2. 2A. Distinguish between DNA and RNA.
DNA Replication (12.2)
State Standards
2A. Distinguish between DNA and RNA.
2B. Explain the role of DNA in storing and transmitting cellular information.

3. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Overview
DNA has the unique ability to make an exact copy of itself in a process
called replication.

4. Semiconservative Replication
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Semiconservative Replication
Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and
one strand of new DNA.

5. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Step 1: Unwinding
DNA helicase, an enzyme, breaks the hydrogen bonds holding the base pairs together. It unwinds and unzips the double helix, allowing new nucleotides to bind to the 2 single strands by base pairing.

6. Step 1: Unwinding Cont’d
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Step 1: Unwinding Cont’d
As the double helix is unwound & unzipped, RNA primase adds a short segment of RNA, called an RNA primer (starter), on each DNA strand.

7. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Step 2: Base pairing
DNA polymerase then adds complementary nucleotides to the chain. This continues until the entire molecule has been replicated.

8. Step 2: Base Pairing Cont’d
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Step 2: Base Pairing Cont’d
One strand is called the leading strand & is built continuously.
The other strand is called the lagging strand & is built discontinuously in small fragments (Okazaki fragments).

10. DNA ligase links the two sections.
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Step 3: Joining
DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides.
DNA ligase links the two sections.
Each new strand is half original DNA & half new
DNA.

11. Chapter 12
Molecular Genetics
12.2 Replication of DNA
Conclusion
There are now 2 copies of the genetic information that will be passed on to new cells through mitosis or to the next generation through meiosis.

12. Eukaryotic vs. Prokaryotic DNA Eukaryotic DNA…
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Eukaryotic vs. Prokaryotic DNA
Eukaryotic DNA…
- is found in the nucleus, coiled into chromosomes.
- unwinds in multiple areas as DNA is replicated.

13. Eukaryotic vs. Prokaryotic DNA Cont’d
Chapter 12
Molecular Genetics
12.2 Replication of DNA
Eukaryotic vs. Prokaryotic DNA Cont’d
Prokaryotic DNA…
- is attached to the plasma membrane or is free-floating.
- is circular & only opens at one origin of replication.
DNA is also found in chloroplasts & mitochondria .

18. Name the small segments of the lagging DNA strand.
Chapter 12
Molecular Genetics
Chapter Diagnostic Questions
Name the small segments of the lagging
DNA strand.
ligase
Okazaki fragments
polymerase
helicase A B C D
CDQ 2

19. Which is not an enzyme involved in DNA replication?
Chapter 12
Molecular Genetics
12.2 Formative Questions
Which is not an enzyme involved in DNA
replication?
DNA ligase
DNA polymerase
hilicase
RNA primer A B C D
FQ 5

20. Standardized Test Practice
Chapter 12
Molecular Genetics
Standardized Test Practice
What does this diagram show about the replication of DNA in eukaryotic cells?
DNA is replicated only at certain places along the chromosome.
DNA replication is both semicontinuous and conservative.
Multiple areas of replication occur along the chromosome at the same time.
The leading DNA strand is synthesized discontinuously. A B C D
STP 1