Warm Up Which of the following is a nucleotide found in DNA? a. ribose + phosphate group + thymine b. ribose + phosphate group + uracil c. deoxyribose + phosphate group + uracil d. deoxyribose + phosphate group + cytosine

Warm Up Which of the following is a nucleotide found in DNA? a. ribose + phosphate group + thymine b. ribose + phosphate group + uracil c. deoxyribose + phosphate group + uracil d. deoxyribose + phosphate group + cytosine

DNA Structure & Replication

Figure 12–1 shows the structure of a(an) a.DNA molecule. b.RNA molecule. c.amino acid. d.protein.

Figure 12–1 shows the structure of a(an) a.DNA molecule. b.RNA molecule. c.amino acid. d.protein.

Let’s Review

What is DNA? Deoxyribonucleic Acid DNA is the molecule involved in inheritance. All the genetic information (instructions) that are used to build your body.

nucleotides Nucleotides are the monomers of nucleic acids. Nucleotides are made of: 5 carbon sugar, phosphate group, and a nitrogenous base

Nitrogenous Bases 4 Nitrogenous Bases: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Pyrimidines- single rings Purines- double rings

Base pairing Adenine pairs with Thymine (A-T) Cytosine pairs with Guanine (C-G)

DNA Structure Shaped like a double helix DNA is compared to a twisted ladder! The steps of the ladder are the paired bases. The rails are sugars and phosphates that alternate.

What does DNA look like in living cells? Let’s extract DNA from some common fruits that we eat so we can see.

You will be given an “template Stand, create the complementary strand . Opening

DNA REPLICATION

Work Session DNA Coloring: Handout DNA History Webquest

Semiconservative replication Parent strands of DNA separate and serve as the template for the new DNA. Each DNA molecule has a parent strand and a new one! Occurs during interphase of mitosis and meiosis.

Antiparallel DNA strands run “antiparallel” to one another. The 5’ (five prime) end has a phosphate group. The 3’ (three prime) end has a sugar.

Step 1: HELICASE unwinds a segment of DNA It “unzips” the double helix

Step 2: RNA Primase attaches to the DNA and synthesizes many short RNA primers

Step 3: DNA Polymerase III adds new nucleotides to the 3’ end of the RNA primer

Leading vs. lagging strands Leading Strand Synthesized continuously from 5’ to 3’ Lagging Strand (Okazaki fragments) Since DNA Polymerase III can only add new nucleotides to the 3’ end of the primer, this strand is synthesized DIScontinuously

Step 4: DNA Polymerase I will then remove the RNA primers and replace them with DNA nucleotides

Step 5: DNA Ligase is a “linking” enzyme that seals the Okazaki fragments together

DNA Replication http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::5 35::535::/sites/dl/free/0072437316/120076/ micro04.swf::DNA%20Replication%20Fork