TAKS Objective 2 TEKS 6B (DNA Replication) Presented by: Alexander Fedorov Composite Science Teacher Lesson Title: Applicable Text: Handouts

Why Must DNA Replicate? Why Must DNA Replicate? Every time a cell divides, it must first make a copy of it’s chromosomes. (during interphase) Every time a cell divides, it must first make a copy of it’s chromosomes. (during interphase) Therefore, each cell Therefore, each cell can have a complete set of chromosomes. This process is called DNA Replication.

Without replication, species could not survive and individuals could not successfully grow and reproduce. Without replication, species could not survive and individuals could not successfully grow and reproduce.

II. How DNA Replicates II. How DNA Replicates DNA is a molecule composed of TWO compliment strands, each consisting of a sequence of nucleotides that compliment each other. DNA is a molecule composed of TWO compliment strands, each consisting of a sequence of nucleotides that compliment each other. The order of the nitrogen bases on one strand mandates the sequence of bases on the complementary strand. The order of the nitrogen bases on one strand mandates the sequence of bases on the complementary strand.

If you know the bases on one strand, you can predict which bases will occur on the complementary strand. A----- G T----- C----- T----- During Replication each strand serves as a template to create a new strand. This is as easy as break dancing!

III. Steps In Replication III. Steps In Replication 1) Enzymes break down the hydrogen bonds between the two DNA strands, therefore unzipping the molecule. 1) Enzymes break down the hydrogen bonds between the two DNA strands, therefore unzipping the molecule.

2) As the DNA unzips, free nucleotides (from surroundings in the nucleus) bond to the single strands by base pairing (A-T, G- C). 2) As the DNA unzips, free nucleotides (from surroundings in the nucleus) bond to the single strands by base pairing (A-T, G- C).

3) Another Enzyme bonds the new nucleotides into a chain 3) Another Enzyme bonds the new nucleotides into a chain ** The result of this process is the formation of TWO DNA molecules, each identical to the original molecule. Replication! Rah,Rah, Rah!

A-T-T-C-G-T-T-A-C-G-G-A-T-T-C-G-G What is the complimentary strand that is associated with this DNA molecule?