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.

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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.

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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