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

DNA Replication (12.2)

State Standards

2A. Distinguish between DNA and RNA.

2B. Explain the role of DNA in storing and transmitting cellular information.

12.2 Replication of DNA

Molecular Genetics

Overview

Chapter 12

DNA has the unique ability to make an exact copy of itself in a processcalled replication.

12.2 Replication of DNA

Molecular Genetics

Semiconservative Replication Parental strands of

DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA andone strand of new DNA.

Chapter 12

Molecular Genetics

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.

12.2 Replication of DNA

Chapter 12

Molecular Genetics

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.

12.2 Replication of DNA

Chapter 12

Molecular Genetics

Step 2: Base pairing DNA polymerase then adds complementary

nucleotides to the chain. This continues until the entire molecule has been replicated.

12.2 Replication of DNA

Chapter 12

Molecular Genetics

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).

12.2 Replication of DNA

Chapter 12

Step 2: Base Pairing Cont’d

Molecular Genetics

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.

12.2 Replication of DNA

Chapter 12

Molecular Genetics

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.

12.2 Replication of DNA

Chapter 12

12.2 Replication of DNA

Molecular Genetics

Eukaryotic vs. Prokaryotic DNA Eukaryotic DNA…

- is found in the nucleus, coiled into chromosomes.

- unwinds in multiple areas as DNA is replicated.

Chapter 12

12.2 Replication of DNA

Molecular Genetics

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

Chapter 12

1. A2. B3. C4. D

CDQ 2

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Molecular Genetics

Chapter Diagnostic Questions

Chapter 12

A. ligase

B. Okazaki fragments

C. polymerase

D. helicase

Name the small segments of the lagging DNA strand.

1. A2. B3. C4. D

FQ 5

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Molecular GeneticsChapter 12

12.2 Formative Questions

A. DNA ligase

B. DNA polymerase

C. hilicase

D. RNA primer

Which is not an enzyme involved in DNA replication?

1. A2. B3. C4. D

STP 1

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Molecular GeneticsChapter 12

What does this diagram show about the replication of DNA in eukaryotic cells?

Standardized Test Practice

A. DNA is replicated only at certain places along the chromosome.

B. DNA replication is both semicontinuous and conservative.

C. Multiple areas of replication occur along the chromosome at the same time.

D. The leading DNA strand is synthesized discontinuously.