8.3 DNA Replication First Five 2/10 1.Without using your lab, who were the people, in order, that discovered the structure of DNA? 2.Turn in your lab notebook to the bin behind Kringle’s computer. Schedule 1.First Five 2.DNA notes HW: 1.Discovering DNA Lab – Due Today 2.DNA Molecule/Replication wkst – due Friday GQ2: How does DNA’s structure relate to its function?

8.3 DNA Replication First Five 2/4 1.Who do you think contributed the most to the discovery of DNA’s structure and Why? - Watson/Crick - Franklin - Wilkins - Pauling - Chargaff 2. Turn in your lab notebook to the bin behind Kringle’s computer. Schedule 1.First Five 2.Finish Movie 3.Letter Assignment HW: Letter Due Friday GQ: How does DNA’s structure relate to its function?

8.3 DNA Replication Choose one of the following letters to write. 1.Write a letter to James Watson as Rosalind Franklin, detailing your disappointment for not receiving credit for providing pertinent information for DNA’s structure. 2.Write a letter to Rosalind Franklin as Maurice Wilkins, detailing why Franklin should have received credit for DNA’s structure. 3.Write a letter to the Nobel Prize committee as Rosalind Franklin, detailing your contributions to Watson and Crick’s discovery of DNA structure.

8.3 DNA Replication First Five 2/4 1.Without your movie notes; what did the following people discover about DNA’s Structure? - Watson/Crick - Franklin - Wilkins - Pauling - Chargaff Schedule 1.First Five 2.Quiz – Cell Cycle 3.Replication Notes 4.Replication Lab HW: DNA Molecule – Due Thurs DNA Replication – Due Thurs GQ: How is DNA replicated?

8.3 DNA Replication DNA is composed of four types of nucleotides. DNA is made up of a long chain of nucleotides. Each nucleotide has three parts. –a phosphate group –a deoxyribose sugar –a nitrogen-containing base phosphate group deoxyribose (sugar) nitrogen-containing base

8.3 DNA Replication The nitrogen containing bases are the only difference in the four nucleotides.

8.3 DNA Replication Watson and Crick determined the three-dimensional structure of DNA by building models. They realized that DNA is a double helix that is made up of a sugar- phosphate backbone on the outside with bases on the inside.

8.3 DNA Replication Watson and Crick’s discovery built on the work of Rosalind Franklin and Erwin Chargaff. –Franklin’s x-ray images suggested that DNA was a double helix of even width. –Chargaff’s rules stated that A=T and C=G.

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

8.3 DNA Replication Remember that a cell’s DNA needs to replicate (duplicate) before the cell can divide. Write a hypothesis proposing how DNA replicates.

8.3 DNA Replication T A C G Nucleotides always pair in the same way. Chargaffs Rules: –#A = #T –#G = #C The base-pairing rules show how nucleotides always pair up in DNA. Because a pyrimidine (single ring) pairs with a purine (double ring), the helix has a uniform width. – A pairs with T – C pairs with G

8.3 DNA Replication The backbone is connected by covalent bonds. hydrogen bond covalent bond The bases are connected by hydrogen bonds.

8.3 DNA Replication Replication copies the genetic information. A single strand of DNA serves as a template for a new strand. The rules of base pairing direct replication. DNA is replicated during the S (synthesis) stage of the cell cycle. Each body cell gets a complete set of identical DNA.

8.3 DNA Replication First Five 2/5 1.What is the monomer of DNA? 2.Write a hypothesis as to how DNA is replicated. Schedule 1.First Five 2.Replication Notes 3.Replication Lab HW: DNA Molecule – Due Tomorrow DNA Replication – Due Tomorrow Cell Cycle Quiz Make up – Due Friday GQ: How is DNA replicated?

8.3 DNA Replication Proteins carry out the process of replication. DNA serves only as a template. Enzymes and other proteins do the actual work of replication. 1. Enzymes unzip the double helix. (Helicase) 2. Free-floating nucleotides form hydrogen bonds with the template strand. nucleotide The DNA molecule unzips in both directions.

8.3 DNA Replication –DNA Polymerase fixes misplaced nucleotides in the new strand. 3. DNA polymerase enzymes bond the nucleotides together in the new strand (covalent bonds between sugars and phosphates) to form the double helix. DNA polymerase new strand nucleotide

8.3 DNA Replication DNA replication is semiconservative. original strand new strand Two molecules of DNA Two new molecules of DNA are formed, each with an original strand and a newly formed strand.

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 First Five 2/6 1.What two enzymes are involved in replication? 2.Take out your DNA molecule and DNA Replication wksts. Schedule 1.First Five 2.Replication Lab/ Oral Quizzes 3.Clean Up HW: DNA Molecule – Due Today DNA Replication – Due Today Cell Cycle Quiz Make up – Due Friday Test/Test Packet – Due Thurs 2/13 Review – Due Wednesday 2/12 GQ: How is DNA replicated?

8.3 DNA Replication Questions 1.In step 1 of replication, how does the DNA unzip? 2.In step 2 of replication, how do the new strands compare with the template strands? 3.What enzyme is important in step 2? 4.What is the result of DNA replication? 5.Why is it important for the cell to correct any errors that occur during replication?

8.3 DNA Replication Oral Quiz What do we mean when we say that DNA replication is semiconservative? What are the three steps of DNA replication? What happens in each step? What type of molecule creates the bonds between the sugars and the phosphates of the new nucleotides? What type of bond is formed? What do we call the location where DNA replication begins? Where do the free-floating nucleotides come from?

8.3 DNA Replication Why do cells need to divide? 1.Replace old and damaged cells 2.Big cells begin to starve and lack Oxygen 3.Big cells cannot get rid of waste or CO 2 fast enough

8.3 DNA Replication Chromosomes condense at the start of mitosis. DNA wraps around proteins (histones) that condense it. DNA double helix DNA and histones Chromatin Supercoiled DNA

8.3 DNA Replication DNA plus proteins is called chromatin. One half of a duplicated chromosome is a chromatid. Sister chromatids are held together at the centromere. Telomeres protect DNA and do not include genes. Condensed, duplicated chromosome chromatid telomere centromere telomere

8.3 DNA Replication Human Cells have 23 pairs of chromosomes (total 46) Homologous chromosomes –Two chromosomes that have copies of the same genes

8.3 DNA Replication Duplicated vs. Unduplicated Homologous Chromosomes