DNA

Objective: SWBAT remember the basic components and structure of DNA Warm-up: What comes to mind when you see DNA?

What is the purpose of DNA? 1. To store information and give it to the cell. – The information specifies what proteins to make, which determines what the cell does. – DNA is the “code of life.” 2. Pass a copy of the information to newly made cells. – Replication

DNA Deoxyribonucleic Acid Deoxyribonucleic Acid Composed of nucleotides: Composed of nucleotides: – sugar (Deoxyribose) – phosphate group – nitrogen base (adenine, guanine, cytosine, or thymine) Purines = adenine (A) and guanine (G) Purines = adenine (A) and guanine (G) Pyrimidines = thymine (T) and cytosine (C) Pyrimidines = thymine (T) and cytosine (C)

DNA Chargaff’s Data: OrganismATGC Human30.4%30.1%19.6%19.9% sheep29.3%28.3%21.4%21.0% Sea urchin 32.8%32.1%17.7%17.3% Salmon29.7%29.1%20.8%20.4% wheat27.3%27.1%22.7%22.8% E Coli 24.7%23.6%26.0%25.7% Lamda Virus 21.3%22.9%28.6%27.2%

Chargaff’s Conclusions A:T = 1 A:T = 1 C:G = 1 C:G = 1 A+G = C+T A+G = C+T A+T:C+G does not = 1 A+T:C+G does not = 1 Inferences? Inferences? – A and T will pair together and G and C will pair together

Structure of DNA Discovered by Watson and Crick in 1953 Discovered by Watson and Crick in 1953 Discovered that DNA is a Double Helix with the help of Rosalind Franklin Discovered that DNA is a Double Helix with the help of Rosalind Franklin

Structure of DNA Double helix = 2 nucleotide chains wrapped around each other like a twisted ladder Double helix = 2 nucleotide chains wrapped around each other like a twisted ladder Alternating deoxyribose sugar and phosphate molecules form the backbone = the rails of the ladder Alternating deoxyribose sugar and phosphate molecules form the backbone = the rails of the ladder Backbone is held together by strong covalent bonds so the bases stay in the right order Backbone is held together by strong covalent bonds so the bases stay in the right order

Structure of DNA Complementary Base pairs Complementary Base pairs – Adenine and Thymine – Guanine and Cytosine Base pairs connect the strands by hydrogen bonds that are easy to break Base pairs connect the strands by hydrogen bonds that are easy to break – This forms the steps of the ladder This allows the DNA to unzip when it needs to be read to make a protein or copy itself This allows the DNA to unzip when it needs to be read to make a protein or copy itself

DNA is the code of life There are 4 different types of bases. There are 4 different types of bases. The bases are like letters of a word. The bases are like letters of a word. Every 3 bases spells out the code for one amino acid. Every 3 bases spells out the code for one amino acid. Put enough amino acids together and you get words and eventually you get a sentence Put enough amino acids together and you get words and eventually you get a sentence – In this case, one protein. A segment of DNA that codes for one protein is called a “gene.” A segment of DNA that codes for one protein is called a “gene.” Genes determine what your structure is like and what shape your enzymes are. Genes determine what your structure is like and what shape your enzymes are.

Let’s Review! What are the 2 functions of DNA? What are the 2 functions of DNA? – Store and give information to cells to make proteins, and to pass that information to new cells What makes up the backbone (the rails) of the ladder? What makes up the backbone (the rails) of the ladder? – Alternating sugars and phosphates What type of bond holds them together? What type of bond holds them together? – Covalent bonds because they are strong and you want the DNA to stay in the right order.

Let’s Review! Nucleotides Nucleotides What 3 things are a nucleotide made of? What 3 things are a nucleotide made of? – Sugar, phosphate, base What are the 4 types of nitrogen bases? What are the 4 types of nitrogen bases? – Adenine (A), Thymine (T), Guanine (G), Cytosine (C) What pairs with what? What pairs with what? – A and T, G and C What type of bond helps make the steps of the ladder? What type of bond helps make the steps of the ladder? – Hydrogen

Objective: Students will be able to apply the base pairing rules to DNA model making and replication. Student will be able to discuss why DNA is the carrier for genetic material and not protein. Warm Up: What is the backbone of DNA made out of? What kind of bond holds it together?

Why DNA and not Protein? Why DNA and not Protein? When scientists were first looking for what carried genetic information they thought it might be protein. When scientists were first looking for what carried genetic information they thought it might be protein. – Protein has 20 amino acids for a more complex code – DNA only has 4 different nitrogen bases

Griffith Inferences? Inferences? Griffith discovered transformation the ability of bacteria to pick up genetic information from their environment. Griffith discovered transformation the ability of bacteria to pick up genetic information from their environment.

Avery Experiment 1: S cells exposed to Protease (destroys protein) added to R cells  Mouse dies Experiment 1: S cells exposed to Protease (destroys protein) added to R cells  Mouse dies Experiment 2: S cells exposed to RNase (destroys RNA) added to R cells  Mouse dies Experiment 2: S cells exposed to RNase (destroys RNA) added to R cells  Mouse dies Experiment 3: S cells exposed to DNase (Destroys DNA) added to R cells  mouse LIVES!! Experiment 3: S cells exposed to DNase (Destroys DNA) added to R cells  mouse LIVES!!

Hershey- Chase Experiment Martha Chase and Alfred Hershey knew that Bacteriophages (a type of Virus) injected their genetic information in to E. coli for replication. Martha Chase and Alfred Hershey knew that Bacteriophages (a type of Virus) injected their genetic information in to E. coli for replication.

DNA Replication G C T T G G G C T G C T T G G G C T I only have one strand of DNA. How do I figure out what the other strand of DNA is?

DNA Replication Double helix unwinds to make 2 single strands. Double helix unwinds to make 2 single strands. Enzymes add new nucleotides (red blocks) to make a complimentary strand. Enzymes add new nucleotides (red blocks) to make a complimentary strand. The DNA has now copied itself. The DNA has now copied itself. Replication is Semi- conservative: Each new set of DNA has one original strand (black) and one newly made strand (red). Replication is Semi- conservative: Each new set of DNA has one original strand (black) and one newly made strand (red).

Steps of DNA Replication Nucleotide chain unwinds Nucleotide chain unwinds Separated by enzymes called Helicases (break apart hydrogen bonds) Separated by enzymes called Helicases (break apart hydrogen bonds) DNA Polymerases (enzymes) attach the matching nucleotides, and two new exact copies of DNA are formed DNA Polymerases (enzymes) attach the matching nucleotides, and two new exact copies of DNA are formed

DNA Replication DNA only replicates when the cell is going to divide. DNA only replicates when the cell is going to divide. – In every cell, there are 2.3 meters of DNA (3 billion base pairs). The entire process is extremely accurate. The entire process is extremely accurate.