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 ExperimentsGriffith 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 VirusesHershey 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 StructureObjectives:
– 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 StructureEach nucleotide has 3 parts:
1. ring-shaped sugar called deoxyribose2. phosphate group3. Nitrogenous Base
Nitrogenous BasesThymine (T)Cytosine (C)Adenine (A)Guanine (G)
Thymine
Cytosine
Adenine
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.
KEY CONCEPT DNA replication copies the genetic
information of a cell.
11
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 #2New 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 Result2 Identical & Semiconservative DNA Molecules
(each molecules is …½ Original & ½ New)
Review Questions1. 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
• New nucleotides attach to complimentary nitrogen bases
• Untwists and unzips
• DNA Polymerase joins the 2 strands of DNA
2
1
3
Ribonucleic Acid (RNA)
• Objectives:– Describe differences between DNA and RNA– Describe the Nitrogenous bases found in RNA
Warm-UpTake 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
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.
11
COMPARE DNA vs. RNADNA RNA
# strands in molecule
Sugar
Nitrogen Bases
Location in cell?
When is RNA needed in the cell?
Answer = During Protein
Synthesis!!!!!
Protein SynthesisWhat 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 code2. use the mRNA code to find the correct amino acids in the protein
DNA A G C T A C G C T G G A
mRNA
Protein