Trait

  22. Your Task • Draw a flow chart to show how to get from:

  23. DNA Replication Mrs. Stewart Biology I Honors

  24. STANDARDS: • CLE 3210.4.1 Investigate how genetic information is encoded in nucleic acids. • CLE 3210.4.2 Describe the relationships among genes, chromosomes, proteins, and hereditary traits.

  25. OBJECTIVES: (today, I will…) • Evaluate the structure of DNA and the need for replication • Create complementary DNA strands to simulate replication

  26. DNA Double Helix • Made of 2strands of nucleotides • These strands are joined together with the pairing of the Nitrogen bases • (A, T, C, G) • The bases are joined by Hydrogenbonds

  27. Think – Pair - Share • Look at the picture and try to figure out what “antiparallel” means. • Did you notice that the strands of DNA run in “opposite directions”?

  28. 5’ and 3’ ends of DNA • Refers to the orientation of the carbon atoms on the deoxyribose • Strands run in opposite directions • One strand is “upside down”

  29. Think – pair - share • Why does DNA need to replicate itself?

  30. DNA Replication • DNA makes an exact copy of itself • Occurs during the S stage of interphase

  31. Semi-conservative • Each strand of the double helix will serve as a templatefor the new strands that will form • End result is two complete DNA double helixes – each containing one strand from the original molecule and one newly made complementary strand

  32. Helicase • Enzyme that “unzips” the DNA double helix by breaking the Hydrogen bonds between the bases to separate the strands in preparation for replication • Creates a “replication fork”

  33. DNA Polymerase • Uses “free-floating” nucleotides in the nucleus to build the complementary strand of DNA

  34. 5‘ to 3‘ direction • The new DNA strands need to form in the 5 prime to 3 prime direction. • Leading strand: forms continuously because it is forming in the 5’ to 3’ direction • Laggingstrand: forms in short segments called Okazaki fragments, so that it can also form in the 5’ to 3’ direction

  35. http://youtu.be/zdDkiRw1PdU

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