DNA & Replication IN 91 & 93 Headings Vocabulary Important Words

NUCLEUS CHROMOSOME CHROMATIN DNA

(DeoxyriboNucleic Acid) Structure of DNA (DeoxyriboNucleic Acid) Using critical info from the work of others (Rosalind Franklin & Linus Pauling)… James Watson & Francis Crick made 1st model of DNA in 1953 DNA is a Nucleic Acid (AKA: Organic Compound) DNA is made up of small subunits called: Nucleotides

“YES, THE ENTIRE PICTURE!!!” DRAW THIS IN YOUR NOTES! “YES, THE ENTIRE PICTURE!!!”

What Makes Up DNA? Each nucleotide is made up of: Deoxyribose (sugar) Phosphate group (“P”) Nitrogen Base (4 types) Adenine- A Thymine-T Cytosine- C Guanine-G Purines Pyrimidines Pyrimidines Purines

What Is the “Ladder”? 2 long chains of nucleotides Joined together in the form of a ladder Ladder is twisted in the form of a double helix or spiral

Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Sides of the Ladder = Alternating Deoxyribose (Sugar) & Phosphate s-P-s-P-s-P-etc. Rungs or Steps of ladder = Pairs of Nitrogen Bases A-T or C-G T-A or G-C

How Do Nitrogen Bases Pair Up? Adenine(A) pairs up w/ Thymine(T) Guanine(G) pairs up w/ Cytosine(C) Example: A G C T A C G C A 5’ 3’ 3’ A T G C G T 5’ T C G

Why Do Organisms Look So Different? All organisms have the same type of nucleotides Nucleotide arrangement provides for all the different types of organisms Ex: A mouse and a rosebush have the same nucleotides…but… Different Nucleotide Order = Different Organism!!! *This sequence of nucleotides = GENETIC CODE

Replication of DNA During cell division a copy of DNA must be made When new cells are formed each new cell gets an exact copy of the genetic information. This copy of DNA is made through a process known as Replication.

Let’s see DNA Replication at Work!

Steps of Replication During replication, each strand serves as a pattern to make new DNA molecule. The 2 nucleotide strands separate at base pairs. They unzip like a zipper using DNA Helicase (enzyme) Each strand then builds its opposite strand by base pairing with nucleotides that float freely in the nucleus. Each new DNA molecule has 1 nucleotide strand from the original DNA molecule and 1 nucleotide strand made from free nucleotides in the nucleus.

DNA Replication Original strand DNA polymerase New strand Growth Replication fork Replication fork Nitrogenous bases New strand Original strand