DNA Replication SC 912 L 16 3 Describe

DNA Replication SC. 912. L. 16. 3 - Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic information

DNA REP • Objective: Recall the components and structure of DNA and Describe the process of DNA replication and its role in the transmission and conservation of genetic information. • EQ: How does the process of DNA replication allow for information to be retained and transferred?

Structure of DNA Quick review! DNA and Nucleotides… • Which is the polymer and which is the monomer? Nucleic acids (DNA) = polymer Nucleotides = monomer • What is the structure of a nucleotide? DNA? Nucleotide- phosphate, sugar, nitrogen base DNA- double helix (spiral) • What is the function of N. A. ? Store genetic info

Developments in DNA Structure • Erwin Chargaff: determined that different organisms have the same 4 bases but in different ratios – Also noted that the amounts of C and G were relatively the same; A and T were also the same • James Watson, Francis Crick: developed accurate model of DNA’s double helix structure – Used info from x-ray crystallography • Rosalind Franklin, Maurice Wilkins: looked at the structure of DNA using x-ray crystallography

Structure of DNA • Deoxyribose Nucleic Acid (DNA) is made up of the monomer: nucleotides • Each nucleotide has 3 parts: – Phosphate group – Deoxyribose (sugar) – Nitrogen-containing base

DNA Structure • 4 Nucleotides (bases): 1. Adenine (A) 2. Guanine (G) 3. Cytosine (C) 4. Thymine (T)

Structure of DNA (Honors) • The only difference between the nucleotides is the nitrogencontaining base – Pyrimidines have single rings (thymine and cytosine) – Purines have double rings (adenine and guanine)

Structure of DNA • Single-ring bases pair with double-ring bases to form a double helix (spiral ladder) – Sugar-phosphate backbones form sides of ladder – Nitrogen bases pair to form the rungs of the ladder • Base Pairing Rules: – A pairs with T – C pairs with G

Base Pairs (Honors) • Nucleotides in a single strand are joined by covalent bonds (sugar and phosphate) • Nucleotides on separate strands (base pairs, two stands) are held together by hydrogen bonds hydrogen bond covalent bond

Base-Pairs Practice • Which base would be paired with… • Adenine • pairs with thymine

Base-Pairs Practice • Which base would be paired with… • Cytosine • pairs with guanine

Base-Pairs Practice • Which base would be paired with… • Thymine • pairs with adenine

Base-Pairs Practice • Write the sequence of nucleotides that would be paired with the first strand C–T–A–G–G G–A–T–C–C

DNA Replication • DNA only stores genetic information and acts as a template; • Specialized proteins are used to replicate the DNA • Each single strand of DNA can be used as a template for a new strand • All cells have a complete set of DNA – Different types of cells express the genes differently, but all cells still have ALL DNA

Process of Replication 1. Enzymes (helicase) unzip the double helix at origins of replication - Occurs in multiple locations on the eukaryotic strand of DNA

Process of Replication 2. As lone nucleotides are exposed by the unzipping of the DNA, enzymes (DNA Polymerases) pair free-floating nucleotides in the nucleus with the bases on the original strand new strand nucleotide DNA polymerase

Process of Replication 3. The result is two identical strands of DNA - One side of each strand is the original strand (template) - The other side of the strand is the newly-synthesized complementary strand original strand Two molecules of DNA new strand

How do you eat DNA-spaghetti? With a replication fork

Semiconservative Replication • The process of DNA replication is semiconservative – Each DNA strand is half of the original and half replicated (new) – Conservative replication would have one copy of the DNA with both original strands; the other copy of DNA would have both new strands • Proofreading: enzymes (DNA polymerases) check for errors, replace mismatched nucleotides

Think, Pair, Share • Why is it important for the process of DNA replication to be accurate? – To prevent genetic mutations • Where is DNA in the cell? Where does DNA rep take place? – In the Nucleus

Left Side Activity! Modeling the structure of DNA… WITH CANDY!!! Using twizlers, gummy bears, and toothpicks, go through the process of DNA replication. • C- level 2, talk to your table partner • H- ask three before me • A- using provided materials, go through the process of DNA Replication • M- Remain seated in your assigned seat • P- create and replicate your own DNA strand • Success

LAB: QKA During DNA replication two identical DNA molecules are produced from one original molecule. Which statement below explains why the newly formed molecules are identical to the original? A. The original DNA molecule breaks down into nucleotides that are reassembled by DNA polymerase into two new molecules. B. The nitrogen base adenine can only pair with cytosine and thiamine. C. Each strand of the original molecule serves as a template for the two new stands, and new nucleotides are added to the template according to the pairing rule. D. The nitrogen base adenine can only pair with guanine and phosphate groups.

Exit ticket • Clear your desk of everything except something to write with and your DO NOW.