Chapter 12: Chapter 12: Molecular GeneticsMolecular Genetics

• DNA structureDNA structure

• Protein synthesisProtein synthesis

• DNA ReplicationDNA Replication

DNA: The Genetic DNA: The Genetic MaterialMaterial

Section 1 – p. 329

Warm-up:

1. DNA is what kind of macromolecule?

A. Protein

B. Lipid

C. Carbohydrate

D. Nucleic acid

2. The macromolecule, DNA, is made up of which kind of monomers?

A. Amino acids

B. Fatty acids

C. Monosaccharides

D. Nucleotides

Essential Questions1. What is DNADNA?

2. How can we describe Chargaff’sChargaff’s base pairing rules?

3. Compare the structure of a eukaryotic chromosome chromosome with prokaryote DNA.

4. How are genesgenes, chromosomes, and DNA related?

The “OLD” People of DNA

1.Fredrick Griffith

2.Oswald Avery

3.Hershey and Chase

4.Erwin Chargaff

5.Watson and Crick

Fredrick Griffith-1928

In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused pneumonia.

He isolated two different strains of pneumonia bacteria from mice and grew them in his lab.

Performed the first major experiment that led to the discovery of DNA as the genetic material

Transformation

Griffith determined that bacteria could pass genetic information from one to another.

Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease causing strain).

But what was thetransformingfactor?

Oswald Avery-1944

Oswald Avery repeated Griffith’s work to determine which molecule was most important for transformation.

Identified the molecule that transformed the R strain of bacteria into the S strain

Concluded that when the S cells were killed, DNA was released

R bacteria incorporated this DNA into their cells and changed into S cells.

Discovered that DNA was the “transforming factor”.

Hershey and Chase-1952

Alfred Hershey and Martha Chase studied viruses—nonliving particles smaller than a cell that can infect living organisms.

If Hershey and Chase could determine which part of the virus entered an infected cell, they would learn whether genes were made of protein or DNA

Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses

Provided definitive evidence that DNA is the source of genetic material.

So Griffith, Avery, Hershey and Chase all helped discover DNA and the importance that it plays in transmitting genes.

But what is DNA???

What is it made of???

What does it look like??????

Warm-up

• A nucleotide is made up of three parts. What are they? (Use your book if you like.)

What is DNA?1. A genetic code

2. A molecule made of subunits called nucleotidesnucleotides

3. A complex molecule that is arranged as a double helixdouble helix.

NUCLEOTIDESare the smallest units are the smallest units (monomers) of DNA that include:(monomers) of DNA that include:

Phosphate group

5-Carbon sugar

Nitrogen base

NUCLEOTIDES

the smallest subunit of DNA

Two Kinds of bases in DNA

Pyrimidines are single ring bases.

Thymine & Cytosine

Purines are double ring bases.

Adenine & Guanine

Memory trick “Y” are you single?

A G C T

Erwin Chargaff-

Analyzed the amounts of A, C, T, and G in DNA; Discovered A=T & C=G

The Shape of DNA is a Double Helix

DNA often is compared to a twisted ladder.

Rails of the ladder are represented by the alternating deoxyribose and phosphate.

The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

Watson and Crick

Built a model of the double helix that conformed to the others’ research

1. two outside strands consist of alternating deoxyribose and phosphate molecules

2. cytosine and guanine bases pair to each other by three hydrogen bonds

3. thymine and adenine bases pair to each other by two hydrogen bonds

Watson and Crick

Suggested the structure for DNA and hypothesized a method of replication

Refer to the DNA handoutRefer to the DNA handout

1. Locate the Phosphate groups.Phosphate groups. Label each one “PP” and color them orange.orange.

2. Locate the deoxyribose sugarsdeoxyribose sugars and label them. Color all sugars blue.blue.

3. Locate the nitrogen bases and label.

4. Label the hydrogen bonds.

DNA Structure ActivityDNA Structure Activity

1. Locate the nitrogen bases

2. Label Adenine and color it purple.Adenine and color it purple.

3. Label Thymine and color it yellow.Thymine and color it yellow.

4. Label Cytosine and color it red.Cytosine and color it red.

5. Label Guanine and color it green.Guanine and color it green.

4 Nitrogen Bases4 Nitrogen BasesPurines are

larger basesPyrimidines are

smaller bases

Adenine Thymine

Guanine Cytosine

CHARGAFF’S BASECHARGAFF’S BASE PAIRING RULES

A binds with T

G binds with C

Hydrogen Bonds

Fig. 4. Adenine-Thymine base pair with two hydrogen bounds.

Fig. 5. Guanine-Cytosine base pair with three hydrogen bounds

C = Carbon = gray N = Nitrogen = blue O = Oxygen = red

3-D Animation of DNA

http://www.umass.edu/molvis/tutorials/dna/dnapairs.htm

Stop & ReviewStop & Review1. What is the smallest subunit of DNA?

2. List 3 parts to #1?

3. What are the side chains of DNA made of?

4. What are the “steps” of DNA made of?

5. What are the base pairing rules of DNA?

6. Describe the structure of DNA in 2 words.

ANSWERS

1.Nucleotide

2.Sugar, phosphate, and a nitrogen base

3.Sugar and phosphate

4.Nitrogen base

5.A=T, C=G

6.Double Helix

Comparing eukaryote & prokaryote DNA

PROKARYOTE

Circular

EUKARYOTE

Linear

How are genesgenes, chromosomes, and DNA related?

Genes are portions of DNA that are tightly packed into chromosomes and code for the manufacture of proteins.

How are genesgenes, chromosomes and DNA related?

Think of chromosomes as socks and genes as stripes on the socks.

Place in order from smallest to largest.

Gene

DNA

Chromosomes

Vocabulary Clarification

CHROMATIN CHROMOSOME

Have Your DNA & eat it too!Have Your DNA & eat it too!

1.Collect materials

2.Follow instructions

*A (greengreen) pairs with T (pinkpink)

*C (yellowyellow) pairs with G (orangeorange)

Warm-up

1. Is DNA double stranded or single stranded?

2.If you are given the DNA sequence ATCCGTTAC, what would be the sequence of the complementary strand?