DNA Structure Review and DNA Replication

Warm-Up – 5 minutes 1)What are the 3 parts of a nucleotide? 2)Which part of the nucleotide is the “genetic code?” 3)What is Chargaff’s base pairing rule? 4)How did Chargaff determine which base pairs with which base? (look at your notes)

Stop and Check: Answer on your warm-up sheet of paper. 1)What does DNA stand for? 2)What kind of sugar does DNA have? 3)What kind of bond holds together the sugars and phosphates? 4)What kind of bond holds together the bases? 5)Where does DNA replication occur?

Let’s Review DNA Structure Click here for Journey of DNA Click here for Journey of DNA

Double Helix These nucleotides are arranged in the shape of a double helix (a two-sided, twisted ladder.) Who was responsible for the first double helix model? How many nucleotides do you see? Notice Chargaff’s Base Pairing Rule: A-T and C-G

More Structure Facts: Sugars and phosphates make up the sides of the ladder Strong covalent bonds connect the sugars and phosphates The nitrogen bases make the steps of the ladder Weak hydrogen bonds connect the bases The order of the bases determines what proteins are made (we’ll talk more about this later!)

DNA NAME Deoxyribonucleic Acid TYPE OF SUGAR Deoxyribose NITROGEN BASES Adenine Thymine Cytosine Guanine SHAPE Double Helix

DNA Replication

DNA Replication – Makes a copy Brainstorm - Why would DNA make a copy of itself? Answer- Before a cell divides, it must make sure that each new cell receives its own DNA copy. Brainstorm – What would happen if a cell divided and did not get a copy of the DNA?

Where Does Replication Occur? …in the nucleus ALL DNA activities take place there.

Step 1 of DNA Replication : Answer: The weak hydrogen bonds are broken by the enzymeThe weak hydrogen bonds are broken by the enzyme DNA unwinds and unzipsDNA unwinds and unzips Enzyme Partner Share - What happened between diagram 1 and diagram 2? Diagra m 1 Diagram 2

Step 2 of DNA Replication Answer: Free floating nucleotides in the nucleus attach to the exposed New bonds form Replication Fork Partner Share - What is happening now?

Partner Share - What is the end product of DNA Replication? What does “Old” and “New” refer to in the diagram?

Answer- 2 identical copies of DNA are made “Old” is part of the original DNA strand “New” is the new strand made during the process