DNA Structure and Replication What is DNA u

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DNA Structure and Replication

DNA Structure and Replication

What is DNA? u DNA: • 1. molecule that has the instructions for all

What is DNA? u DNA: • 1. molecule that has the instructions for all cell activity • 2. molecule that is passed from generation to generation • 3. located in the NUCLEUS

Structure of DNA Made of Nucleotides (monomer) › Nucleotide consists of: Deoxyribose sugar (sugar)

Structure of DNA Made of Nucleotides (monomer) › Nucleotide consists of: Deoxyribose sugar (sugar) Phosphate group (phosphate) Nitrogen containing base (base) › Each human cells contains millions and millions of nucleotides that stretch to over 6 feet in length!! DNA wraps tightly around proteins to fit inside cell DNA in nucleus= 1000 feet of rope in a backpack

Review Questions 1. What makes up DNA? u 2. Where is DNA located? u

Review Questions 1. What makes up DNA? u 2. Where is DNA located? u 3. What three parts make up a nucleotide? u 4. What type of sugar is in DNA? u

Sugar-Phosphate Backbone u Sugar-Phosphate Backbone of DNA: • Formed by the sugar and phosphate

Sugar-Phosphate Backbone u Sugar-Phosphate Backbone of DNA: • Formed by the sugar and phosphate of each nucleotide bonded together • Sides of the ladder

Nitrogeneous (Nitrogen) Bases u Nitrogen Bases: Rungs or Steps of Ladder • • Adenine

Nitrogeneous (Nitrogen) Bases u Nitrogen Bases: Rungs or Steps of Ladder • • Adenine Thymine Cytosine Guanine u Adenine ALWAYS pairs with Thymine u Cytosine ALWAYS pairs with Guanine

Double Helix: The “Twisted Ladder” u Discovered by Watson and Crick u Double: Two

Double Helix: The “Twisted Ladder” u Discovered by Watson and Crick u Double: Two strands of DNA connected by nitrogen bases (hydrogen bonds) u u u Helix: Nucleotides twist together Always an equal number of A and T Always an equal number of G and C

Review Questions 1. What two parts of a nucleotide make up the “backbone”? u

Review Questions 1. What two parts of a nucleotide make up the “backbone”? u 2. How many different bases exist in DNA? What are they? u 3. What bases bond together in DNA? u 4. Why is DNA called a “double helix”? u

How Does Replication Occur? The two strands of DNA must be “unzipped” › “Unzipping”

How Does Replication Occur? The two strands of DNA must be “unzipped” › “Unzipping” occurs when the hydrogen bonds between the nitrogen bases are broken › DNA HELICASE: enzyme (protein) that breaks hydrogen bonds and unzips DNA › DNA POLYMERASE: enzyme (protein) that brings new nucleotides and attaches them to old strand Each strand is duplicated separately › New bases are brought in to complement the old (parent) strand › New strand of DNA consists of an OLD, parent strand a NEW, daughter strand

Replication 2

Replication 2

Review Questions 1. What is the first step in DNA Replication? u 2. What

Review Questions 1. What is the first step in DNA Replication? u 2. What enzyme unzips the DNA? u 3. What enzyme brings in new bases and attaches them to the old strand? u 4. What are the strands called when the new bases are added and two strands of DNA now exist? u