DNA Replication Headings Vocabulary Important Words NUCLEUS CHROMOSOME

DNA & Replication Headings Vocabulary Important Words

NUCLEUS CHROMOSOME CHROMATIN DNA

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

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) Purines • Adenine- A Pyrimidines • Thymine-T Pyrimidines • Cytosine- C Purines • Guanine-G

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-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: 3’ AGC 5’ T CG TAC G C A 5’ ATG CGT 3’

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. 1. The 2 nucleotide strands separate at base pairs. • They unzip like a zipper using DNA Helicase (enzyme) 2. Each strand then builds its opposite strand by base pairing with nucleotides that float freely in the nucleus. 3. 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 New strand Original strand DNA polymerase Growth Replication fork Nitrogenous bases Replication fork New strand Original strand