DNA “The Secret of Life”

Basic Bases of DNA Four Main Bases: (Nitrogenous Bases) 1)Adenine 2)Guanine 3)Cytosine 4)Thymine 5)Known as A, T, C, G

Purines and Pyrimidines Adenine and Guanine are purines. 2 carbon ringsAdenine and Guanine are purines. 2 carbon rings Thymine and Cytosine are pyrimidines. 1 carbon ringThymine and Cytosine are pyrimidines. 1 carbon ring

Nucleotide The nucleotide is the basic unit of a DNA molecule.The nucleotide is the basic unit of a DNA molecule. It has 3 parts:It has 3 parts: 1) Nitrogen Base (A, T, C, G)1) Nitrogen Base (A, T, C, G) 2) Phosphate Group2) Phosphate Group 3) Sugar (Deoxyribose)3) Sugar (Deoxyribose)

Double Helix DNA is a double helix, meaning there are 2 strands connected together by hydrogen bonds!!DNA is a double helix, meaning there are 2 strands connected together by hydrogen bonds!! It has a spiral shape like the border on the left.It has a spiral shape like the border on the left. The two strands are anti- parallel, meaning they run in opposite directions.The two strands are anti- parallel, meaning they run in opposite directions.

Base Pair Rules Adenine pairs with ThymineAdenine pairs with Thymine A with TA with T Guanine pairs with CytosineGuanine pairs with Cytosine G with CG with C Chargaff’s Rule!Chargaff’s Rule!

DNA Replication “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”“It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” J.D. WatsonJ.D. Watson F. H. C. CrickF. H. C. Crick

What is DNA replication? The process of producing two identical strands/molecules of DNA.The process of producing two identical strands/molecules of DNA. Each DNA molecule will have the same sequence.Each DNA molecule will have the same sequence.

Enzymes There are many enzymes that help DNA replication work.There are many enzymes that help DNA replication work. The important ones you need to know are:The important ones you need to know are:

1. DNA polymerase: reads the original template strand and inserts the correct nucleotide using the base pair rules.1. DNA polymerase: reads the original template strand and inserts the correct nucleotide using the base pair rules. Adenine with ThymineAdenine with Thymine Guanine with CytosineGuanine with Cytosine See Board

2. Helicase: opens up the DNA molecule. Unwinds the helix.2. Helicase: opens up the DNA molecule. Unwinds the helix. Simply creates the room to do replication.Simply creates the room to do replication. 3. Ligase: links copied DNA fragments together.3. Ligase: links copied DNA fragments together.

Where? At replication forks! The point where the double strand DNA is splitting into 2 single strands.At replication forks! The point where the double strand DNA is splitting into 2 single strands.

Steps 1. Helicase: unwinds helix1. Helicase: unwinds helix 2. DNA polymerase uses an original template strand to create a complementary strand going towards the replication fork. Always works in 5’ to 3’ direction.2. DNA polymerase uses an original template strand to create a complementary strand going towards the replication fork. Always works in 5’ to 3’ direction.

3. The lagging strand (moving away from the repl. Fork) is made in several fragments.3. The lagging strand (moving away from the repl. Fork) is made in several fragments. 4. Ligase: connects the fragments on the lagging strand.4. Ligase: connects the fragments on the lagging strand.

Semi-conservative 1. Original strand is a template to be copied. (like stencil)1. Original strand is a template to be copied. (like stencil) 2. After replication there are two ds DNA molecules.2. After replication there are two ds DNA molecules. 3. Each molecule will have an orginal parent strand and a newly made strand.3. Each molecule will have an orginal parent strand and a newly made strand. See BoardSee Board

DNA makes DNADNA makes DNADNA makes DNA makes DNA