Ch. 11.1: Genes are made of DNA

Ch. 11.1: Genes are made of DNAObjectives:

• Describe historic discoveries that lead to the understanding that DNA is responsible for heredity

Scientists:

Griffith, Avery, Hershey & Chase

Vocab.: virus, bacteriophageBill Nye’s Greatest Discoveries:

http://www.youtube.com/watch?v=vP_h08cT5jw

http://www.youtube.com/watch?v=p9M5xJTs-zY&feature=related

http://www.youtube.com/watch?v=x-0P_DIeHBs&feature=related

• 1928s• Result: Genetic material can be

transformed!• What molecule controls genes: Protein or

DNA?

http://www.youtube.com/watch?v=9R2Zp7IHNZo

http://www.youtube.com/watch?v=vQOdDGM5vSg&feature=related

AVERY: Determines identity of “Transforming Factor”

(enzyme that denatures proteins)

(enzyme that denatures DNA)

(Not Protein!)

Hershey & Chase: Prove DNA = Genetic material

1952: Experiments using BACTERIOPHAGE (virus that attacks bacteria)

Virus: Nucleic acid inside a protein coat (no cells)

Virus: injects its DNA into living organisms; viral DNA hijacks cells to make more viruses

Radioactively label protein coat or DNA; ONLY radioactive DNA is INSIDE DAUGHTER CELLS.

http://www.youtube.com/watch?v=YG3d77SRWZI

11.2: Structure of DNA

Objectives:

1. Identify the building blocks of DNA.

2. Describe DNA’s structure and the rules for base pairing in DNA.

Vocab: Deoxyribonucleic acid (DNA), nucleotide, Nitrogenous base, pyrimidine, purine, double helix

DNA: Deoxyribonucleic Acid

DNA structure: http://www.youtube.com/watch?v=ZGHkHMoyC5I

Bill Nye: http://www.youtube.com/watch?v=V9BZ3zx8b8I&feature=related

DNA molecule: polymer made of thousands of nucleotides.

Nucleotide: Building block (monomer)

1. 5-C sugar: Deoxyribose

2. Phosphate group

3. Nitrogen base

BasesTypes

1. Pyrimidines: single ring

• Thymine (T)

• Cytosine (C)

2. Purines: Double ring

• Adenine (A)

• Guanine (G)

Base Pairing Rules: A = T; C = G (Chargaff discovery).

H-bonds attract pairs together.

DNA StructureBackbone (Sides of “Ladder”)

1. Sugar

2. Phosphates

Rungs of Ladder

Complementary Bases

DNA Function• Store genetic info.

• Self-duplication

• Expression of genes (inherited traits)

DNA’s major function = CODE FOR PROTEINS

Double Helix

Rosalind Franklin & Maurice Wilkins (1950s)

• DNA = Helix

• X-ray crystallography to “see” structure

James Watson & Francis Crick (1950s)

• “Crack Code” …determine specifics of DNA structure.

• DOUBLE HELIX

Watson & Crick Double Helix

• 2 chains of nucleotides

• 2 strands are anti-parallel

• Backbone: sugar + phosphate

• Base pairs = rungs

DNA & Chromosomes

Prokaryotes• Circular• Very small• 1 chromo. per cell• Some enzymes &

proteins are associated w/ DNA

• Not housed in nucleus

Eukaryotes• Linear• Fairly long• Several per. Cell• Nucleosome: Loops

of DNA wrapped around histone proteins

• In nucleus

DNA OrganizationDNA is coiled around

protein histones; those coils are coiled into chromosomes.

11.3: DNA Replication

Objectives:

1. Explain how the template mechanism is important in DNA replication.

2. Describe the process of DNA replication.

Vocab: DNA Replication, DNA polymerase, semi-conservative

Template Mechanism

DNA replication is SEMI-CONSERVATIVE

New copies of DNA contain:

• 1 original strand

• 1 new strand

Each strand serves as a TEMPLATE to make a complementary copy (due to base-pairing rules)

DNA Replication:Making copies of DNA

Enzymes Involved:

1. Helicase: unwinds double helix

2. DNA Polymerase: Attaches new nucleotides; can only add to the 3’Carbon

3. Ligase: join fragmented copies on “lagging” strand.

Leading Strand: continuous growingLagging Strand: Fragmented; ligase joinsNEW STRANDS GROW in 5’ --> 3’ direction!

http://www.youtube.com/watch?v=AGUuX4PGlCc&feature=relatedhttp://www.youtube.com/watch?v=4jtmOZaIvS0