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BiologyBiology

DNA ReplicationDNA Replication

ItineraryItinerary

Topics for todayTopics for today ReviewReview DNA ReplicationDNA Replication

OverviewOverview In DetailIn Detail

ReviewReview1. Name the four classes of biomolecules

ReviewReview1. Name the four classes of biomolecules2. Define ‘monomer’ and ‘polymer.’

ReviewReview1. Name the four classes of biomolecules2. Define ‘monomer’ and ‘polymer.’3. What is a nucleotide?

ReviewReview1. Name the four classes of biomolecules2. Define ‘monomer’ and ‘polymer.’3. What is a nucleotide?4. What are the three components of a nucleotide?

Structure of DNA/RNA (1)Structure of DNA/RNA (1)

Three Components

1)Phosphate Group

1)‘Pentose Sugar’

1)Nitrogenous base

ReviewReview1. Name the four classes of biomolecules2. Define ‘monomer’ and ‘polymer.’3. What is a nucleotide?4. What are the three components of a nucleotide?5. What is the difference between the purines and the

pyrimidines?


You need to remember these!


pyrimidines?


Deoxyribose and Ribose are both 5 carbon sugars


pyrimidines?6. Base Pairing

Gary Coleman

Gary Coleman

Guanine-Cytosine

Gary Coleman Alex Trebek

Guanine-Cytosine Adenine-Thymine

DNA Replication-DNA Replication- Overview (1) Overview (1)

In Text- p 298In Text- p 298


In Text- p 298In Text- p 298 Step 1: The Double Helix is unzippedStep 1: The Double Helix is unzipped


In Text- p 298In Text- p 298 Step 1: The Double Helix is unzippedStep 1: The Double Helix is unzipped Step 2: Each strand directs the synthesis of two Step 2: Each strand directs the synthesis of two

new strandsnew strands


In Text- p 298In Text- p 298 Step 1: The Double Helix is unzippedStep 1: The Double Helix is unzipped Step 2: Each strand directs the synthesis of two Step 2: Each strand directs the synthesis of two

new strandsnew strands Step 3: The individual nucleotides are Step 3: The individual nucleotides are

connected to form two new strandsconnected to form two new strands

Semiconservative Replication (1)Semiconservative Replication (1)Process of DNA replicationis called ‘semiconservativereplication


Make sure you know this term. You’ll see it again!


This means that in each new double helix of DNA, one strand was from the parent.

Semiconservative Replication (4)Semiconservative Replication (4)

Semiconservative Replication (7)Semiconservative Replication (7)How do we know that DNA replicates with a ‘Semiconservative’ nature?


Any ideas?


Any ideas?

Meselson-Stahl experiment tested the three hypotheses for DNA replication

Semiconservative Replication (8)Semiconservative Replication (8)Meselson-Stahl ExperimentMeselson-Stahl Experiment


Where is the 15N found?


Remember, DNA replication is the process of Remember, DNA replication is the process of making copies of DNA.making copies of DNA.



When would the cell do this?When would the cell do this?



When would the cell do this?When would the cell do this? Now we need to look at the specifics of DNA Now we need to look at the specifics of DNA

replication, and the replication, and the enzymes enzymes involved in each involved in each stepstep

But First, What’s an Enzyme?But First, What’s an Enzyme?


A type of ProteinA type of Protein


A type of ProteinA type of Protein Text Definition:Text Definition:

A class of proteins serving as catalysts, chemical A class of proteins serving as catalysts, chemical agents that change the rate of a reaction without agents that change the rate of a reaction without being consumed within the reactionbeing consumed within the reaction

Step 1: Separation of the Double Step 1: Separation of the Double HelixHelix


DNA Helicase unwinds the double helix•The site where the enzyme begins

replication is called the origin of replication.


DNA Helicase unwinds the double helix•The site where the enzyme begins

replication is called the origin of replication.

•In Prokaryotes (Bacteria), there is a single origin; in eukaryotes, there are thousands

Step 2: Synthesis of complementsStep 2: Synthesis of complements

Step 2: Synthesis of complementsStep 2: Synthesis of complementsEnzyme- DNA polymerase


•DNA polymerase allows the new nucleotides to be added to the growing end of the strand one by one


•DNA polymerase allows the new nucelotides to be added to the growing end of the strand one by one

•NOTE: This new synthesis always occurs in the same direction, 5’3’

DNA directionalityDNA directionality

DNA directionalityDNA directionality

A new nucleotide is always added to the 3’ endof the strand

Synthesis of Complementary strandsSynthesis of Complementary strands

Enzymes InvolvedEnzymes Involved

1) Helicase1) Helicase


1)1) HelicaseHelicase

2)2) Single Stranded Binding ProteinSingle Stranded Binding Protein




3)3) PrimasePrimase




3)3) PrimasePrimase

4)4) DNA polymeraseDNA polymerase




3)3) PrimasePrimase

4)4) DNA polymeraseDNA polymerase

5)5) LigaseLigase

DNA Replication-SummaryDNA Replication-Summary

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