1. CHAPTER 10 Molecular Biology of the Gene
Modules 10.1 – 10.5

2. Saboteurs Inside Our Cells
The invasion and damage of cells by the herpesvirus can be compared to the actions of a saboteur intent on taking over a factory
The herpesvirus hijacks the host cell’s molecules and organelles to produce new copies of the virus

3. Viruses provided some of the earliest evidence that genes are made of DNA
Molecular biology studies how DNA serves as the molecular basis of heredity

4. 10.1 Experiments showed that DNA is the genetic material
THE STRUCTURE OF THE GENETIC MATERIAL
10.1 Experiments showed that DNA is the genetic material
The Hershey-Chase experiment showed that certain viruses reprogram host cells to produce more viruses by injecting their DNA
Head
DNA
Tail
Tail fiber
Figure 10.1A

5. The Hershey-Chase Experiment1
Mix radioactively labeled phages with bacteria. The phages infect the bacterial cells. 2
Agitate in a blender to separate phages outside the bacteria from the cells and their contents. 3
Centrifuge the mixture so bacteria form a pellet at the bottom of the test tube. 4
Measure the radioactivity in the pellet and liquid.
Radioactive protein
Empty protein shell
Radioactivity in liquid
Phage
Bacterium
Phage DNA
DNA
Batch 1 Radioactive protein
Centrifuge
Pellet
Radioactive DNA
Batch 2 Radioactive DNA
Centrifuge
Radioactivity in pellet
Figure 10.1B
Pellet

6. Phage reproductive cycle
Phage attaches to bacterial cell.
Phage injects DNA.
Phage DNA directs host cell to make more phage DNA and protein parts. New phages assemble.
Cell lyses and releases new phages.
Figure 10.1C

7. 10.2 DNA and RNA are polymers of nucleotides
DNA is a nucleic acid, made of long chains of nucleotides
Phosphate group
Nitrogenous base
Nitrogenous base (A, G, C, or T)
Sugar
Phosphate group
Nucleotide
Thymine (T)
Sugar (deoxyribose)
DNA nucleotide
Polynucleotide
Sugar-phosphate backbone
Figure 10.2A

8. DNA has four kinds of bases, A, T, C, and G
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Pyrimidines
Purines
Figure 10.2B

9. Nitrogenous base (A, G, C, or U)
RNA is also a nucleic acid
RNA has a slightly different sugar
RNA has U instead of T
Nitrogenous base (A, G, C, or U)
Phosphate group
Uracil (U)
Sugar (ribose)
Figure 10.2C, D

10. 10.3 DNA is a double-stranded helix
James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin
Figure 10.3A, B

11. The structure of DNA consists of two polynucleotide strands wrapped around each other in a double helix
1 chocolate coat,
Blind (PRA)
Figure 10.3C
Twist

12. Hydrogen bonds between bases hold the strands together
Each base pairs with a complementary partner
A pairs with T
G pairs with C

13. Partial chemical structure
Three representations of DNA
Hydrogen bond
Ribbon model
Partial chemical structure
Computer model
Figure 10.3D

14. 10.4 DNA replication depends on specific base pairing
In DNA replication, the strands separate
Enzymes use each strand as a template to assemble the new strands A A
Nucleotides
Parental molecule of DNA
Both parental strands serve as templates
Two identical daughter molecules of DNA
Figure 10.4A

15. Untwisting and replication of DNA
Figure 10.4B

16. 10.5 DNA replication: A closer look
DNA replication begins at specific sites
Parental strand
Origin of replication
Daughter strand
Bubble
Two daughter DNA molecules
Figure 10.5A

17. Each strand of the double helix is oriented in the opposite direction
5 end
3 end P P P P P P P P
3 end
5 end
Figure 10.5B

18. Overall direction of replication3
DNA polymerase molecule
How DNA daughter strands are synthesized
5 end 5
Daughter strand synthesized continuously
Parental DNA 5 3
Daughter strand synthesized in pieces 3 P 5
The daughter strands are identical to the parent molecule 5 P 3
DNA ligase
Overall direction of replication
Figure 10.5C