DNA Replication: The Size, Structure, and Basics of DNA

1. DNA& Replication

2. The Size of DNA... If the DNA of one cell is stretched out, it makes a 7 ft. long string There are about 5 trillion cells in the human body If you connected all the DNA together, it would be long enough that it would take light over 10 hours to travel its length (ruptured bacteria) This is a whole lot of information

3. The Basics of DNA

4. DNA and Heredity… • Rosalind Franklin’s research was used in the discovery of DNA structure • Francis Crick & James Watson developed the first model of DNA • Watson & Crick concluded that all living cells contain DNA

5. Prokaryotes • Genetic material is a single loop of DNA • Located in the cytoplasm • Eukaryotes • Genetic material in the form of a chromosome • Located in the nucleus

8. Review the Cell… • Cells contain the nucleus • The nucleus is the “brains” of the cell • Chromatin – DNA tightly wrapped around proteins (histones) • Chromatinsupercoils to form chromosome • Chromosome visible during mitosis

9. Review the Cell… • Chromosomes are found inside the nucleus • Chromosomes contain genes • Genes are made up of DNA

10. DNA Structure • DNA is a Double Helix - like a twisted rubber ladder made from three main components (like legos) • Sides of the ladder are composed of alternating sugar and phosphate pieces • Each “rung” of the ladder is made up of two complementary bases • A bound to T • C bound to G • DNA is put together in chunks called NUCLEOTIDES • Each nucleotide has a sugar, PO43- and base

11. Nucleotides 5’ • A nucleotide is held together with strong molecular bonds • Oxygens provide the “hooks” necessary to bind to other NTP’s • We identify where these Oxygens are by labeling the carbons of the deoxyribose sugar 1’ 4’ 3’ 2’ (see, no oxygen at 2’…)

12. DNA Strand • Each of the components of the nucleotide binds to another nucleotide to form a single DNA strand • Since Oxygen easily forms two strong bonds, the phosphate and sugars both bind most strongly • The Hydrogens on the base bind less strongly with an Oxygen or Nitrogen from another base to bind one strand to another

14. ds DNA Helix • Finally we have the characteristics of double stranded DNA • STRONG bonds between the deoxyribose sugars and phosphates • WEAK bonds between the Hydrogen and Oxygen or Nitrogen (weaker between A and T than C and G) • Twisting of the two anti-parallel strands to form a double helix • Heat it up, which bonds break first?...

15. The Replicator • We start with some ds DNA • Replication= The copying of DNA prior to the cell undergoing division • It occurs at multiple sites along the DNA strand simultaneously • DNA strands are complementary- that is each strand can be used to make the other strand.

16. Replication #1 • DNA Helicase comes on the scene binds and • UNWINDS the DNA upstream • Then UNZIPS the hydrogen bonds between the base pairs This site is known as the replication bubble • DNA single-stranded binding proteins stabilize the single strand structure. • The sites on DNA where separation and replication occur are called replication forks. • Replication takes place in both directions until each chromosomes is completely copied. In a 5’→ 3’ direction.

17. Replication #1 • There are two replicating strands the leading strand and the lagging strand. The leading strand moves in a forward motion. The lagging strand move in a backwards motion. • The lagging strand is made up of Okazaki fragments which replicate short pieces of DNA at a time.

18. Replication #2 • DNA polymerase joins individual nucleotides to produce a DNA molecule, which is a polymer. • Complementary Bases begin adding into both sides of the ds DNA • A binds with T, C binds with G (no other possibility because of the shape of the bases!) • The final job of the Polymerase is to Proofread the NTP’s after they are added (back on the 5’ end) and to clip out any that are incorrectly paired

19. Replication #3 • Primase is an enzyme that helps start DNA replication in an Okazaki fragment. • DNA ligaseremoves the gaps that are in place due mainly to the use of primase in the lagging strand. • Finally you have 2 identical copies of double stranded DNA • The original strand serves as a template for the new strand • The resulting DNA molecules are made up of one parent (original) strand and one daughter (new) strand

21. DNA Structure and Replication

22. YouTube - DNA Transcription and Protein Assembly YouTube - DNA Replication YouTube - "The Gene Scene" YouTube - BioRap (DNA Replication and Protein Synthesis with a Beat)

23. Review Questions

24. Which of the following determines the traits of an organism? A cell nucleus B chromosomes C DNA D eggs

25. Which of the following determines the traits of an organism? A is incorrect because the nucleus does not determine traits but contains information that does. B is also incorrect because chromosomes do not determine traits but contain information that does.

26. Which of the following determines the traits of an organism? C is correct because DNA is the genetic information, found in the nucleus, that determines the traits of an organism. D is incorrect because eggs are a cell that contain genetic material that will be used to determine traits, but does not determine an organism's traits itself.

27. DNA molecules separate into single strands, which are then used to construct two identical strands of DNA. This process ensures that the — A cytoplasm is in equilibrium B mitochondria are genetically identical to the chloroplasts C parent cells use little ATP D daughter cells are genetically identical to the parent cells

28. DNA molecules separate into single strands, which are then used to construct two identical strands of DNA. This process ensures that the — A is incorrect because cytoplasm is not part of DNA molecules; rather, cytoplasm is the fluid-like substance that fills a cell. B is incorrect because mitochondria are not identical to chloroplasts; further, animal cells do not have chloroplasts, but do replicate DNA.

29. DNA molecules separate into single strands, which are then used to construct two identical strands of DNA. This process ensures that the — C is incorrect because ATP is a high energy molecule needed to provide energy for normal cellular function and is not part of DNA. D is correct because by producing identical strands of DNA, it ensures that the daughter cells are genetically identical to the parent cell.

30. The nucleus is the part of the cell that  A provides structure and support. B supplies energy to the other organelles. C changes sunlight into carbohydrates. D contains genetic information about the organism.

31. The nucleus is the part of the cell that  A is incorrect because structure and support is provided by cell membranes and cell walls. B is incorrect because mitochondria are the parts of the cell that provide energy.

32. The nucleus is the part of the cell that  C is incorrect because chloroplasts are the organelles that carry on photosynthesis. D is correct because the nucleus contains chromosomes that are made up of genes that contain DNA which is the genetic information about an organism.

33. Which of the following is not a part of DNA? A adenine B citric acid C deoxyribose D phosphate

34. Which of the following is not a part of DNA? A is incorrect because adenine is one of the bases that make up DNA. B is correct because citric acid is not part of DNA. C is incorrect because deoxyribose is sugar which is part of DNA D is incorrect because phosphate is a part of DNA.