8.3 DNA Replication•Set up Cornell Notes on pg. 5

•Topic: 8.3 DNA Replication

•Essential Question:

1.Explain how DNA serves as its own “template” during replication.

2.1 Atoms, Ions, and Molecules

1. Explain how DNA serves as its own “template” during replication.

8.3 DNA Replication

Key Concept: DNA replication copies the genetic information of a cell.

8.3 DNA Replication

• EQ: This is a template (guide to follow)

8.3 DNA Replication

1. What stage of the cell cycle does DNA replication occur?

2. Why is it important that the DNA is replicated before mitosis occurs?

3. Following the base-pairing rules, please complete the two DNA sequences below :

T A C G T A T G A A A C

T G G T T T A G A A T T

On the top ¼ of pg. 4: REVIEW

8.3 DNA Replication

T A C G T A T G A A A C

A T G C A T A C T T T G

T G G T T T A G A A T T

A C C A A A T C T T A A

What stage of the cell cycle does DNA replication occur?•S stage or Synthesis

Why is it important that the DNA is replicated before mitosis?•Each cell must have a full set of DNA

8.3 DNA Replication

Connect

• Do you know that your cells are dying right now?

• You may live to 100, but most of your cells will have been replaced thousands of times before then

• Every time that cells divide to produce new cells, DNA must first be copied in a remarkable process of unzipping and zipping by enzymes and other proteins. Mitosis

8.3 DNA Replication

KEY CONCEPT DNA replication copies the genetic information of a cell.

8.3 DNA Replication

What does the word replication mean?

• A copy or reproduction.

8.3 DNA Replication

original strand new strand

Two molecules of DNA

complementary

• DNA Replication copies the genetic information so that we have two identical strands of DNA.

What does identical mean???? Exactly the same!

8.3 DNA Replication

• The rules of base pairing directreplication.

• A=T

• C=G

Remember: What are our base pairing rules?

8.3 DNA Replication

• Enzymes and other proteins do the actual work of replication.1. The enzyme Helicase “unzips” the double helix

(Hydrogen bonds now broken between the bases)

– “Free-floating” nucleotides form hydrogen bonds with the original or “parent” strand ( acts as our template).

8.3 DNA Replication

unzips

nucleotides

Helicase

a fragment of DNA

Make a Key: original strand and new strand in 2 different colors

Original/Parent strand New “Complementary” Daughter strand

8.3 DNA Replication

2. DNA polymerase (pol-uh-muh-rays) enzymes bond the nucleotides together to “complementary” bases to form the double helix.

Complementary =Go together Ex: A-T C-G

What do you think they mean by “complementary”?

8.3 DNA Replication

DNA polymerase

new strand

nucleotide

complementary

5’3’

5’ 3’

• The DNA Polymerases, add nucleotides only to the 3’ (3 Prime) end of the strand

8.3 DNA Replication

3. Two identical molecules of DNA are formed, each with an original strand and a “complementary” newly formed strand.

complementary

Why do we call the new “daughter” strand complementary and not identical to the “parent” or original strand?

original strand new strand

Two molecules of DNA

8.3 DNA Replication

original strand new strand

Two molecules of DNA

complementary

• Because they are not identical! • Ex: Where the parent strand has an “A” the daughter strand will

have…• “T”

8.3 DNA Replication

original strand new strandnew “daughter” strandOriginal “parent” strand

Complementary

Conserving the original strand = semiconservative

8.3 DNA Replication

original strand new strand

Two molecules of DNA

DNA is called semiconservative because one original strand is conserved, and one complementary new strand is made.

complementary

What does it mean if you “Conserve” something? You save it!

8.3 DNA Replication

Homework

• On the back of your DNA Replication picture page please follow your base-pairing rules and complete the unzipped strand of DNA. – Follow the color-coding guide

– if you need to, change the key to meet your color needs

8.3 DNA ReplicationMarshmallow DNA Replication Activity

8.3 DNA Replication

There are many origins of replication in eukaryotic chromosomes.

• DNA replication starts at many points in eukaryotic chromosomes.

Replication is fast and accurate.

• DNA polymerases can find and correct errors.

8.3 DNA Replication

DNA Replication Video