Download Bio 9C: Wednesday, 2.3.10Title: DNA Structure & Function

Bio 9C: Wednesday, 2.3.10
Title: DNA Structure & Function

Homework:
Single Block Today
 Read
pages 297-299 and take active reading notes.
 Summarize how DNA replicates!
 Read through DNA Modeling Lab

Do Now:
 Study
the diagram of Genetic Information in Cells.
 Answer the Fill-in-the-Blanks on the back of the diagram

Today’s Objectives:
 Explain
how DNA, genes, nucleotides, and chromosomes
relate to each other.
 Describe the structure of DNA.
INTRODUCTION TO GENETICS
DNA: STRUCTURE & FUNCTION
PHA Biology 9
Moretti/ Dickson
Intro to Genetics:
DNA Structure & Function



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Genetics: the study of heredity
 What determines an organism’s traits (characteristics)?
 How are traits passed on from one cell to another, and from parents to
offspring?
DNA: the molecule that carries genetic information
DNA has two important functions:
 Replicate – make exact copies of itself so it can be passed on
 Carry instructions for making proteins that determine your traits
DNA is found in all cells (in the nucleus in eukaryotic cells)
Objectives for Class:
• Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
• Describe the structure of DNA.
DNA Structure and Function
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What is it?

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Where do we find it?
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DNA = Deoxyribonucleic Acid
Found in the Nucleus
What does it do?
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
Carries your genes
Carries information to
make the proteins
that make your traits
Objectives for Class:
• Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
• Describe the structure of DNA.
DNA Structure and Function
Chromosomes
Nucleotide
Base Pairs
Another Gene: instructions for
making a different protein that
determines a different trait
DNA
Gene: Instructions for
making a protein that
determines a trait
DNA Structure
Objectives for Class:
• Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
• Describe the structure of DNA.
DNA Structure

“Building Blocks” = Nucleotide
Deoxyribose Sugar
 Phosphate
 Nitrogenous Base


Nucleotides put together:
Ladder: Uncoiled
 Double Helix: 2 long coiled strands
 Sides: alternating phosphates
& sugars


Middle/ “Rungs” of ladder:

2 Nitrogenous Bases
connected by Hydrogen bonds
Objectives for Class:
• Identify
DNA Structure: Nucleotides
Objectives for Class:
• Identify
Bio 9C: Thursday, 2.4.10
Title: DNA Structure & Function

Homework:
 Complete

Do Now:
 Read

Discussion Questions for Part I of Modeling Lab.
through the introduction of the lab
Today’s Objectives:



Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
Describe the structure of DNA.
Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Structure: Base Pairing

4 Nitrogen Bases:
 Adenine
Purine
 Guanine
 Thymine
Pyrimidine
 Cytosine
}
}

Base Pairing:
 A ---- T
 G ---- C
Objectives for Class:
• Identify
DNA Model Building Lab: Part I
Part I: Constructing DNA

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To construct your DNA model, you will need:
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18 3-prong deoxyribose centers (black pentagon)

18 phosphate straws (white tubes)

9 Hydrogen bond (white rod)
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5 Adenine (A) straws (orange)

4 Guanine (G) straws (yellow)

5 Thymine (T) straws (green)

4 Cytosine (C) straws (blue)
Build 18 nucleotides

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Record your DNA Sequence in the table

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Attaching 1 nitrogenous bases (red, blue, short green, or gray) and 1
phosphate to 1 deoxyribose center. Divide the work between partners.
Use one code letter per box. Corresponding nitrogenous bases will be
opposite each other in the table.
You will have to replicate this sequence, so make certain it is accurate.
Objectives for Class:
• Describe the structure of DNA.
DNA Structure: Images
Objectives for Class:
• Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
• Describe the structure of DNA.
DNA and Chromosomes
Chromosomes: DNA tightly
coiled around little protein balls
(histones) to make it very compact
Chromosomes
unraveling into
DNA
Nucleotide
Base Pairs
Another Gene: instructions for
making a different protein that
determines a different trait
DNA
Gene: Instructions for
making a protein that
determines a trait
DNA Replication: Overview
DNA can make an
exact copy of itself!
 Occurs every time a
cell needs to reproduce


(during S-phase of the cell cycle…)
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Replication: Overview
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
Steps of DNA Replication
1. DNA Unzips:


Enzyme breaks Hydrogen Bonds between base
pairs
Creates 2 Complementary Strands (templates)
2. DNA Polymerase moves along original strands
(templates)
 Nucleotides come from the cytoplasm
 DNA Polymerase attaches complimentary bases to
both sides of the unzipped strands (SemiConservative).
3. Completed: 2 NEW identical strands of DNA are
produced
 DNA Polymerase “proofreads” the new strands
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Replication
Note: The RED
Strand is the
Original Strand
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Model Building Lab: Part II
Part II: Replicating DNA
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Although your model is only a short portion of DNA, its
replication is the same as that of an entire chromosome
Reconstruct your original DNA Sequence.
“Unzip” your DNA sequence by “breaking” the
hydrogen bond between the two nitrogenous bases.
Observe your two separate strands. Using the other
pieces in your kit, create two new strands of DNA –
nucleotide by nucleotide.
Note that when the DNA molecule splits in half, new
complimentary bases attach to the separated strands
creating two new strands of DNA. Be sure your base
pairs match!
Be sure to construct your new DNA strand by
adding nucleotides to the original template!
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
How do we know about DNA Structure?


Chargaff: A=T and C=G
Rosalind Franklin:
Actual X-ray of DNA
 Showed double-helix structure
 Died young due to X-rays!
 Didn’t get credit for her
contributions… pretty messed up!

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Watson & Crick: Built a model
using this evidence

(They got all of the credit – initially)
Objectives for Class:
• Describe the structure of DNA.
Bio 9C: Friday, 2.5.10
Title: DNA Structure & Function


The following slides are the DNA Replication Slides with
audio explanations from 2.5.10 when Mr. Moretti was at
a conference.
Today’s Objectives:



Explain how DNA, genes, nucleotides, and chromosomes relate to each other.
Describe the structure of DNA.
Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Replication: Overview
DNA can make an
exact copy of itself!
 Occurs every time a
cell needs to reproduce


(during S-phase of the cell cycle…)
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
DNA Replication: Overview
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.
Steps of DNA Replication
1. DNA Unzips:


Enzyme breaks Hydrogen Bonds between base
pairs
Creates 2 Complementary Strands (templates)
2. DNA Polymerase moves along original strands
(templates)
 Nucleotides come from the cytoplasm
 DNA Polymerase attaches complimentary bases to
both sides of the unzipped strands (SemiConservative).
3. Completed: 2 NEW identical strands of DNA are
produced
 DNA Polymerase “proofreads” the new strands
Objectives for Class:
• Describe the structure of DNA.
• Explain WHY DNA must replicate and the 3 steps of HOW DNA replicates.