1. The Molecular Basis of Inheritance 26 October, 2005 Text Chapter 16

2. What is the genetic material?
It could be DNA or protein. Transformation of bacterial cells must involve transfer of genetic material.
Since bacterial DNA, but not bacterial protein is capable of transforming R to S, DNA must be the genetic material.

3. DNA and not protein in injected into cells by phage.

4. Hershey and Chase, 1952

5. DNA Structure
Each DNA molecule is a linear polymer of nucleic acid monomers.
The DNA backbone consists of ribose and phosphate groups. This part of the molecule is the same for every monomer.
The variable part of DNA consists of four different nitrogenous bases attached to the C1 of the ribose ring.

6. Base Pairing
Two DNA molecules with complementary sequences can form a double helix. This structure is only possible when the sequence of bases on the two strands allow base pairing over an extended region.

7. The two strands (molecules) in a DNA duplex are antiparallel.

8. Base Pairing

9. The complementary nature of a DNA duplex allows each strand to serve as the template for the synthesis of its partner.

10. Semiconservative Replication
In living systems, DNA replication is semiconservative. Each daughter duplex contains one old and one newly synthesized strand.

11. Semiconservative Replication

12. Replication Origins, Forks, and Bubbles
DNA replication begins at each of several origin sequences. Replication proceeds until the entire double-stranded molecule has been replicated.

13. DNA monomers are triphosphates that are hydrolyzed in the process of polymerization.

14. This means that DNA molecules can only grow in the 5’ to 3’ direction.

15. DNA Synthesis
At each replication fork, there are two strands of DNA to be synthesized.
From the point of view of the leading strand, the fork moved in the 5’ to 3’ direction.
From the point of view of the lagging strand, fork movement is in the 3’ to 5’ direction.

16. Priming
Since DNA synthesis requires a free 3’ OH group, DNA synthesis begins with the synthesis of an RNA primer.
This primer is replaced by DNA later.

17. DNA Synthesis