1. DNA Structure and Analysis
PowerPoint® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino
Chapter 10
DNA Structure and Analysis
Lectures by David Kass with contributions from John C. Osterman.
Copyright © 2009 Pearson Education, Inc.

2. 10.1 The Genetic Material Must Exhibit Four Characteristics
It must be able to:
replicate
store information
express information
The Cenral Dogma
allow variation by mutation

3. Section 10.2
Until 1944, Observations Favored Protein as the Genetic Material
Known that genetic material is physically transmitted from parent to offspring.
Proteins and nucleic acids were the major candidates for the genetic material.

4. 10.3 Evidence Favoring DNA as the Genetic Material Was First Obtained during the Study of Bacteria and Bacteriophages

5. Section 10.3
Griffith showed that avirulent strains of Diplococcus pneumoniae could be transformed to virulence.

6. Section 10.3
Avery, MacLeod, and McCarty (1944) demonstrated that the transforming principle was DNA and not protein.

7. Figure 10.4 Summary of Avery, MacLeod, and McCarty’s experiment, which demonstrated that DNA is the transforming principle.
Figure 10.4

8. Section 10.3
Hershey and Chase (1952) demonstrated that DNA, and not protein, enters the bacterial cell during bacteriophage infection and directs viral reproduction.

9. Figure 10.5 Reproductive cycle of a T-even bacteriophage, as known in The electron micrograph shows an E. coli cell during infection by numerous phages.
Figure 10.5

10. Figure 10.6 Summary of the Hershey–Chase experiment demonstrating that DNA, and not protein, is responsible for directing the reproduction of phage T2 during the infection of E. coli.
Figure 10.6

11. Section 10.4
Indirect and Direct Evidence Supports the Concept that DNA Is the Genetic Material in Eukaryotes
DNA is found only where the primary genetic function occurs.
Whereas protein is found throughout the cell.
This provides indirect evidence for DNA as the genetic material.

12. Section 10.4
UV light is capable of inducing mutations in the genetic material and is most mutagenic at a wavelength of 260 nm.

13. Section 10.4
Strongest direct evidence for DNA = recombinant DNA technology.

14. Section 10.6
Knowledge of Nucleic Acid Chemistry Is Essential to the Understanding of DNA Structure
Nucleotides are the building blocks of DNA.
They consist of:
a nitrogenous base
a pentose sugar
a phosphate group

15. Section 10.6 Nitrogenous bases can be purines or pyrimidines. Purines
adenine (A) and guanine (G)
Pyrimidines
cytosine (C), thymine (T), and uracil (U)

16. Section 10.6 DNA and RNA both contain A, C, and G.
Only DNA contains T.
Only RNA contains U.
RNA contains ribose as its sugar.
DNA contains deoxyribose (Figure 10.9).

17. Figure 10.9 (a) Chemical structures of the pyrimidines and purines that serve as the nitrogenous bases in RNA and DNA. The nomenclature for numbering carbon and nitrogen atoms making up the two bases is shown within the structures that appear on the left. (b) Chemical ring structures of ribose and 2-deoxyribose, which serve as the pentose sugars in RNA and DNA, respectively.Web Tutorial 10.1DNA Structure
Figure 10.9

18. Section 10.6
A nucleoside contains the nitrogenous base and the pentose sugar.
A nucleotide is a nucleoside with a phosphate group added.

19. Section 10.6
The C-5' position is the location of the phosphate group on a nucleotide.

20. Section 10.6
Nucleotides can have one, two, or three phosphate groups and are called NMPs, NDPs, and NTPs, respectively.

21. Section 10.6
Nucleotides are linked by a phosphodiester bond between the phosphate group at the C-5' position and the OH group on the C-3' position.

22. Section 10.7
Chargaff showed that the amount of A is proportional to T and the amount of C is proportional to G, but the percentage of C + G does not necessarily equal the percentage of A + T (Table 10.3).

23. Early DNA Studies
Rosalind Franklin and Maurice Wilkins studied DNA structure using X-ray scattering
X-ray diffraction photograph of the B form of purified DNA fibers. The strong arcs on the periphery show closely spaced aspects of the molecule, providing an estimate of the periodicity of nitrogenous bases, which are 3.4 Å apart. The inner cross pattern of spots shows the grosser aspect of the molecule, indicating its helical nature.
From X-ray diffraction patterns they deduced that DNA
Is long and thin
Has a uniform diameter of 2 nanometers
Is helical, and is twisted like a corkscrew
Consists of repeating subunits

24. Section 10.7 Watson and Crick proposed:
DNA is a right-handed double helix
Two strands are antiparallel and the bases are stacked on one another.
Two strands are connected by A-T and G-C base pairing
There are 10 base pairs per helix turn (Figure 10.14).

25. Figure 10. 14 (a) The DNA double helix as proposed by Watson and Crick
Figure (a) The DNA double helix as proposed by Watson and Crick. The ribbonlike strands constitute the sugar-phosphate backbones, and the horizontal rungs constitute the nitrogenous base pairs, of which there are 10 per complete turn. The major and minor grooves are apparent. The solid vertical bar represents the central axis. (b) A detailed view depicting the bases, sugars, phosphates, and hydrogen bonds of the helix. (c) A demonstration of the antiparallel nature of the helix and the horizontal stacking of the bases.
Figure 10.14

26. Figure 10-15 The right- and left-handed helical forms of DNA
Figure The right- and left-handed helical forms of DNA. Note that they are mirror images of one another.
Figure 10.15

27. Section 10.7
A-T & G-C base pairing provides complementarity of the 2 strands & chemical stability to the helix.
A-T base pairs form 2 hydrogen bonds & G-C base pairs form 3 hydrogen bonds.

28. Section 10.7
Arrangement of sugars and bases along the axis provides another stabilizing factor.

29. Alternative Forms of DNA Exist
Watson-Crick DNA model is of B-DNA, which is believed to be the biologically significant form.
A-DNA is slightly more compact than B-DNA.
C-DNA, D-DNA, and E-DNA are also right-handed forms of DNA that are less compact than B-DNA.
Z-DNA forms a left-handed double helix

30. Figure The top half of the figure shows computer-generated space-filling models of B-DNA (left), A-DNA (center), and Z-DNA (right). Below is an artist’s depiction illustrating the orientation of the base pairs of B-DNA and A-DNA. (Note that in B-DNA the base pairs are perpendicular to the helix, while they are tilted and pulled away from the helix in A-DNA.)
Figure 10.17

31. Section 10.9
The Structure of RNA Is Chemically Similar to DNA, but Single Stranded
In RNA:
the sugar ribose replaces deoxyribose of DNA
and uracil replaces thymine of DNA
Usually single-stranded

32. Section 10.9 There are 3 classes of cellular RNAs:
messenger RNA (mRNA)
the template for protein synthesis
ribosomal RNA (rRNA)
components of ribosomes for protein synthesis
transfer RNA (tRNA)
carry amino acids for protein synthesis

33. The End