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Understand how DNA serves as its own template during replication. Explore the stages and importance of DNA replication before mitosis. Learn about base-pairing rules and how enzymes work in the process. Discover the concept of complementary strands and the conservation of genetic information in cells. Engage in a hands-on replication activity to deepen your understanding. Dive into the world of DNA replication with this informative guide.
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8.3 DNA Replication 2.1 Atoms, Ions, and Molecules • Set up Cornell Notes on pg. 5 • Topic: 8.3 DNA Replication • Essential Question: • Explain how DNA serves as its own “template” during replication. • Explain how DNA serves as its own “template” during replication. Key Concept: DNA replication copies the genetic information of a cell.
On the top ¼ of pg. 4:REVIEW 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
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 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
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
KEY CONCEPT DNA replication copies the genetic information of a cell.
What does the word replication mean? • A copy or reproduction.
new strand original strand Two molecules of DNA • DNA Replication copies the genetic information so that we have two identical strands of DNA. complementary What does identical mean???? Exactly the same!
The rules of base pairing directreplication. Remember: What are our base pairing rules? • A=T • C=G
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).
unzips Make a Key: original strand and new strand in 2 different colors Original/Parent strand New “Complementary” Daughter strand nucleotides Helicase a fragment of DNA
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”?
nucleotide new strand DNA polymerase • The DNA Polymerases, add nucleotides only to the 3’ (3 Prime) end of the strand 3’ 5’ complementary 5’ 3’
new strand original strand Two molecules of DNA 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?
new strand original strand Two molecules of DNA • Because they are not identical! • Ex: Where the parent strand has an “A” the daughter strand will have… • “T” complementary
new strand original strand Complementary new “daughter” strand Original “parent” strand Conserving the original strand = semiconservative
new strand original 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!
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
There are many origins of replication in eukaryotic chromosomes. Replication is fast and accurate. • DNA replication starts at many points in eukaryotic chromosomes. • DNA polymerases can find and correct errors.