Download PPT

DNA
&
the Language of
Life
Why does this cartoon make sense and sound
funny???
Lesson Overview
Identifying the Substance of Genes
Identifying the Substance of
Genes
Multiple scientists conducted experiments that helped
determine that DNA is responsible for storing,
copying, and carries genetic information. Those
scientists are:
1. Griffith – Bacterial Transformation in Mice Experiments
2. Avery – Enzyme Experiments
3. Hershey/Chase – Bacteriophage (virus) Experiments
Lesson Overview
Identifying the Substance of Genes
Griffith’s Experiments
Griffith isolated two different strains of the same
bacterial (pneumonia) species.
Here’s what he did…
Lesson Overview
Identifying the Substance of Genes
So What Happened?
…Transformation!
Some “chemical THING” was transferred from
the heat-killed cells of the S strain into the live
cells of the R strain, making the R strain deadly!
This is called Transformation.
Lesson Overview
Identifying the Substance of Genes
The Molecular Cause of
Transformation
Avery – repeated Griffith’s Transformation experiment
many times. He used enzymes to break down various cell
materials in the deadly S bacteria. The mouse only
survived when the DNA in the bacteria was broken down!
Therefore…DNA is the important molecule in Cells!!
Lesson Overview
Identifying the Substance of Genes
Bacterial Viruses
Hershey and Chase studied viruses called
Bacteriophages—nonliving particles that can infect
bacteria cells.
Bacteriophage means “bacteria-eater”
Hershey & Chase discovered that DNA
was the genetic material found in all
organisms in “genes”.
Lesson Overview
Identifying the Substance of Genes
Discovery of DNA
Scientists/Experiments
Scientist
Experiment
Conclusion
Griffith
Avery
Hershey & Chase
•
•
•
•
•
•
Bacteriophages
Bacteria Strains/Mice
DNA is genetic material found in “genes”
There is some “chemical thing” that is genetic information.
DNA is the “chemical thing” that can transform bacteria cells
Enzymes/Bacteria/Mice
DNA Structure
Objectives:
– Identify the building blocks of DNA (nucleotides)
– Describe DNA’s structure
– Use the rules for nitrogen base pairing in DNA
Preview: DNA molecules
Basics
DNA – DeoxyriboNucleic Acid
(It is a type of Nucleic Acid)
It’s Job: Stores genetic information
• Polymer made up of monomers called
Nucleotides
Discovered by Watson & Crick
DNA is a DOUBLE STRANDED molecule
• The 2 strands together form
a twisted “ladder”
• Sugar & Phosphate
Backbone makes up the sides
of the ladder
• Nitrogenous Bases (pairs)
make up the rungs of the
ladder
• Note: This picture is only 1
side of a DNA molecule!
Nucleotides
Nucleotides are the
“building blocks” or
monomers that make up
DNA
Nucleotide Structure
Each nucleotide has 3 parts:
1. ring-shaped sugar called deoxyribose
2. phosphate group
3. Nitrogenous Base
Nitrogenous Bases
Thymine (T)
Cytosine (C)
Adenine (A)
Guanine (G)
Thymine
Adenine
Cytosine
Guanine
Complementary Base Pairing Rules
Adenine (A)  Thymine (T)
Guanine (G)  Cytosine (C)
• HELD TOGETHER by HYDROGEN BONDS!
• Example:
ATG CAG TAC
Complimentary Base Pairs
(Practice)
ATC GTA ATT GCC TAG GAC TGA CTG
If we stretched out all of the DNA from all of the cells
in your body...how long would it be?
REVIEW STRUCTURE OF DNA
1. DNA is a ________ (single or double) stranded molecule.
2. DNA molecules are made up of many _____________.
3. List the 4 Nitrogenous bases in DNA:
1.
2.
3.
4.
11
KEY CONCEPT
DNA replication copies the genetic
information of a cell.
Warm - Up
We talked about 2 processes recently that
required DNA to be duplicated or copied for
them to take place.
What were those 2 processes?
Why did DNA need to be
duplicated/replicated?
Basics of DNA Replication
Why?
All cells in an organism needs the
same DNA. So, DNA must be
copied/replicated exactly before it
can be incorporated into all cells!
When does DNA Replication Occur??
During Interphase (S phase) of the
Cell Cycle!
Before Mitosis or Meiosis!
Definitions/Terms
DNA Replication – production of new DNA from
1 old DNA molecule
Semi-Conservative – Newly made DNA
molecules are ½ original DNA and ½ new DNA
Step #1
Untwist & Unzip
DNA Helicase (enzyme) “untwists” and “Unzips”
the DNA to separate the 2 strands.
Ex. Zipper on your jacket
Step #2
New Nucleotides Move In
New nucleotides move in and pair up with their
“complement” on the original DNA template
strands.
Template Strand
Template Strand
Step #3
DNA Polymerase
DNA Polymerase (enzyme) moves in and
attaches the new nucleotides to form 2
identical and Semiconservative DNA
molecules.
End Result
2 Identical & Semiconservative DNA Molecules
(each molecules is …½ Original & ½ New)
Review Questions
1. When during the cell cycle does DNA Replication occur?
• Interphase (S Phase)
2. What is the purpose of DNA replication?
• Copy/duplicate DNA in preparation for mitosis or meiosis
3. What is the FINAL PRODUCT of DNA replication?
– 2 Identical Semiconservative DNA molecules
4. Put the following “steps” of the DNA replication process in
order
2
1
3
• New nucleotides attach to complimentary nitrogen bases
• Untwists and unzips
• DNA Polymerase joins the 2 strands of DNA
Ribonucleic Acid (RNA)
• Objectives:
– Describe differences between DNA and RNA
– Describe the Nitrogenous bases found in RNA
Warm-Up
Take a good look at the
RNA molecule to
the right…
List:
• 2 ways it is
different from
DNA
•
2 ways it is similar
to DNA
11
RNA is different from DNA in 3 major ways:
1. RNA has a ribose sugar.
2. RNA has uracil instead of thymine.
3. RNA is a single-stranded molecule.
COMPARE DNA vs. RNA
DNA
# strands in molecule
Sugar
Nitrogen Bases
Location in cell?
RNA
When is RNA needed in the
cell?
Answer =
During Protein
Synthesis!!!!!
Protein Synthesis
What is the purpose?
MAKES PROTEINS!!!
What are the steps??
1. TRANSCRIPTION - DNA code is
used to make mRNA in the
nucleus
2. TRANSLATION – In the
cytoplasm, a ribosome uses RNA
to make a protein by putting
together amino acids!
Amoeba Sisters Video
Let’s make a protein from a gene!!!
Steps:
1. make mRNA from the DNA code
2. use the mRNA code to find the correct amino acids in the protein
DNA 
mRNA 
Protein 
A G C
T A C
G C T
G G A